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SINTEF REPORT TITLE Blowout and Well Release Characteristics and Frequencies, 2006 AUTHOR(S) Per Holand, ExproSoft CLIENT(S) SINTEF Technology and Society Safety and Reliability Address: NO-7465 Trondheim, NORWAY Location: S P Andersens veg 5 Telephone: +47 73 59 27 56 Fax: +47 73 59 28 96 Enterprise No.: NO 948 007 029 MVA Multiclient REPORT NO. CLASSIFICATION CLIENTS REF. STF50 F06112 Restricted Espen Fyhn Nilsen, Statoil CLASS. THIS PAGE ISBN PROJECT NO. NO. OF PAGES/APPENDICES Unrestricted 504016 77/0 ELECTRONIC FILE CODE PROJECT MANAGER (NAME, SIGN.) CHECKED BY (NAME, SIGN.) \\Phantom\es201016\BLOWOUT\TEKST 2006\Annual report 2006 final.doc Per Holand Lars Bodsberg FILE CODE DATE APPROVED BY (NAME, POSITION, SIGN.) 2006-10-05 Lars Bodsberg ABSTRACT This report is based on the 2006 Version of the SINTEF Offshore Blowout Database. The report gives an overview of offshore blowout and well release characteristics and frequencies. Blowout data from the US Gulf of Mexico Outer Continental Shelf, the Norwegian waters, and the UK waters from the period 1980-01-01 until 2005-01-01 have been focused on. KEYWORDS ENGLISH NORWEGIAN GROUP 1 Marine Technology Marin Teknikk GROUP 2 Offshore Offshore SELECTED BY AUTHOR Risk Risiko Blowout Utblåsning Frequencies Frekvenser

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SINTEF REPORT TITLE

Blowout and Well Release Characteristics and Frequencies, 2006

AUTHOR(S)

Per Holand, ExproSoft

CLIENT(S)

SINTEF Technology and Society Safety and Reliability

Address: NO-7465 Trondheim, NORWAY Location: S P Andersens veg 5 Telephone: +47 73 59 27 56 Fax: +47 73 59 28 96 Enterprise No.: NO 948 007 029 MVA

Multiclient

REPORT NO. CLASSIFICATION CLIENTS REF.

STF50 F06112 Restricted Espen Fyhn Nilsen, Statoil CLASS. THIS PAGE ISBN PROJECT NO. NO. OF PAGES/APPENDICES

Unrestricted 504016 77/0 ELECTRONIC FILE CODE PROJECT MANAGER (NAME, SIGN.) CHECKED BY (NAME, SIGN.) \\Phantom\es201016\BLOWOUT\TEKST 2006\Annual report 2006 final.doc Per Holand Lars Bodsberg FILE CODE DATE APPROVED BY (NAME, POSITION, SIGN.)

2006-10-05 Lars Bodsberg ABSTRACT

This report is based on the 2006 Version of the SINTEF Offshore Blowout Database. The report gives an overview of offshore blowout and well release characteristics and frequencies. Blowout data from the US Gulf of Mexico Outer Continental Shelf, the Norwegian waters, and the UK waters from the period 1980-01-01 until 2005-01-01 have been focused on.

KEYWORDS ENGLISH NORWEGIAN

GROUP 1 Marine Technology Marin Teknikk GROUP 2 Offshore Offshore SELECTED BY AUTHOR Risk Risiko

Blowout UtblåsningFrequencies Frekvenser

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PREFACE

This report is based on the SINTEF Offshore Blowout Database, version 2006. The intention of the report is to give an overview of blowout/well release characteristics and frequencies, and not to analyse and evaluate the different blowout types. The format of the report is similar to the report that was issued last year. Appendix 1 to the Users Manual (and also the Help file) for the SINTEF Offshore Blowout Database list criteria used for the database fields in general. The Users Manual/help file has been updated to reflect some recent changes in the database categorizing. Some key updates from 2005 version Exploration wells Exploration wells have now been separated in Appraisal wells and Wildcat wells in the exposure data after 1980 for the areas US GoM OCS, UK waters, and Norwegian waters. The exploration blowouts and well releases have also been re-categorised to reflect this change. To differ between the Wildcats and Appraisal wells the following were assumed; - For Norwegian waters the NPD classification has been used as it is. - For the UK waters all wells classified as Exploration wells are regarded as Wildcats,

while the wells classified as Appraisal wells are of regarded as Appraisals. - For the US GoM OCS a different approach has been used. All exploration wells drilled in

certain areas are numbered from 1 and further, where well number 1 is the first well drilled. For the US GoM OCS all exploration wells numbered as 1 have been regarded as Wildcats, while all the other wells are regarded as Appraisal wells. This may be inaccurate, but this will likely lead to an underestimation of no. of Wildcats compared to no. of Appraisal wells for the US GoM OCS.

Exposure data The general exposure data has been updated also to include the 2004 exposure data. Exploration Wildcat wells vs. exploration Appraisal wells have been given some more focus. The water depth related exposure data has also been updated. This year also data from the UK waters has also been included. Deleted Blowouts No blowouts have been deleted from the database this year. New Blowouts Six new blowouts/well releases have been added to the database (ID547 – ID552). They were observed for the following countries and years:

• US GoM OCS, three incidents, they were from 1994, 2003 and 2005 • Australia, one incident from 1991 • US GoM NOT OCS, one incident from 1998 • Azerbaijan, one incident from 2005

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Edited Blowouts Twenty-four blowouts/well releases have been significantly edited. Table 0.1 shows where and when these blowouts/ell releases occurred. Table 0.1 Edited blowouts and well releases

Incident Id Number Country Year of

occurrence 207 Norway 1981 350 Norway 1985 431 Norway 1996 532 UK 2001 503 US/GoM not OCS 1999 192 US/GoM OCS 1980 197 US/GoM OCS 1980 217 US/GoM OCS 1981 237 US/GoM OCS 1983 265 US/GoM OCS 1984 269 US/GoM OCS 1985 324 US/GoM OCS 1989 386 US/GoM OCS 1991 369 US/GoM OCS 1993 390 US/GoM OCS 1993 425 US/GoM OCS 1996 420 US/GoM OCS 1997 460 US/GoM OCS 2000 463 US/GoM OCS 2000 476 US/GoM OCS 2001 502 US/GoM OCS 2001 518 US/GoM OCS 2002 544 US/GoM OCS 2005 545 US/GoM OCS 2005

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LIST OF CONTENTS PREFACE..............................................................................................................................................................3

1. ABOUT THE DATABASE ..............................................................................................................................7 1.1 PARTICIPANTS ...............................................................................................................................................7 1.2 DATABASE STRUCTURE.................................................................................................................................7 1.3 IMPORTANT DEFINITIONS ..............................................................................................................................9 1.4 CATEGORY AND SUB-CATEGORY.................................................................................................................10 1.5 PHASE OF OPERATION ..................................................................................................................................11 1.6 NORTH SEA STANDARDS .............................................................................................................................11

2. OVERVIEW OF BLOWOUTS/WELL RELEASES INCLUDED IN THE DATABASE........................13 2.1 INTRODUCTION............................................................................................................................................13 2.2 DATA QUALITY ...........................................................................................................................................13 2.3 OVERVIEW OF COUNTRIES REPRESENTED IN THE DATABASE.......................................................................14 2.4 DURING WHAT OPERATIONAL PHASES DO BLOWOUTS/WELL RELEASES OCCUR? .......................................16 2.5 NO. OF BLOWOUTS/WELL RELEASES PER YEAR ...........................................................................................17

3. BLOWOUTS VS. WELL RELEASES..........................................................................................................19

4. OVERALL BLOWOUT/WELL RELEASE EXPERIENCE......................................................................21 4.1 BLOWOUT/WELL RELEASE VS. FLOW MEDIUM............................................................................................21 4.2 BLOWOUT/WELL RELEASE VS. FLOW-RATES ...............................................................................................22 4.3 SEVERITY ....................................................................................................................................................22 4.4 IGNITION OF BLOWOUTS/WELL RELEASES...................................................................................................22 4.5 BLOWOUT/WELL RELEASE DURATION.........................................................................................................24 4.6 BLOWOUT/WELL RELEASE FLOW-PATHS AND RELEASE POINTS ..................................................................25 4.7 BLOWOUT/WELL RELEASE CAUSES.............................................................................................................29 4.8 OPERATIONS AND ACTIVITIES WHEN BLOWOUT/WELL RELEASE OCCURS ...................................................33 4.9 EXPLORATION WILDCATS VS. EXPLORATION APPRAISAL WELLS.................................................................36 4.10 BLOWOUTS FROM AUSTRALIA, CANADA EAST COAST, THE NETHERLANDS, AND US/CALIFORNIA OCS...37

5. “NORMAL” DRILLING AND PRODUCTION EXPOSURE DATA.......................................................39 5.1 DRILLING EXPOSURE DATA .........................................................................................................................39

5.1.1 US GoM OCS .....................................................................................................................................39 5.1.2 United Kingdom .................................................................................................................................41 5.1.3 Norway ...............................................................................................................................................41 5.1.4 The Netherlands .................................................................................................................................44 5.1.5 Canadian East Coast..........................................................................................................................45 5.1.6 US Pacific OCS ..................................................................................................................................46 5.1.7 Australia .............................................................................................................................................47 5.1.8 Denmark .............................................................................................................................................47 5.1.9 Compiled Drilling Exposure Data......................................................................................................48

5.2 PRODUCTION EXPOSURE DATA ...................................................................................................................50 5.2.1 US GoM OCS .....................................................................................................................................50 5.2.2 United Kingdom .................................................................................................................................50 5.2.3 Norway ...............................................................................................................................................51 5.2.4 US Pacific OCS ..................................................................................................................................52 5.2.5 Compiled Production Exposure Data.................................................................................................53

6. VARIOUS EXPOSURE DATA .....................................................................................................................55 6.1 WELL DEPTH RELATED EXPOSURE DATA....................................................................................................55

6.1.1 US GoM OCS Wells............................................................................................................................55 6.1.2 Norwegian Wells ................................................................................................................................57

6.2 WATER DEPTH RELATED DRILLING EXPOSURE DATA .................................................................................58 6.3 SHUT-IN WELLHEAD PRESSURE RELATED EXPOSURE DATA........................................................................62

6.3.1 US GoM OCS Drilling Wells..............................................................................................................62

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6.3.2 Norwegian Drilling Wells .................................................................................................................. 64 6.3.3 US GoM OCS Wells in Production.................................................................................................... 65

6.4 PRODUCTION RATES AND GAS OIL RATIO DATA, US GOM OCS................................................................ 66 6.4.1 Production Rates ............................................................................................................................... 66 6.4.2 Gas Oil Ratio ..................................................................................................................................... 68

6.5 WORKOVER FREQUENCY EXPOSURE DATA ................................................................................................ 69 6.6 WIRELINE FREQUENCY EXPOSURE DATA.................................................................................................... 70 6.7 COILED TUBING AND SNUBBING EXPOSURE DATA...................................................................................... 71

7. OVERALL BLOWOUT/WELL RELEASE FREQUENCIES .................................................................. 73

REFERENCES ................................................................................................................................................... 77

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1. About the Database

1.1 Participants

The SINTEF Offshore Blowout Database was initiated in 1984. By the end of 2005 the following companies were sponsoring the database: - Norsk Hydro a.s. - Statoil - Total E&P Norge - Shell Research Limited - BP Norge - Safetec A/S - Scandpower Risk Management AS - DnV - Chevron Energy Technology Company - Lilleaker Consulting a.s - Eni Norge AS - ConocoPhillips Norge

1.2 Database Structure

The blowout database resides in a Microsoft Access 2000 data file named blowout.mdb. The main programming tool used is Microsoft Visual Basic 6.0. The Seagate Crystal Reports version 8.5 is used for making all the reports from the program. The SINTEF Offshore Blowout Database includes blowout/well release descriptions, drilling and production exposure data for certain areas in the world. Blowout/ well release descriptions The database contains 51 different fields describing each blowout/well release. The various fields are grouped in six different groups. They are:

1. Category and location 2. Well description 3. Present operation 4. Blowout causes 5. Blowout Characteristics 6. Other

Category and location Includes information related to the incident category (blowout vs. well leak), offshore installation such as location, operator, installation name and type, and water depth.

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Well description Includes well and casing depths, last casing size, mud weight, bottom hole- and shut in pressure, GOR, formation age and rock type. Present operation Includes the phase (exploration drilling, development drilling, workover etc.), the operation presently carried out (for example casing running) and the present activity (for example cementing) Blowout causes Include external cause (stating if an external cause contributed to the incident), loss of the primary barrier, loss of the secondary barrier (describing how primary and secondary barrier were lost) and human error. It should be noted that the field regarding human error in general holds low quality information. Human errors are frequently masked. A field named North Sea standards highlights if the development of the blowout could have been avoided if North Sea type equipment had been used (for instance in other parts of the world a blind shear ram is not required in surface BOP stacks) Blowout characteristics Twelve fields are included comprising flow-path, flow medium, flow-rate (low quality), release point, ignition type, time to ignition, lost production (low quality), duration, fatalities, consequence class, material loss and pollution Other In the Other screen five fields is included, they are: control method, remarks (includes a description of the incident, data quality (includes an evaluation of the source data quality), last revision date and references. Exposure data The various areas represented with exposure data area shown in Table 1.1. Table 1.1 Overview of exposure data included in the database

Country Drilling exposure data Production exposure data US GoM OCS Yes Yes Norway Yes Yes United Kingdom Yes Yes The Netherlands Yes No Canada East Coast Yes No Australia Yes No US Pacific Yes Yes Denmark Yes No

Search possibilities and reporting facilities Almost any type of search may be performed to select specific blowout /well release event types. Search criteria may be established by selecting predefined codes, specific numeric values, specific free text, or any combinations of these. The predefined codes are spelled out to ease understanding.

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The database program counts and presents the events satisfying the search criteria. The selected data may be viewed, printed or copied to separate files for further analyses, for example by database or spreadsheet programs. The exposure data and the blowout data are not linked. Blowout frequencies can therefore not directly be established.

1.3 Important Definitions

The following main definitions have been utilised when categorising the blowouts/well releases in categories and sub-categories. Blowout definition NPD came up with a blowout definition in their proposal for the new regulations. (“Aktivitetsforskriften, eksternt høringsutkast av 3.7.2000, høringsfrist 3.11.2000”). Med utblåsing som nevnt i denne paragrafen første ledd, menes formasjonsfluid som strømmer ut av brønnen eller mellom formasjonslagene etter at alle definerte tekniske brønnbarrierer eller operasjon av disse har sviktet.

Translated to English the definition will be: A blowout is an incident where formation fluid flows out of the well or between formation layers after all the predefined technical well barriers or the activation of the same have failed.

The definition does however not seem to have become a part of the final new NPD regulation, but remains the database blowout definition. Well release definition: The reported incident is a well release if oil or gas flowed from the well from some point were flow was not intended and the flow was stopped by use of the barrier system that was available on the well at the time the incident started. Shallow gas definition: Any gas zone penetrated before the BOP has been installed. Any zone penetrated after the BOP is installed is not shallow gas (typical Norwegian definition of shallow gas).

All shallow gas incidents in the database have at the extent possible been categorised according to the typical Norwegian definition of shallow gas. This definition is not relevant for all US GoM incidents because:

� US GoM OCS reservoirs vary highly in depth. Some reservoirs were as shallow as 200 meters.

� For some incidents they had sat a full BOP stack, but had now intention to use it because it would likely cause a blowout outside the casing and a possible crater.

� For some incidents they had drilled very deep without running an extra casing string and the BOP.

� And for some incident they had used a combination of a BOP and a diverter.

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Further, for many of the incidents the description of the incident in the sources is insufficient, and some assumptions have to be made. A general comment is that it is not easy to categorise all the incidents in shallow and deep incidents because of the above.

1.4 Category and Sub-category

The categories and subcategories utilised when classifying the incidents in the SINTEF Offshore Blowout Database are shown in Table 1.2. Table 1.2 Main categories and subcategories for the incidents in the SINTEF Offshore Blowout

database Main Category Sub category Comments/Example

1. Totally uncontrolled flow, from a deep zone

Totally uncontrolled incidents with surface/subsea flow.

2. Totally uncontrolled flow, from a shallow zone

Typical the diverter system fails

Blowout (surface flow)

3. Shallow gas “controlled” subsea release only

Typical incident is that riserless drilling is performed when the well starts to flow. The rig is pulled away

4. Underground flow only Blowout (underground flow)

5. Underground flow mainly, limited surface flow

The limited surface flow will be incidents were a minor flow has appeared, but typical the BOP has been activated to shut the surface flow

6. Limited surface flow before the secondary barrier was activated

Typical incident will be that flow is through the drillpipe and the shear ram is activated

Well release

7. Tubing blown out of well, then the secondary barrier is activated

Typical incident occurring during completion or workover. Shear ram is used to close the well after the tubing has been blown out of the well.

Diverted well release

8. Shallow gas controlled flow (diverted)

All incidents were the diverter system functioned as intended.

Blowout and well release

Unknown Unknown Unknown may be selected for both the category and the subcategory

The list of sub-categories, shown in Table 1.2, may be extended if found appropriate. One option will be to split the sub category for Well release further down to highlight incidents with an ignition potential.

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1.5 Phase of operation

Each of the blowout/well releases in the database is categorised in the phase of operation they occurred. Table 1.3 shows the pre-set codes used for phase of operation. Table 1.3 Phase of operation

Description Remarks COMPLETION Activities associated to well completion activities DEV.DRLG Development drilling EXPL.DRLG Exploration drilling, includes wildcats and appraisal wells PRODUCTION Production, injection, closed in wells UNKNOWN DRLG When it is not known whether it is DEV.DRLG or EXPL.DRLG UNKNOWN Unknown WIRELINE Wireline operations in connection with a production/injection well, not wireline

operations carried out as a part of well drilling, well completion or well workover WORKOVER Workover activities, not including wireline operations. Snubbing and coiled tubing

operations

1.6 North Sea Standards

The intention with the field North Sea Standards is to identify blowout/well release incidents that likely would have been prevented in North Sea operations because the procedures or equipment utilised when the incident occurred are different from North Sea equipment or procedures. Table 1.4 presents the coding used for this field. Table 1.4 North Sea standards

Description Yes No, no shear ram No, BOP not North Sea standard No, two barrier principle not followed Sometimes not relevant, BOP removed to install casing seal Unknown Not evaluated

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2. Overview of Blowouts/Well releases Included in the Database

2.1 Introduction

The SINTEF Offshore Blowout Database does per January 2006 include information about 524 offshore blowouts/well releases that have occurred world-wide since 1955. The number of blowouts/well releases related to the different periods is presented in Table 2.1 Table 2.1 Number of blowouts/well releases related to the different periods

Period No. of blowouts/well releases 1950-ties 9 1960-ties 54 1970-ties 114 1980-ties 176 1990-ties 112 2000 - 2006 65 Total 530

Blowouts/well releases that have occurred in the period 1980-01-01 - 2005-01-01 in US GoM OCS, UK, and Norway are focused on. Blowouts/well releases that have occurred after 2005-01-01 are not included in this report at all. Blowouts/well releases from before 1980 and the rest of the world are only briefly included. The database structure and coding are presented in "SINTEF Offshore Blowout Database, Version 4.0”, User's Manual, September 2006” and the help file for the database program.

2.2 Data Quality

SINTEF's intention is to collect data from all occurring blowouts. However, it is a fact that many blowouts/well releases occurring in this period have never been recorded in the database. This because, public sources, which are the main source of information for blowouts/well releases occurring outside US GoM OCS, and UK, and Norway, do frequently not describe blowouts/well releases with small consequences. Therefore, several blowouts/well releases are believed to be missing from the database. It is SINTEF's belief that from 1980-01-01 most blowouts occurring in the US Gulf of Mexico (GoM) Outer Continental Shelf (OCS), the UK, and Norway have been included in the database. The quality of data related to blowouts occurring after 1970-01-01 is significantly better than the data from before 1970. However, for many blowouts the quality still is low because proper descriptions of the incidents are lacking. Blowout information is frequently hidden from the public.

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For each of the blowout/well release records in the database the quality of the source material is given. Table 2.2 shows an overview of the data quality for the blowouts/well releases that have occurred in the period 1980-01-01 – 2005-01-01. Table 2.2 Quality of blowout/well release data source material

Quality of blowout/well release data source material

All blowouts except US GoM OCS, UK, and Norwegian blowouts in the

period 1980-01-01 – 2005-01-01

Only US GoM OCS, UK, and Norwegian blowouts in the period 1980-01-01 –

2005-01-01 Very good 7 55 Good 9 44 Fair 19 51 Low 32 39 Very low 72 20 Total 139 209

2.3 Overview of Countries Represented in the Database

In Table 2.3 shows an overview of the number of blowouts and well releases for the countries represented in the database.

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Table 2.3 Overview of countries represented in the database

COUNTRY 50-ties

60-ties

70-ties

80-ties

90-ties

1Jan 00 - 31 Dec 04

later than 1 Jan 05 Total

ANGOLA 1 1 AUSTRALIA 2 1 1 1 5 AZERBAIJAN 3 1 4 BRAZIL 3 1 4 BRUNEI 2 1 1 4 BURMA 1 1 CABINDA 1 1 2 CANADA EAST 2 2 CANADA NORTH 1 2 3 CHINA 1 1 1 3 CONGO 1 2 3 DENMARK 1 1 DUBAI 2 1 3 EGYPT 3 2 5 EQUATORIAL GUINEA 1 1 ETHIOPIA 1 1 GABON 1 1 GERMANY 1 1 INDIA 3 5 8 INDONESIA 4 11 2 4 21 IRAN 1 4 7 1 13 ITALY 1 1 1 3 LIBYA 1 1 MALAYSIA 1 2 3 MEXICO 2 6 2 1 11 NETHERLANDS 1 1 NIGERIA 3 3 2 1 9 NORWAY 3 13 10 2 28 PAPUA NEW GUINEA 1 1 2 PERU 2 2 PHILLIPPINES 1 1 QATAR 2 2 SAUDI ARABIA 1 3 1 5 SOUTH KOREA 1 1 SPAIN 1 1 TAIWAN 2 2 THAILAND 2 2 TRINIDAD 4 1 1 2 8 UK 4 1 8 11 4 28 UNKNOWN 1 1 US 1 1 2 US/ALASKA State 1 3 1 5 US/CALIFORNIA OCS 1 1 3 5 US/CALIFORNIA state 2 2 US/GOM NOT OCS 2 5 17 7 9 5 45 US/GOM OCS 6 30 58 77 52 32 4 259 USSR 2 6 8 VENEZUELA 3 1 4 VIETNAM 1 1 YUGOSLAV 1 1 Total 9 54 114 176 112 60 5 530

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2.4 During what Operational Phases do Blowouts/Well Releases Occur?

In Table 2.4 and Table 2.5 no. of blowouts/well releases have been related to the operational phases. Table 2.4 No. of blowouts/well releases experienced during different operational phases

(including all blowouts/well releases until 2005-01-01) PERIOD Dev.

drlg Expl. drlg

Unk. drlg

Compl-etion

Work-over

Produ-ction

Wireline Un-known

Total

Before 1980 43 75 1 12 18 20 3 5 17724.3% 42.4% 0.6% 6.8% 10.2% 11.3% 1.7% 2.8%

1980 to 2005-01-01 87 123 7 21 52 36 8 14 34825.0% 35.3% 2.0% 6.0% 14.9% 10.3% 2.3% 4.0%

Total 130 198 8 33 70 56 11 19 52524.8% 37.7% 1.5% 6.3% 13.3% 10.7% 2.1% 3.6%

Table 2.5 Area specific overview of no. of blowouts/well releases experienced during different operational phases (including all blowouts/well releases 01-01-1980 - 2005-01-01)

Production AREA Dev. drlg

Expl. drlg **

Unk. drlg

Comp-letion

Work-over External

cause* No ext. cause*

Wire-line

Un-known

Total Total excl. ext.

cause* 7 25 2 3 6 1 1 3 48 47UK, and Norw-

egian waters 14.6% 52.1% 4.2% 6.3% 12.5% 2.1% 2.1% 6.3% 100.0%50 46 12 31 6 9 5 2 161 155US GoM OCS

31.1% 28.6% 7.5% 19.3% 3.7% 5.6% 3.1% 1.2% 100.0%30 52 5 6 15 10 9 12 139 129Rest of the

world 21.6% 37.4% 3.6% 4.3% 10.8% 7.2% 6.5% 8.6% 100.0%Total 87 123 7 21 52 17 19 8 14 348 331

25.0% 35.3% 2.0% 6.0% 14.9% 4.9% 5.5% 2.3% 4.0% 100.0%* External causes are typical; storm, military activity, ship collision, fire and earthquake. ** One of the Expl. drilling blowouts in the "rest of the world” was caused by volcanic activities When reading Table 2.5, it is important to note that the most thorough data is from the US GoM OCS, UK, and Norway. In the US GoM OCS they have experienced a relatively high no. of blowouts/well releases during development drilling compared to exploration drilling. This is explained by the fact that in US GoM OCS they are drilling relatively more development wells than exploration wells, compared to UK and Norway. Further, the relatively high no. of well workover blowouts/well releases in US GoM OCS area does indicate that the number of workovers in that area is high. It should, further, be noted that external loads caused approximately 50% of the production blowouts. External causes are discussed in Section 4.7, on page 29.

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2.5 No. of Blowouts/Well releases per Year

In Table 2.6 shows a year-to-year overview of no. of blowouts/well releases for US GoM OCS, UK, and Norway in the period 1980-01-01 - 2005-01-01. Table 2.6 Year to year overview of no. of blowouts/well releases for US GoM OCS, UK, and

Norway in the period 1980-01-01 – 2005-01-01 Expl. Drlg Production Year Dev.

Drlg App- raisal

Wild- cat

Un- known

Un-known drilling

Comp-letion

Work-over External

cause* No ext. cause*

Wire-line

Un-known

Total

1980 2 1 2 1 2 1 91981 2 2 5 2 111982 5 1 4 1 111983 7 2 3 1 1 141984 1 6 1 81985 2 2 6 2 121986 1 1 21987 1 2 1 1 2 1 81988 1 3 1 1 61989 4 5 2 3 2 1 171990 3 2 2 3 1 111991 4 1 3 1 1 101992 2 1 1 1 3 81993 2 2 1 51994 1 1 1 1 41995 1 1 2 41996 1 2 2 1 61997 3 4 2 2 111998 3 1 1 1 2 1 91999 3 2 52000 3 2 3 1 1 1 112001 3 1 1 1 4 1 112002 2 1 1 1 1 62003 1 1 1 1 1 52004 1 2 2 5Total 57 24 45 2 2 15 37 10 7 8 2 209

* External causes are typical; storm, military activity, ship collision, fire and earthquake.

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3. Blowouts vs. Well Releases

As explained in Section 1.4 on page 10 the incidents in the database has been categorised in blowouts and well releases. When excluding the blowouts with external causes the database includes 202 blowouts/well releases for the US GoM OCS, Norway and UK in the period January 1980 until January 2005. Table 3.1 shows an overview of the no. of blowouts/well releases within the main phases of operation, categories and sub categories. Table 3.1 Overview of the no. of incidents within the main phases of operation, categories and

sub categories for US GoM OCS, Norway and UK blowouts/well releases in the period Jan. 1980 until Jan. 2005

Incident category Sub category

According to North Sea standard? (See

Table 1.4 page11)

Dev. drlg

Expl. drlg

Unk. drlg

Compl-etion

Work-over

Prod-uction

Wire-line

Un-known Total

Yes 6 1 7Shallow gas "controlled" subsea release only Total 6 1 7

No, no acoustic backup BOP control system 1 1

No, no shear ram 1 3 5 7 16No, two barrier principle not followed 1 1 2

Sometimes not relevant, BOP removed to install casing seal

2 1 1 4

Unknown 1 2 3 1 7Yes 4 15 3 9 6 3 40

Totally uncontrolled flow, from a deep zone

Total 8 22 9 20 6 4 1 70No, BOP not North Sea standard 1 1

Sometimes not relevant, BOP removed to install casing seal

1 1

Yes 21 16 1 38

Totally uncontrolled flow, from a shallow zone

Total 22 17 1 40

Blowout (surface flow)

Total 30 45 1 9 20 7 4 1 117Underground flow mainly, limited surface flow Yes 1 2 3

Underground flow only Yes 3 5 1 1 10

Blowout (underground flow)

Total 4 7 1 1 13Shallow gas controlled flow (diverted) Yes 16 9 25Diverted

well release Total 16 9 25

Limited surface flow before the secondary barrier was activated

Yes 5 8 1 5 10 2 4 35

Other Yes 1 1 2String blown out of well, then the secondary barrier is activated

Yes 1 1 7 9

Well release

Total 7 9 1 6 17 2 4 46Unknown Yes 1 1Unknown Total 1 1

Total all 57 71 2 15 37 10 8 2 202

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4. Overall Blowout/Well Release Experience

4.1 Blowout/Well Release vs. Flow Medium

Table 4.1 shows an overview of the blowout/well release flow medium for the different incidents. Only US GoM OCS, UK, and Norwegian incidents in the period 1980-01-01 - 2005-01-01 are included. Table 4.1 Blowout/well release flow medium for US GoM OCS, UK, and Norway in the period

1980-01-01 - 2005-01-01 Incident category Flow medium Dev.

Drlg Expl. Drlg

Unk. Drlg

Comp-letion

Work-over

Prod-uction*

Wire-line

Un-known

Total

Condensate, Gas (deep) 2 4 1 7Condensate, Gas (deep), water 1 1Gas (deep) 2 15 8 10 2 37Gas (deep), Mud, Water 1 1Gas (deep), Water 1 1Oil 1 1Oil, Gas (deep) 2 1 1 4 3 2 13Oil, Gas (deep), H2S 1 1Oil, Gas (deep), Mud 1 1Oil, Gas (deep), Water 1 1 2Shallow water 1 1Shallow gas 18 17 1 36Shallow gas H2S 1 3 4Shallow gas, Water 1 3 1 5Shallow, unknown fluid 1 1Unknown 1 1 1 3Water 1 1 2

Blowout (surface flow)

Total 30 45 1 9 20 7 4 1 117Condensate, Gas (deep) 1 1Gas (deep) 2 4 6Oil, Gas (deep) 1 1 2Shallow gas 1 1Unknown 1 1 2Water 1 1

Blowout (underground flow)

Total 4 7 1 1 13Shallow gas 14 7 21Shallow gas, Mud 1 1 2Shallow gas, Water 1 1 2

Diverted well release

Total 16 9 25Gas (deep) 1 1Unknown Total 1 1Condensate, Gas (deep) 1 1Condensate, Gas (deep), water 1 1Gas (deep) 2 3 1 6Gas (deep), Methanol 1 1Gas (deep), Mud 2 1 3Gas (gas lift gas) 1 1Gas (trapped gas) 1 1Mud 1 1 2 1 5Oil 1 1Oil, Gas (deep) 1 1 8 1 11Oil, Gas (deep), Mud 2 1 3Oil, Water 1 1Shallow gas 1 2 3Shallow gas, Mud 1 1Unknown 1 1 1 3 1 7

Well release

Total 7 9 1 6 17 2 4 46Total 57 71 2 15 37 10 8 2 202

* Blowouts caused by external loads are excluded (storm, military activity, ship collision, fire and earthquake). ** Stems from a blowout outside the casing from a shallow zone during production

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4.2 Blowout/Well Release vs. Flow-rates

The blowout/well release flow-rates from the actual incidents described in the database are poorly documented. For some blowouts flow-rate figures exist, but for most blowouts they do not exist. The database has, however, three fields that describe the flow-rates during well tests for the actual well or close by wells. These fields are Gas volume, Oil volume and Water volume. Flow-rates are important figures in risk and environment analyses. To establish a realistic distribution of flow-rates to expect for specific fields, field specific productivity data should be compared to blowout/well release experience with respect to remaining restrictions in the wells during the blowout/well release situations. For several blowouts/well releases there are significant flow restrictions that will reduce the flow.

4.3 Severity

The blowout/well release database contains a specific field describing blowout/well release severity. The quality of the information in this field is relatively low. These data are therefore not presented in this report. However, it should be noted that most of the blowouts/well releases do cause relatively small damages.

4.4 Ignition of Blowouts/Well Releases

In Table 4.2 and Table 4.3 experienced data related to ignition of blowouts/well releases are presented. Only incidents from the period 1980-01-01 - 2005-01-01 have been included. It has been chosen to separate US GoM OCS, UK, and Norwegian blowouts/well releases from the rest of the world. Blowouts caused by external loads (storm, fire etc. are not included) Please note that it should not be differed between ignition probability for an oil blowout/well release and a gas blowout, because for oil blowouts the volume of gas blowing is very high compared to the volume of oil blowing.

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Table 4.2 Experienced ignition for US GoM OCS, UK, and Norwegian blowouts/well releases in the period 1980-01-01 - 2005-01-01. Blowouts caused by external loads (storm, fire etc.) are not included

Delayed ignition PHASE Deep or

shallow No

ignition Immediate

ignition (<5 mins)

5 mins – 1 hour

1 hour –6 hrs

6 hrs – 24 hrs >24 hrs

Total

Blowout (surface flow) Deep 5 2 1 8 Dev.drlg Shallow 16 2 2 1 1 22 Deep 16 2 4 22 Expl.drlg Shallow 22 1 23

Unknown drlg Shallow 1 1 Completion 6 2 1 9 Workover 15 1 1 1 2 20 Production 7 7 Wireline 4 4 Unknown 1 1

93 9 3 2 7 3 117 Total 79.5% 7.7% 2.6% 1.7% 6.0% 2.6% 100.0% Blowout (underground flow)

Deep 3 3 Dev.drlg Shallow 1 1 Expl.drlg Deep 7 7 Production 1 1 Unknown 1 1

13 13 Total 100.0% 100.0% Well release

Deep 5 5 Dev.drlg Shallow 1 1 2 Deep 7 7 Expl.drlg Shallow 2 2

Unknown drlg Deep 1 1 Completion 6 6 Workover 16 1 17 Production 2 2 Wireline 4 4

44 2 46 Total 95.7% 4.3% 100.0% Diverted well release

Shallow 16 16 Dev.drlg Expl.drlg Shallow 8 1 9

24 1 25 Total 96.0% 4.0% 100.0% Unknown Expl.drlg Deep 1 1

1 1Total 100.0% 100.0% 175 11 4 2 7 3 202 All blowouts/well

releases 86.6% 5.4% 2.0% 1.0% 3.5% 1.5% 100.0%

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Table 4.3 Experienced ignition for rest of the world (US GoM OCS, UK, and Norway are not included) blowouts/well releases in the period 1980-01-01 - 2005-01-01. Blowouts caused by external loads are not included.

Ignited blowouts PHASE No ign-ition Immediate ign-

ition (<5mins) Delayed ignition

Unknown Total

Development drilling 15 11 4 30 Exploration drilling 35 8 5 3 51 Unknown drlg 2 1 2 5 Completion 1 4 1 6 Workover 8 4 3 15 Production 5 1 3 9 Unknown 6 3 3 12

72 32 18 6 128 Total 56.3% 25.0% 14.1% 4.7% 100.0%

If comparing Table 4.2 and Table 4.3, far more ignited blowouts/well releases in the material for the "rest of the world". The main reason is probably that from "rest of the world" blowouts with small consequences are more seldom reported.

4.5 Blowout/Well Release Duration

In Table 4.4 the experienced blowout/well release duration is presented. Only US GoM OCS, UK, and Norwegian blowouts/well releases in the period 1980-01-01 - 2005-01-01 have been included. Blowouts caused by external loads (storm, fire etc.) are not included. It should be noted that bridged or depleted are listed as primary cause for regaining well control for 30 out of the 45 exploration drilling Blowout (surface flow), and 13 of the 30 development drilling Blowout (surface flow).

For the diverted well releases (both exploration and development drilling) bridged or depleted are listed as primary cause for regaining well control for 13 out of the 25 well releases.

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Table 4.4 Blowout/well release duration for US GoM OCS, UK, and Norwegian blowouts/well releases in the period 1980-01-01 - 2005-01-01. Blowouts caused by external loads (storm, fire etc.) are not included

Phase Shallow or deep T ≤10 mins 10min < T ≤

40min 40min < T ≤

2 hrs 2 hrs < T ≤ 12 hrs

12 hrs < T ≤ 2 days

2 days < T ≤ 5 days

T > 5days

Un-known Total

Blowout (surface flow) Deep 1 2 1 1 1 2 8 Dev.drlg Shallow 3 2 4 4 4 5 22 Deep 1 2 6 4 4 5 22 Expl.drlg Shallow 1 2 4 2 7 4 3 23

Unknown drlg Shallow 1 1 Completion 1 3 1 4 9 Workover 1 4 8 2 4 1 20 Production 4 1 1 1 7 Wireline 1 2 1 4 Unknown 1 1

1 2 7 17 29 20 22 19 117 Total 0.9% 1.7% 6.0% 14.5% 24.8% 17.1% 18.8% 16.2% 100.0%Blowout (underground flow)

Deep 1 1 1 3 Dev.drlg Shallow 1 1 Expl.drlg Deep 1 1 4 1 7 Production 1 1 Unknown 1 1

1 1 1 7 3 13 Total 7.7% 7.7% 7.7% 53.8% 23.1% 100.0%Diverted well release Dev.drlg Shallow 2 3 4 3 1 1 2 16 Expl.drlg Shallow 1 1 4 2 1 9

2 4 5 7 3 2 2 25 Total 8.0% 16.0% 20.0% 28.0% 12.0% 8.0% 8.0% 100.0%Well release

Deep 2 3 5 Dev.drlg Shallow 1 1 2 Deep 5 1 1 7 Expl.drlg Shallow 1 1 2

Unknown drlg Deep 1 1 Completion 5 1 6 Workover 9 1 1 2 4 17 Production 2 2 Wireline 2 2 4

25 2 1 3 2 1 12 46 Total 54.3% 4.3% 2.2% 6.5% 4.3% 2.2% 26.1% 100.0%Unknown Expl.drlg Deep 1 1

1 1Total 100.0% 100.0%

28 8 13 28 35 23 30 37 202 Total all blowouts/well releases 13.9% 4.0% 6.4% 13.9% 17.3% 11.4% 14.9% 18.3% 100.0%

4.6 Blowout/Well Release Flow-paths and Release Points

In Table 4.5 – Table 4.7 the experienced release point vs. the final blowout/well release flow paths for the various phases of operation are presented. Only US GoM OCS, UK, and Norwegian blowouts/well releases in the period 1980-01-01 – 2005-01-01 have been included. Blowouts caused by external loads (storm, fire etc.) are not included.

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Table 4.5 Release point vs. final flow-path for drilling shallow gas blowouts and well releases Final flow-path ⇒Incident main

type Release point ⇓

Through drill

string

Through annulus

Through outer

annulus

Outside casing

Under-ground

flow

Un-known Total

Blowout (surface flow) Diverted, BOP valve outlet 1 1 Diverted, subsea - outside casing 1 1 Diverter syst.leak 1 1 2 Diverter syst.leak - line eroded 1 1 Diverter syst.leak - line parted 2 2 Diverter syst.leak - main divert 1 1 Drillfloor - through rotary 2 1 3 From wellhead 7 7 Subsea - outside casing 3 3 Subsea wellhead 1 1 Blowout (surface flow) total 7 10 4 1 22 Blowout (underground flow) From wellhead 1 1 Blowout (underground flow) total 1 1Diverted well release Diverted 14 2 16 Diverted well release total 14 2 16 Well release Drillfloor - through rotary 1 1 From wellhead 1 1 Well release total 1 1 2

Development drilling shallow gas incidents

Dev.drlg total 22 13 4 1 1 41 Blowout (surface flow) Diverter syst.leak 2 2 Diverter syst.leak - line eroded 3 3 Diverter syst.leak - line parted 1 1 Drillfloor - through rotary 1 1 Drillfloor - top of drill string 1 1 From wellhead 1 1 Subsea - outside casing 4 4 Subsea crater 1 1 Subsea wellhead 8 8 Unknown 1 1 Blowout (surface flow) total 1 14 2 5 1 23 Diverted well release Diverted 9 9 Diverted well release total 9 9Well release Subsea wellhead 1 1 2 Well release total 1 1 2

Exploration drilling shallow gas incidents

Expl.drlg total 1 24 3 5 1 34 Blowout (surface flow) Subsea wellhead 1 1 Blowout (surface flow) total 1 1

Unknown drilling shallow gas incidents Unknown drlg total 1 1

Total all shallow gas incidents 1 47 16 9 1 2 76

Most shallow gas blowouts/well releases have their final flow-path through the well bore annulus. The flow is either diverted without any problems, the diverter system fails, or the flow is released through the subsea wellhead.

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Table 4.6 Release point vs. final flow-path for “deep” drilling blowouts and well releases Incidentmain type

Final flow-path ⇒Release point ⇓

Through drill

string

Through test

string

Through annulus

Throughouter

annulus

Outside casing

Under-ground blowout

Un-known Total

Blowout (surface flow) Drillfloor - choke manifold 1 1 Drillfloor - through rotary 1 1 From wellhead 2 2 4 Subsea - outside casing 1 1 Unknown 1 1 Blowout (surface flow) total 5 2 1 8Blowout (underground flow) No surface flow 3 3 Blowout (underground flow) total 3 3Well release Drillfloor - through rotary 1 2 3 Subsea - outside casing 1 1 Unknown 1 1Well release total 1 2 1 1 5

Develop-ment drilling deep

Total 1 7 2 2 3 1 16 Blowout (surface flow) Bop valve outlet 1 1 Diverter syst.leak - line parted 1 1 Drillfloor - through rotary 2 1 3 Drillfloor - top of drill string 1 1 2 From wellhead 2 3 5 Shaker room 1 1 Subsea - outside casing 5 5 Subsea BOP 1 1 Subsea BOP (choke line flexible) 1 1Subsea crater 1 1 Subsea wellhead 1 1 Blowout (surface flow) total 1 10 4 7 22 Blowout (underground flow) No surface flow 5 5 Subsea - outside casing 1 1 Unknown 1 1 Blowout (underground flow) total 1 5 1 7Well release Diverted 1 1 Drillfloor - through rotary 3 3 Drillfloor - top of drill string 2 2 Drillfloor - tubing valve 1 1 Well release total 2 1 4 7Unknown Unknown 1 1 Unknown total 1 1

Explor- ation drilling deep

Total 3 1 14 4 8 5 2 37 Well release Drillfloor - through rotary 1 1 Well release total 1 1

Unknown Drilling deep

Total 1 1

TOTAL ALL DEEP 3 2 22 6 10 8 3 54

Through annulus is the most common final flow-path for both exploration and development drilling “deep” blowouts/well releases. Forty percent of the deep drilling blowouts/well releases was flowing through the annulus. Ten incidents came outside the casing, causing subsea releases. One of them also ignited when the gas reached the surface. In general subsea releases are more frequent for exploration well blowouts than for development well blowouts. This was also observed for the shallow gas blowouts. Ten incidents only caused underground flow. Probably more of these incidents occur than reported in the database.

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Table 4.7 Release point vs. final flow-path for completion, workover, production and wireline blowouts and well releases

Phase Final flow-path ⇒Release point ⇓

Through coiled tubing

Through drill

string

Through tubing

Through annulus

Through outer

annulus

Outside casing

Under-ground blowout

Total

Blowout (surface flow) Drillfloor - drill pipe valve 1 1Drillfloor - through rotary 1 1Drillfloor - top of drill string/tubing 3 2 5From x-mas tree (choke body) 1 1Mud room 1 1Blowout (surface flow) total 4 4 1 9Well release Drillfloor - through rotary 3 3Drillfloor - top of tubing 2 2Shaker room 1 1Well release total 1 2 3 6

Comp- letion

COMPLETION TOTAL 5 6 4 15Blowout (surface flow) BOP valve outlet 4 4Drillfloor - through rotary 2 2Drillfloor - top of drill string 4 4Drillfloor - top of tubing 1 2 3Drillfloor - tubing valve 1 1From wellhead 1 1 2From x-mas tree 1 1Mud room 1 1Subsea - outside casing 1 1Unknown 1 1Blowout (surface flow) total 1 5 3 9 1 1 20Well release BOP valve outlet 1 1Drillfloor - through rotary 1 8 9Drillfloor - top of drill string 1 1Drillfloor - top of tubing 2 2From above x-mas tree 1 1 2From x-mas tree 1 1 2Well release total 6 11 17

Work- over

WORKOVER TOTAL 1 5 9 20 1 1 37Blowout (surface flow) From wellhead 1 1 1 3From x-mas tree 1 1Subsea - outside casing 1 1Subsea crater 1 1Subsea x-mas tree 1 1Blowout (surface flow) total 3 1 1 2 7Blowout (underground flow) No surface flow 1 1Blowout (underground flow) total 1 1Well release From x-mas tree 2 2Well release total 2 2

Prod- uction

PRODUCTION TOTAL 5 1 1 2 1 10Blowout (surface flow) Drillfloor - wireline stuffing box/BOP 1 1From above x-mas tree 2 2From x-mas tree 1 1Blowout (surface flow) total 3 1 4Well release From above x-mas tree 2 2From x-mas tree 1 1Unknown 1 1Well release total 4 4

Wire- line

WIRELINE TOTAL 7 1 8Blowout (surface flow) From wellhead 1 1Blowout (surface flow) total 1 1Blowout (underground flow) No surface flow 1 1Blowout (underground flow) total 1 1

Unknown

UNKNOWN TOTAL 1 1 2Total 1 10 27 25 4 3 2 72

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Most blowouts during completion result in flow through the tubing or the drill string/work string. It is important to note that for several of these blowouts the BOP stack did not include a blind-shear ram (Table 3.1 on page 19). With a blind-shear ram these blowouts could have been stopped at an earlier stage, and they would in many cases not have been categorised as a blowout. It is not mandatory to use blind-shear rams in US OCS surface BOPs. The normal flow-paths for workover blowouts/well releases are either through the drill string/tubing or through the annulus. It is important to note that for several of these blowouts the BOP stack did not include a blind-shear ram (Table 3.1 on page 19). Further, the drill string/tubing blowouts are mostly released from the top of the drill string/tubing hanging in the rotary table slips. Annulus blowouts do mostly come through the rotary. Wireline blowouts typically flow through the tubing and the release point is above the X-mas tree. Eight of the ten production blowouts came to the air in the wellhead/X-mas tree area. The last two came outside casing at the sea bottom, one of them caused a crater.

4.7 Blowout/Well Release Causes

Normally to experience a blowout, at least one primary and one secondary barrier have to fail. For drilling, workover and completion blowouts the primary barriers are usually the hydrostatic pressure from the mud column and the secondary barrier is the mechanical barriers, either subsea or on the installation. For production wells the primary and secondary barriers are mechanical barriers. It should be noted that when drilling in shallow zones there is normally only one blowout barrier. The installations do, however, have means for forcing the gas away from the installation. In this report those means are treated as a secondary barrier. The blowout database does contain fields for describing the blowout/well release causes, i.e. why were the primary and secondary barrier lost? Further, the database contains one field that describes whether the blowout/well release was "caused" by an external load. Out of the 209 blowouts/well releases from US GoM OCS, UK, and Norway in the period 1980-01-01 - 2005-01-01, seven were "caused" by an external load (Table 2.6, page 17). It is, however, important to note that an external load normally only ruins the topside barrier. To experience a blowout, the downhole barrier also has to fail. So an external load will not be the single blowout cause. Typically the external load ruins the wellhead/X-mas tree barriers of an active well, and the downhole barrier fails to activate or is leaking.

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Table 4.8 shows an overview of blowouts caused by external loads. Table 4.8 Overview of blowouts caused by external loads for US GoM OCS, UK, and Norway in

the period 1980-01-01 - 2005-01-01 Water

depth (m) Phase Oper-ation Activity External

cause Primary barrier Secondary barrier Flow-medium

6Prod-uction

Closed in gas well

Well closed in

Ship collision

C5.SCSSV/storm choke failure (Not enough surge to close valve)

A8.X-mas tree failed (leakage between tubing head flanges and master valve)

Oil, Gas (deep)

143 Prod-uction

Produc-ing oil Gas lifting Fire/-

explosion

C5.SCSSV/storm choke failure & C4.Tubing to annulus communication, equipment or nipple failure (5 to 6 wells failed)

A8.X-mas tree failed (all trees failed due to topside fire)

Oil, Gas (deep)

12 Prod-uction

Produc-ing gas

Regular production

Ship collision

C5.SCSSV/storm choke failure (not installed?)

A8.X-mas tree failed (due to collision)

Oil, Gas (deep)

10 Prod-uction

Produc-ing oil

Regular production Storm

C5.SCSSV/storm choke failure (Assumed, may also have been a tubing annulus communication)

A8.X-mas tree failed (damaged by storm) Oil

13 Prod-uction

Produc-ing oil

Regular production Storm

C5.SCSSV/storm choke failure (Assumed, may also have been a tubing annulus communication)

A8.X-mas tree failed (damaged by storm) Oil

10 Prod-uction

Produc-ing oil

Regular production Storm

C5.SCSSV/storm choke failure (Assumed, may also have been a tubing annulus communication)

A8.X-mas tree failed (damaged by storm) Oil

15 Prod-uction

Produc-ing oil

Regular production Storm C5.SCSSV/storm choke failure B4.Wellhead failed

(hurricane damage) Oil

Table 4.9 and Table 4.10 show the different causes for loosing the primary and secondary barriers, as reported in the database.

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Table 4.9 Primary barrier failure causes listed in the database for the US GoM OCS, UK, and Norwegian blowouts/well releases in the period Jan. 1980 - Jan. 2005

Dev.drlg Expl.drlg Unk. drlg Cate-gory PRIMARY BARRIER FAILURE Deep Shal. Deep Shal. Deep Shal.

Comp-letion

Work-over

Prod-uction

Wire-line

Unk-nown

Total

Too low mud weight 2 3 3 2 3 13Annular losses 1 1 2 1 1 6While cement setting 3 9 4 2 1 19Trapped gas 1 1Swabbing 6 2 3 2 4 17Gas cut mud 2 2 4Improper fill up 1 1 2Disconnected riser 1 1 2Unexpected high well pressure 1 3 5 1 10Reservoir depth uncertainty 1 1 2Cement preflush weight too low 1 1

Too low hyd. head

Unknown why 1 3 2 4 1 1 12Poor cement 1 1 1 1 4Formation breakdown 1 1 2Stripper bop failure 1 1Snubbing equipment failure 4 4X-mas tree failure 1 1

tubing leakage 1 1 2Tubing to annulus communication equipm./nipple 1 1 2SCSSV/storm choke failure 1 4 5Well test string barrier failure 1 1Wireline stuffing box failure 1 1Wireline lubricator failure 2 2Packer plug failure 1 1Tubing plug failure 1 1 2Unknown 1 1 2Total no. of primary barrier failures 8 23 23 23 1 9 20 7 4 1 119Incidents with two prim. barrier failures 1 1 2

Blow-out (sur-face flow)

No. of blowouts (surface flow) 8 22 22 23 1 9 20 7 4 1 117Too low mud weight 1 1 2Annular losses 1 1While cement setting 1 1Unexpected high well pressure 1 1 2

Too low hyd. head

Unknown why 1 2 3Tubing leakage 1 1Unknown 2 1 3

Blow-out (under-ground flow)

No. of blowouts (underground flow) 3 1 7 1 1 13Too low mud weight 1 2 3Annular losses 4 1 5While cement setting 3 1 4Swabbing 9 9Unexpected high well pressure 1 4 5

Too low hyd. Head

Unknown why 1 1Total no. of primary barrier failures 18 9 27Incidents with two prim. barrier failures 2 2

Divert-ed well release

No. of diverted well releases 16 9 25Too low mud weight 1 1 2Annular losses 1 1Drilling into neighbour well 1 1Trapped gas 1 5 6Swabbing 1 1 1 3 2 8Gas cut mud 1 1Unexpected high well pressure 3 1 1 5

Too low hyd. Head

Unknown why 1 1 1 3Poor cement 1 1 2Coil tubing failure 1 1Snubbing equipment failure 2 2X-mas tree failure 1 1Tubing burst 1 1SCSSV/storm choke failure 2 1 2 5Well test string barrier failure 1 1 2Wireline lubricator failure 1 1Packer plug failure 1 1Other 2 1 3Unknown 1 1 2Total no. Of primary barrier failures 5 2 7 2 1 6 19 2 4 48Incidents with two prim. barrier failures 2

Well release

No. of well releases 5 2 7 2 1 6 17 2 4 46Unknown 1 1Un-

known No. of unknown incidents 1 1Total 16 41 37 34 1 1 15 37 10 8 2 202

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Table 4.10 Secondary barrier failure causes listed in the database for the US GoM OCS, UK, and Norwegian blowouts/well releases in the period Jan. 1980 - Jan. 2005.

Dev.drlg Expl.drlg Unk. drlg Cate-gory SECONDARY BARRIER FAILURE Deep Shal. Deep Shal. Deep Shal.

Compl-etion

Work-over

Prod-uction

Wire-line

Unk-nown Total

String safety valve failed 1 1 2 4String safety valve not available 1 1 2 4Failed to stab kelly valve 1 3 3 7SCCSV/storm choke failed 1 1X-mas tree failed 1 4 2 7Failed to close BOP 1 1 1 2 6 11Diverted - no problem 1 1Failed to operate diverter 3 3Diverter failed after closure 7 1 8 16Drilling without riser 1 5 6Disconnected riser 1 1Annulus valve failed 1 1Not sufficient frictional backpressure 1 1BOP failed after closure 2 1 5 1 9BOP/diverter not in place 3 4 3 1 1 12Wellhead failed 1 1Casing head failed 1 1 2Tubing to annulus communication 1 1Poor cement 3 3 6Casing valve failure 1 1Wellhead seal failed 1 1 2Inner casing failed 1 1Fracture at csg shoe 2 4 6Casing leakage 1 4 1 1 2 9Formation breakdown 1 1 2Not relevant 1 1Not relevant - only one barrier present 1 2 1 2 6Unknown 1 1 1 3Total no. of secondary barrier failures 8 24 25 25 1 10 20 7 4 1 125Incidents with two sec. barrier failures 2 3 2 1 8

Blow-out (sur-face flow)

Blowout (surface flow) total 8 22 22 23 1 9 20 7 4 1 117Failed to close BOP 1 1Diverted - no problem 1 1Fracture at csg shoe 1 1 1 3Casing leakage 2 1 3Formation breakdown 1 1 2Unknown 1 3 1 5Total no. of secondary barrier failures 3 2 8 1 1 15Incidents with two sec. barrier failures 1 1 2

Blow-out (under-ground flow)

Blowout (underground flow) total 3 1 7 1 1 13Diverted - no problem 16 9 25Divert-

ed well release Diverted well release total 16 9 25

String safety valve failed 1 1 2String safety valve not available 1 1Failed to stab kelly valve 2 1 3Wireline bop/lubricator not installed 1 1SCCSV/storm choke failed 1 1 2X-mas tree failed 1 1 1 3Coiled tubing stuffing box failed 1 1Failed to close BOP 2 1 1 2 1 7Diverted - no problem 1 1Drilling without riser 1 1Not sufficient frictional backpressure 1 1 1 6 9BOP failed after closure 1 1Wellhead failed 1 1Wellhead seal failed 1 1 2Outer casing failed 1 1Fracture at csg shoe 1 1Not relevant 1 1 2 4Other 1 1Unknown 1 1 1 1 4

Well release

Well release total 5 2 7 2 1 6 17 2 4 46Unknown 1 1Un-

known Unknown total 1 1Total no. of incidents 16 41 37 34 1 1 15 37 10 8 2 202

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4.8 Operations and Activities when Blowout/Well Release Occurs

In Table 4.11 to Table 4.16 an overview of the operations and activities in progress when the blowouts/well releases occurred is presented for the various operational phases. The data is from the US GoM OCS, UK, and Norwegian blowouts/well releases in the period 1980-01-01 - 2005-01-01. Table 4.11 Operations and activities in progress when the shallow gas blowouts/well releases

occurred

Drilling activity Casing running

Other/unknownoperations Total Operation ⇒

Activity ⇓ Dev. Expl. Unk. drlg Dev. Expl. Dev. Expl. Dev. Expl. Unk.

drlg Total

BLOWOUT (SURFACE FLOW) Actual drilling 2 10 1 2 10 1 13Well suspended 1 1 1Tripping out 6 2 6 2 8Out of hole 1 1 1Coring 1 1 1Milling (and reaming) 1 1 1Cementing casing 1 1 1 1 2Wait on cement 9 2 9 2 11Install BOP 1 1 1Nipple down BOP 1 1 1Changing equipment 1 1 1Wait on weather 1 1 1Unknown 1 2 1 1 2 3 5Total no. of activities 9 17 1 11 3 3 3 23 23 1 47No. of blowouts listed with two activities 1 1 1No. of blowouts (surface flow) 9 17 1 10 3 3 3 22 23 1 46BLOWOUT (UNDERGROUND FLOW) Wait on cement 1 1 1No. of blowouts (underground flow) 1 1 1DIVERTED WELL RELEASE Actual drilling 2 5 2 5 7Tipping out 8 1 8 1 9Circulating 1 1 1Casing running 2 2 2Cementing casing 1 1 1Wait on cement 3 3 3Unknown 1 1 2 2No. of diverted well releases 11 6 5 1 2 16 9 25WELL RELEASE Actual drilling 1 1 1Tripping out 1 1 1Leak off test 1 1 1Unknown 1 1 1No. of well releases 1 1 1 1 2 2 4TOTAL ALL SHALLOW INCIDENTS 21 24 1 17 4 3 6 41 34 1 76

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Table 4.12 Operations and activities in progress when the “deep” drilling blowouts/well releases occurred

Drilling activity

Casing running

Other/unknown operations Total Operation ⇒

Activity ⇓ Dev. Expl. Dev. Expl. Dev. Expl.Unk. Drlg Dev. Expl.

Unk. Drlg Total

Blowout (surface flow) Actual drilling 1 10 1 10 11 Tripping out 3 3 3 Out of hole 1 1 1 Casing running 1 1 1 Cementing casing 1 1 1 Wait on cement 3 4 3 4 7 Install bop 1 1 1 Nipple down BOP 2 2 2 Actual well test 1 1 1 Unknown 1 1 1 1 2 3 Pull wireline 1 1 1 Total no. of activities 2 15 4 8 2 1 8 24 32 No. of blowouts listed with two activities 2 2 2No. of blowouts (surface flow) 2 15 4 6 2 1 8 22 30 Blowout (underground flow) Actual drilling 3 3 3 3 6 Unknown 1 3 4 4 No. of blowouts (underground flow) 3 4 3 3 7 10 Well release Actual drilling 4 4 4 Tripping out 1 1 1 Gravel pack 1 1 1 Circulating 1 1 1 Pulling casing 1 1 1 Pull/drill out well plugs 1 1 1 1 2 Actual well test 1 1 1 1 2 Maintenance surface equipment 1 1 1 Unknown 1 1 1 Total no. of activities 4 2 1 6 1 5 7 1 14 No. of blowouts listed with two activities 1 1No. of well releases 4 2 1 5 1 5 7 1 13 Unknown UNKNOWN 1 1 1 No. of unknown incidents 1 1 1TOTAL ALL DEEP INCIDENTS 9 21 4 6 3 10 1 16 37 1 54

Table 4.13 Operations and activities in progress when the completion blowouts/well releases occurred

Operation ⇒Activity ⇓

Running wellequipment

Well testingincl.prepare Circulating Perforating Coiled

tubingOther/

unknown Total

Blowout (surface flow) Tripping out 2 2 Circulating 1 1 Killing 1 1 Perforating 1 1 Gravel pack 2 2 Other, bleed off pressure above SCSSV 1 1 Unknown 1 1 No. of blowouts(surface flow) 3 2 1 3 9Well release Tripping out 1 1 2 Tripping in 1 1 Flow check 1 1 Perforating 1 1 Gravel pack 1 1 Maintenance well equipment 1 1 Total no. of activities 1 2 1 1 2 7No. of well releases listed with two activities 1 1No. of well releases 1 1 1 1 1 6Total no. of incidents 4 1 2 2 1 5 15

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Table 4.14 Operations and activities in progress when the workover blowouts/well releases occurred

Operation ⇒

Activity ⇓

Pulling well

equip- ment

Runningwell

equip- ment

Installingequip- ment

Well testing

incl. prepare

Circu-lating

Snubb-ing

Coiledtubing

Perfor-ating

Aban-don well

Total

BLOWOUT (SURFACE FLOW) Tripping out 2 2Tripping in 1 1Out of hole 1 1Circulating 1 1 2Pulling casing 1 1Cement squeeze 1 1Set well plug 1 1Pull tubing 1 1 2Perforating 1 1Gravel pack 1 1Cleaning well 1 1 2Coiled tubing operations 1 1Snubbing in 1 2 1 4Unknown 1 1Total no. of activities 5 1 2 1 2 3 4 1 2 21No. of blowouts listed with two activities 1 1No. of blowouts (surface flow) 5 1 2 1 2 3 3 1 2 20WELL RELEASE Circulating 1 1Install BOP 1 1Pull/drill out well plugs 1 1Nipple down x-mas tree 1 1Snubbing out 2 2Pull tubing 6 1 7Acidizing 1 1Run coiled tubing 1 1Coiled tubing operations 1 1Changing equipment 1 1No. of well releases 7 2 2 2 1 3 17Total no. of incidents 12 1 4 1 2 5 5 2 5 37

Table 4.15 Operations and activities in progress when the production blowouts/well releases occurred

Operation ⇒Activity ⇓

Producing oil

Producing condensate

Producing gas

Closed in gas/-condensate well

Unknown Total

BLOWOUT Regular production 1 3 1 5 Failure diagnosing 2 2 No. of blowouts 1 3 2 1 7BLOWOUT (UNDERGROUND FLOW) Failure diagnosing 1 1

No. of blowouts (underground flow) 1 1WELL RELEASE Regular Production 2 2

No. of well releases 2 2TOTAL NO. OF INCIDENTS 1 2 3 3 1 10

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Table 4.16 Operations and activities in progress when the wireline blowouts/well releases occurred

Operation ⇒Activity ⇓

Rigging up wireline equipment

Running wireline operations

Total

BLOWOUT (SURFACE FLOW) Run wireline 2 2 Pull wireline 1 1 Logging 1 1

No. of blowouts 4 4WELL RELEASE Changing Equipment 1 1 Run wireline 2 2 Unknown 1 1 No. of well releases 1 3 4Total no. of incidents 1 7 8

The blowout listed with “Unknown” as Phase was a Blowout (underground flow) with no information related to operation and activity.

4.9 Exploration Wildcats vs. Exploration Appraisal Wells

The exploration wells for the US GoM OC, UK waters and Norwegian waters have now been categorized in exploration wildcats and exploration appraisal wells. Table 4.17 Table 4.17 Exploration wildcats and Exploration appraisal wells in the database for the US GoM

OCS, UK, and Norwegian blowouts/well releases in the period Jan. 1980 - Jan. 2005

Main category Shallow or deep Exploration well type No of incidents Appraisal 9 Deep

Wildcat 13 Appraisal 8 Wildcat 14

Blowout (surface flow) Shallow

Unknown 1 Blowout (surface flow) total 45 Blowout (under-ground flow) Deep Wildcat 7 Blowout (underground flow) total 7

Appraisal 2 Diverted well release Shallow Wildcat 7

Diverted well release total 9Appraisal 3 Wildcat 3 Deep Unknown 1 Appraisal 1

Well release

Shallow Wildcat 1 Well release total 9Unknown Deep Appraisal 1 Unknown total 1Total all exploration incidents 71

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4.10 Blowouts from Australia, Canada East Coast, The Netherlands, and US/California OCS

Exposure data from from Australia, Canada East Coast, The Netherlands and US/California OCS has been included in this report (Section 5). The associated blowouts and well releases are, however, not included in the previous chapters of the report. Table 4.18 and Table 4.19 list key data for the observed blowouts in these areas in the period 1980-01-01 - 2005-01-01. Table 4.18 Key data for blowouts observed blowouts/well releases for the Canadian East Coast,

Dutch waters, and Australian waters Id_no 405 259 266 268 548 Country Netherlands Canada East Coast Canada East Coast Australia Australia Phase Production Expl.drlg Expl.drlg Production Expl.drlg Category Blowout (surface

flow) Blowout (surface flow)

Blowout (underground flow)

Blowout (surface flow)

Blowout (underground flow)

Sub category Totally uncontrolled flow, from a deep zone

Totally uncontrolled flow, from a deep zone

Underground flow only

Totally uncontrolled flow, from a deep zone

Underground flow only

Date 15-May-83 22-Feb-84 20-Sep-84 17-Dec-84 07/02/1991 Flow medium Gas (deep) Condensate, Gas

(deep) Gas (deep) Oil, Gas (deep) Gas (deep)

Ignition type NO NO NO NO NO Duration days 10 10 270 10Unknown Loss of primary barrier

C3.Tubing to annulus communication - tubing leakage

C14.Casing plug failure (HP zone isolating bridge plug broke at 5200 meters)

A8.Too low hyd. head - unexpected high well pressure

C4.Tubing to annulus com-munication - equipm./nip-ple failure (assumed)

A15.Too low hyd. head - unknown why

Loss of secondary barrier

D2.Casing leakage B1.Failed to close BOP (First annular, obstruction in BOP,then S/R,- to little power to cut, then acoustic close failed)

D2.Casing leakage D2.Casing leakage (assumed)

D3.Formation breakdown

Operation P2.Producing gas D4.Well testing (preparing to test shallow zone)

D1.Drilling activity P1.Producing oil Unknown

Activity P1.Regular production

B1.Circulating A7.Fishing P1.Regular production

Unknown

Data quality Fair Very good Fair Very low Low

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Table 4.19 Key data for blowouts observed blowouts/well releases for the US California OCS Id_no 449 475 482 539 Country US/California OCS US/California OCS US/California OCS US/California OCS Phase Workover Workover Dev.drlg Workover Category Well release Well release Well release Blowout (surface flow) Sub category Limited surface flow

before the secondary barrier was activated

Limited surface flow before the secondary barrier was activated

Shallow gas controlled flow (diverted)

Totally uncontrolled flow, from a deep zone

Date 7-Mar-98 19-Nov-00 24-Mar-01 18/11/2004 Flow medium Gas (deep), Water Oil, Water Mud Gas (deep) Ignition type NO NO NO NO Duration days Unknown Unknown 0.0104

(15 mins) 0.1042 (2.5 hrs)

Loss of primary barrier

A15.Too low hyd. head - unknown why

C13.Tubing plug failure A10.Too low hyd. head - annular losses

A10.Too low hyd. head - annular losses. (Stop pumping for 30 minutes for removal of lock down pin)

Loss of secondary barrier

Not relevant Not relevant B10.Diverted - no problem

B4.Wellhead failed (removed lock down pin)

Operation W1.Pulling well equipment

W1.Pulling well equipment

D1.Drilling activity W3.Installing equipment

Activity A2.Tripping out D6.Pull/drill out well plugs

Unknown G4.Maintenance surface equipment

Data quality Fair Low Good Very good

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5. “Normal” Drilling and Production Exposure Data

The exposure date in this section of the report includes yearly well drilling and no. of wells in production for some specific areas. The offshore drilling wells are from Norway, UK, US GoM OCS, East Coast of Canada and the Netherlands. The production data stems from Norway, UK, and US GoM OCS. The format of the exposure data varies for the different areas.

5.1 Drilling Exposure Data

5.1.1 US GoM OCS The drilling exposure data for the US GoM OCS stems from a computerised list of all wells drilled (/1/). A version from August 2006 was used for this report. The file includes information on borehole activities such as drilling activity, counts on the number of boreholes completed, and number of shut-in's. Additional information includes the lease number, well name, and spud date, the well class, surface area/block number, well depths, and statistics on well status summary. Per August 2006 the data-file includes information from more than 46000 wells drilled all time in the US GoM OCS. The number of wells drilled in the US GoM OCS area is presented in Table 5.1.

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Table 5.1 Number of drilled wells in US GoM OCS area Exploration wells

Wildcat* Appraisal* Total Development wells

Spud year

All wells inc.

sidetracks

Side-tracked wells

All wells inc.

sidetracks

Side-tracked wells

All wells inc.

sidetracks

Side-tracked wells

Completed wells**

All wells inc.

sidetracks

Side-tracked wells

Completed wells**

1980 129 4 232 19 361 23 104 807 79 529 1981 147 8 190 13 337 21 99 870 98 571 1982 190 20 202 21 392 41 112 838 83 560 1983 177 13 204 26 381 39 112 762 116 511 1984 327 33 229 26 556 59 161 755 131 511 1985 295 28 216 39 511 67 147 662 120 439 1986 149 16 106 16 255 32 77 433 93 286 1987 196 23 200 28 396 51 116 448 84 301 1988 302 34 230 45 532 79 154 452 101 302 1989 220 31 235 38 455 69 132 511 101 348 1990 276 34 214 32 490 66 141 566 180 377 1991 164 21 166 19 330 40 98 430 127 285 1992 106 14 109 14 215 28 57 329 103 223 1993 175 20 170 39 345 59 98 570 202 385 1994 217 26 200 34 417 60 120 589 221 379 1995 187 31 189 50 376 81 110 675 293 431 1996 249 38 190 49 439 87 127 697 308 463 1997 272 52 249 70 521 122 153 837 430 565 1998 268 81 228 100 496 181 149 641 381 446 1999 200 55 170 70 370 125 121 662 367 462 2000 223 53 217 52 440 105 146 937 602 659 2001 229 56 182 56 411 112 123 852 544 531 2002 173 43 135 35 308 78 112 633 358 337 2003 200 62 154 57 354 119 114 539 306 309 2004 198 55 164 66 362 121 132 553 300 322

Total 5269 851 4781 1014 10050 1865 3013 16048 5728 10530 * To differ between Wildcats and Appraisal wells the following has been assumed; All exploration wells drilled in certain areas

are numbered from 1 and further, where well number 1 is the first well drilled. For US GoM OCS all exploration wells numbered as 1 have been regarded as Wildcats, while all the other wells are regarded as Appraisal wells. This may be inaccurate, but this will likely lead to an underestimation of no. of Wildcats compared to no. of Appraisal wells for the US GoM OCS

** In the 2000 version and earlier versions of this report the number of completed wells as listed in the source file was used directly for this column. Closer investigation showed that when a production well is abandoned it would be re-categorized to abandoned. This will lead to an underestimation of number of completed wells. To adjust the figure to a more correct number 30 % of all exploration wells and 70% of all development wells are assumed to be completed each year for the whole period 1980 – 1999. These figures stems from the average in the period 1992 – 1997.

As seen from Table 5.1 many of the US GoM wells are side-tracked. The wells in the Gulf of Mexico are primarily side-tracked for deflecting the direction of the borehole to encounter an alternate target horizon or potential productive interval at a selected aerial location. Deviation of a well bore to bypass junk in the hole is not classified as a side-track. Quite a number of wells in the Gulf of Mexico are completed in producing intervals at subsea depths between 1000 feet and 10 000 feet. In areas where the geology and formation pressures have previously been established, such development wells are routinely drilled in from 1 to 10 days, due to the unconsolidated nature of the formations at depths above 10 000 feet.

It should further, be noted that the drilling period for many of the US GoM wells is of very short duration. If looking at all the wells (1980 – 2002); • Approximately 25 % of the development wells were drilled in less than 10 days. • Approximately 19 % of the exploration wells were drilled in less than 10 days.

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5.1.2 United Kingdom The drilling exposure data for UK is based on "The Energy Report, Volume 2, Oil and Gas Resources of the United Kingdom", Department of Trade and Industry 1994 – 2001, and Department of Trade and industry web page (http://www.og.dti.gov.uk/information) for the past years. The number of wells drilled in the UK area is presented in Table 5.2. Table 5.2 Number of drilled wells in UK offshore sector

Exploration wells Wild cat Appraisal

Development wells Year

All wells inc. sidetracks

Sidetrack-ed wells

All wells inc. sidetracks

Sidetrack-ed wells

Total All wells inc. sidetracks

Sidetrack-ed wells

1980 32 22 54 122 1981 48 26 74 137 1982 68 43 111 118 1983 77 51 128 95 1984 106 76 182 108 1985 93 64 157 133 1986 73 40 113 85 1987 69 63 132 124 1988 93 3 84 14 177 167 6 1989 94 2 89 14 183 155 12 1990 159 7 65 11 224 124 16 1991 107 1 79 19 186 144 19 1992 74 2 57 16 131 167 27 1993 51 1 59 12 110 162 28 1994 62 3 37 10 99 202 48 1995 60 7 38 12 98 244 42 1996 72 3 40 7 112 261 68 1997 61 2 35 12 96 257 78 1998 47 4 33 17 80 276 89 1999 16 2 20 3 36 230 90 2000 26 3 33 11 59 216 81 2001 24 2 36 18 60 282 106 2002 16 2 28 10 44 249 122 2003 26 2 19 9 45 204 79 2004 29 3 34 12 63 166 68

Total 1583 49 1171 207 2754 4428 979

5.1.3 Norway The drilling exposure data for Norway is based on the NPD Borehole list as published on the Internet (http://www.npd.no). NPD has from 2001 changed the well naming. This is also reflected in their borehole lists published on the Internet. The tables presenting number of drilled wells in earlier versions of this report have been based on the number of wellbores. A wellbore is now categorized as;

• Initial well bore • Re-entry • Sidetrack

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Earlier another category named technical sidetrack also was included. This category is not used anymore. The practical effect is that the number of wells drilled has been reduced. NPD wellbore categorizing is described (http://www.npd.no/regelverk/r2002/B_og_b_betegnelser_og_klassifisering_e.htm)

The number and type of development wells are presented in Table 5.3. Table 5.4 presents the exploration wells drilled in the Norwegian area alongside the total number of development wells and the type of well bore. Table 5.5 shows the number of Norwegian wells drilled within each main NCS area Table 5.3 Norwegian development wells drilled

Production Injection Spud year Oil Gas Oil/-

gas

Gas/-conden

sate

Other/-un-

knownTotal Water Gas Water/-

gas

Other/-un-

knownTotal

Obser-vation

All wells

1980 20 6 26 2 2 281981 8 5 13 1 2 3 161982 12 6 18 3 2 5 231983 14 1 15 6 3 9 241984 16 10 26 7 1 8 341985 25 11 36 10 2 12 481986 37 4 41 7 2 9 501987 25 13 38 9 1 10 481988 38 4 42 12 1 13 551989 44 3 47 16 3 19 661990 35 4 39 19 2 21 601991 48 2 50 12 1 13 1 641992 55 7 62 15 1 16 8 861993 68 7 1 76 15 3 18 11 1051994 70 6 2 78 25 4 29 13 1201995 58 11 3 72 19 3 1 23 14 1091996 84 20 3 107 9 6 1 16 20 1431997 72 19 1 92 5 10 1 1 17 26 1351998 87 10 97 14 8 1 23 19 1391999 89 8 1 98 17 3 6 26 25 1492000 111 15 2 3 131 14 10 1 25 29 1852001 123 13 2 138 15 4 2 2 23 39 2002002 105 9 2 116 15 6 2 2 25 26 1672003 111 7 2 2 122 12 2 6 5 25 18 1652004 96 4 1 6 1 108 10 4 14 16 138

Total 1451 203 4 8 22 1688 287 82 19 16 404 265 2357

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Table 5.4 Number of drilled wells and type of well bore in Norwegian offshore sector Exploration wells Development

Appraisal Wildcat Drilled year

Initial Re-entry

Side-track

Total Initial Re-entry

Side-track

TotalTotal

explor-ation

Initial Multi-lateral

Side-track

Total develop-

ment 1980 10 1 11 26 5 31 42 27 1 281981 15 1 16 24 3 27 43 16 161982 13 1 1 15 35 2 37 52 21 2 231983 8 2 10 32 32 42 21 3 241984 13 2 15 33 4 1 38 53 31 3 341985 20 1 21 30 2 32 53 47 1 481986 10 2 1 13 24 5 1 30 43 35 15 501987 11 3 1 15 24 3 27 42 36 12 481988 8 2 3 13 18 18 31 46 9 551989 5 4 2 11 21 3 24 35 47 19 661990 8 4 2 14 26 6 32 46 43 17 601991 11 7 2 20 33 3 1 37 57 52 12 641992 10 5 15 27 2 1 30 45 65 21 861993 7 4 11 19 4 1 24 35 75 30 1051994 2 3 1 6 17 3 1 21 27 78 1 41 1201995 10 1 4 15 22 3 25 40 73 36 1091996 7 1 2 10 21 1 22 32 91 52 1431997 8 1 4 13 33 4 5 42 55 81 1 53 1351998 6 3 2 11 15 3 18 29 90 3 46 1391999 6 1 1 8 12 1 3 16 24 95 54 1492000 4 2 6 18 3 21 27 107 6 72 1852001 5 2 4 11 24 3 1 28 39 93 18 89 2002002 2 2 3 7 11 1 3 15 22 73 18 76 1672003 6 2 2 10 12 2 2 16 26 59 32 74 1652004 4 4 8 10 10 18 60 28 50 138Total 209 50 46 305 567 63 23 653 958 1462 107 788 2357

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Table 5.5 Norwegian drilled wells separated on main NCS area Exploration wells Development wells Spud

year Barents Sea

North Sea

Norwegian Sea Total Barents

Sea NorthSea

Norwegian Sea Total

Total all wells

1980 2 39 1 42 28 28 701981 3 38 2 43 16 16 591982 4 43 5 52 23 23 751983 6 29 7 42 24 24 661984 10 36 7 53 34 34 871985 8 29 16 53 48 48 1011986 4 22 17 43 50 50 931987 5 23 14 42 48 48 901988 4 21 6 31 55 55 861989 5 27 3 35 66 66 1011990 3 33 10 46 60 60 1061991 3 46 8 57 64 64 1211992 3 37 5 45 84 2 86 1311993 2 25 8 35 94 11 105 1401994 22 5 27 107 13 120 1471995 1 31 8 40 104 5 109 1491996 24 8 32 131 12 143 1751997 36 19 55 118 17 135 1901998 22 7 29 113 26 139 1681999 13 11 24 117 32 149 1732000 4 12 11 27 154 31 185 2122001 4 21 14 39 167 33 200 2392002 17 5 22 149 18 167 1892003 20 6 26 145 20 165 1912004 12 6 18 1 115 22 138 156Total 71 678 209 958 1 2114 242 2357 3315

5.1.4 The Netherlands The drilling exposure data for The Netherlands is based on information from the Dutch Ministry of Economic Affairs. The information is available on Internet: (http://www.nitg.tno.nl). The number of wells drilled in the Dutch Continental Shelf is presented in Table 5.6.

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Table 5.6 Number of drilled wells on the Dutch Continental Shelf Exploration wells YEAR

Exploration Appraisal Total Development

wells Total all

wells 1980 26 5 31 7 38 1981 15 17 32 5 37 1982 35 10 45 20 65 1983 31 12 43 15 58 1984 26 7 33 24 57 1985 36 7 43 35 78 1986 25 5 30 15 45 1987 22 5 27 13 40 1988 21 5 26 21 47 1989 23 5 28 17 45 1990 29 6 35 14 49 1991 43 2 45 18 63 1992 19 1 20 15 35 1993 13 1 14 17 31 1994 10 2 12 10 22 1995 5 3 8 16 24 1996 24 5 29 6 35 1997 21 10 31 13 44 1998 17 3 20 13 33 1999 12 2 14 6 20 2000 6 6 12 9 21 2001 15 4 19 12 31 2002 16 3 19 13 32 2003 7 4 11 13 24 2004 11 2 13 6 19

Total 508 132 640 353 993

5.1.5 Canadian East Coast Table 5.7 shows the number of wells drilled on the Canadian East Coast. Before 1980 approximately 225 wells were drilled. (http://www.gsca.nrcan.gc.ca/BASIN/DEMO/basin-f.cgi). There has in addition been drilled approximately 160 well in the Northern areas all time. No detailed data has, however, been made available from this area. Some drilling activity is also carried out on the West Coast of Canada.

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Table 5.7 Number of drilled wells on the Canadian East Coast Exploration Development Year

Explora-tory

Deli-neation

Total exploration

Devel-opment

Gas injector

Water injector

Cutting injector

Service & relief

Total devel-opment

Total

1980 12 6 18 181981 13 5 18 181982 19 2 21 211983 20 5 25 251984 25 5 30 1 1 311985 23 15 38 1 1 391986 13 5 18 181987 4 6 10 101988 9 5 14 141989 2 2 21990 1 1 11991 4 4 4 1 5 91992 7 7 71993 11 11 111994 1 1 6 6 71995 1 1 3 3 41996 2 2 3 3 51997 4 4 6 6 101998 1 1 2 20 5 3 28 301999 6 4 10 26 6 4 1 37 472000 9 5 14 33 1 4 38 522001 9 5 14 13 2 5 20 342002 7 5 12 21 2 10 33 452003 7 2 9 20 1 7 28 372004 2 1 3 18 4 10 32 35Total 194 77 271 191 21 43 2 2 259 530

5.1.6 US Pacific OCS Table 5.8 shows the number of wells drilled on the in the US Pacific OCS area. The data stems from MMS pacific division. Table 5.8 Number of drilled wells in the US Pacific OCS area

Year Expl. wells spudded Dev. wells spudded Total 1980 10 40 50 1981 14 50 64 1982 27 58 85 1983 38 44 82 1984 19 45 64 1985 6 39 45 1986 5 34 39 1987 4 39 43 1988 3 29 32 1989 4 15 19 1990 17 17 1991 8 8 1992 5 5 1993 21 21 1994 25 25 1995 19 19 1996 31 31 1997 29 29 1998 19 19 1999 11 11 2000 13 13 2001 16 16 2002 21 21 2003 18 18 2004 20 20 Total 130 666 796

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5.1.7 Australia Table 5.9 shows the number of wells drilled on the in Australian waters. The data stems from Geoscience Australia. Geoscience Australia is the national agency for geoscience research and geospatial information. Table 5.9 Number of drilled wells in Australian waters

Exploration Wildcat Appraisal

Development Year

Original hole

Side track Total Original

hole Side track Total Total Original

hole Side track Total

Total all wells

1980 15 3 18 2 2 20 6 1 7 271981 13 13 5 5 18 16 16 341982 42 5 47 4 4 51 12 12 631983 41 3 44 4 4 48 29 29 771984 29 3 32 12 12 44 42 1 43 871985 23 23 18 18 41 18 18 591986 20 20 7 7 27 19 19 461987 9 1 10 6 6 16 21 21 371988 27 5 32 9 1 10 42 13 13 551989 32 10 42 10 4 14 56 26 1 27 831990 46 8 54 19 6 25 79 18 6 24 1031991 34 5 39 6 4 10 49 17 5 22 711992 28 3 31 13 2 15 46 14 1 15 611993 36 1 37 14 3 17 54 18 3 21 751994 28 6 34 20 1 21 55 28 6 34 891995 32 2 34 23 2 25 59 32 8 40 991996 34 9 43 15 15 58 34 4 38 961997 39 1 40 19 2 21 61 81 14 95 1561998 61 5 66 10 1 11 77 41 8 49 1261999 45 5 50 9 9 59 35 3 38 972000 60 10 70 4 4 74 22 3 25 992001 48 3 51 10 10 61 24 7 31 922002 31 4 35 16 3 19 54 26 8 34 882003 44 5 49 16 16 65 32 12 44 1092004 36 36 14 4 18 54 41 7 48 102Total 853 97 950 285 33 318 1268 665 98 763 2031

5.1.8 Denmark Table 5.10 shows the number of wells drilled on the offshore Denmark. The data stems from The Danish Energy Authority.

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Table 5.10 Number of drilled wells offshore Denmark

Year Exploration and appraisal Development Sum

1980 1 7 8 1981 4 9 13 1982 5 18 23 1983 14 13 27 1984 8 15 23 1985 14 18 32 1986 7 3 10 1987 8 3 11 1988 3 13 16 1989 4 9 13 1990 2 15 17 1991 6 14 20 1992 11 15 26 1993 2 30 32 1994 2 15 17 1995 1 16 17 1996 4 13 17 1997 8 15 23 1998 6 23 29 1999 9 17 26 2000 12 17 29 2001 15 29 44 2002 9 27 36 2003 8 24 32 2004 10 23 33 Total 173 401 574

5.1.9 Compiled Drilling Exposure Data Table 5.11 below is based on Table 5.1 to Table 5.4, and shows compiled offshore drilled wells in Norway, UK and US GoM OCS. Table 5.12 is based on Table 5.6 to Table 5.10 and shows compiled offshore drilled wells in the Netherlands, Canada East Coast, Australia, US Pacific OCS, and Denmark.

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Table 5.11 An overview of offshore drilled wells in Norway, UK, and US GoM OCS Year Expl. US

GoM OCSDev. US

GoM OCSExpl. UK Dev. UK Expl.

Norway Dev.

Norway Expl. Total Dev. Total

1980 361 807 54 122 42 28 457 9571981 337 870 74 137 43 16 454 10231982 392 838 111 118 52 23 555 9791983 381 762 128 95 42 24 551 8811984 556 755 182 108 53 34 791 8971985 511 662 157 133 53 48 721 8431986 255 433 113 85 43 50 411 5681987 396 448 132 124 42 48 570 6201988 532 452 177 167 31 55 740 6741989 455 511 183 155 35 66 673 7321990 490 566 224 124 46 60 760 7501991 330 430 186 144 57 64 573 6381992 215 329 131 167 45 86 391 5821993 345 570 110 162 35 105 490 8371994 417 589 99 202 27 120 543 9111995 376 675 98 244 40 109 514 10281996 439 697 112 261 32 143 583 11011997 521 837 96 257 55 135 672 12291998 496 641 80 276 29 139 605 10561999 370 662 36 230 24 149 430 10412000 440 937 59 216 27 185 526 13382001 411 852 60 282 39 200 510 13342002 308 633 44 249 22 167 374 10492003 354 539 45 204 26 165 425 9082004 362 553 63 166 18 138 443 857Total 10050 16048 2754 4428 958 2357 13762 22833

Table 5.12 An overview of offshore drilled wells in Canada East Coast, the Netherlands, Australia, US Pacific OCS, and Denmark

Year Expl. Dutch

Dev. Dutch

Expl. Canada E. Coast

Dev. Canada E. Coast

Expl. Aust-ralia

Dev. Aust-ralia

Expl. US Pacific OCS

Dev. US Pacific OCS

Expl. Den-mark

Dev. Den-mark

Expl. total

Dev. total

1980 31 7 18 20 7 10 40 1 7 80 611981 32 5 18 18 16 14 50 4 9 86 801982 45 20 21 51 12 27 58 5 18 149 1081983 43 15 25 48 29 38 44 14 13 168 1011984 33 24 30 1 44 43 19 45 8 15 134 1281985 43 35 38 1 41 18 6 39 14 18 142 1111986 30 15 18 27 19 5 34 7 3 87 711987 27 13 10 16 21 4 39 8 3 65 761988 26 21 14 42 13 3 29 3 13 88 761989 28 17 2 56 27 4 15 4 9 94 681990 35 14 1 79 24 17 2 15 117 701991 45 18 4 5 49 22 8 6 14 104 671992 20 15 7 46 15 5 11 15 77 571993 14 17 11 54 21 21 2 30 70 1001994 12 10 1 6 55 34 25 2 15 70 901995 8 16 1 3 59 40 19 1 16 69 941996 29 6 2 3 58 38 31 4 13 93 911997 31 13 4 6 61 95 29 8 15 104 1581998 20 13 2 28 77 49 19 6 23 105 1321999 14 6 10 37 59 38 11 9 17 92 1092000 12 9 14 38 74 25 13 12 17 112 1022001 19 12 14 20 61 31 16 15 29 109 1082002 19 13 12 33 54 34 21 9 27 94 1282003 11 13 9 28 65 44 18 8 24 93 1272004 13 6 3 32 54 48 20 10 23 80 129Total 640 353 271 259 1268 763 130 666 173 401 2482 2442

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5.2 Production Exposure Data

5.2.1 US GoM OCS The production exposure data for US GoM OCS is shown in Table 5.13. The data is based on MMS Ogor A files from 1986 – 2006 (/1/). These files list the well individual activity for each month. It was selected to use the data from December each year. All the production wells listed with production in December are counted as active wells. Table 5.13 Producers in the US GoM OCS area.

Oil production Year Flowing Gas lift Total

Gas production

Total production

Water injection (active or inactive)

Gas injection (active or inactive)

1980 NA NA 3165 3023 6188 107 1981 NA NA 3260 3106 6366 121 1982 NA NA 3412 3223 6635 143 1983 NA NA 3539 3243 6782 187 1984 NA NA 3688 3355 7043 219 1985 2695 1101 3796 3229 7025 327 100 1986 2523 1206 3729 3239 6968 327 88 1987 2461 1284 3745 3311 7056 320 105 1988 2382 1361 3743 3364 7107 327 100 1989 2230 1270 3500 3429 6929 311 91 1990 2283 1246 3529 3682 7211 320 89 1991 2206 1339 3545 3580 7125 323 80 1992 2195 1311 3506 3346 6852 325 80 1993 2216 1326 3542 3458 7000 315 72 1994 2228 1286 3514 3483 6997 307 72 1995 2189 1258 3447 3430 6877 305 70 1996 2016 1424 3440 3444 6884 294 61 1997 2002 1434 3436 3467 6903 270 52 1998 1936 1364 3300 3315 6615 261 51 1999 1712 1538 3250 3282 6532 248 50 2000 1723 1590 3313 3308 6621 246 45 2001 1523 1716 3239 3217 6456 225 34 2002 1327 1782 3109 2993 6102 207 27 2003 1160 1926 3086 3043 6129 205 30 2004 1060 1539 2599 2804 5403 199 35

Total - - 85432 82374 167806 6439 1332

5.2.2 United Kingdom The production/injection exposure data for UK is shown in Table 5.14. The figures are valid for the number of wells that have been in service for the listed year. The data from before 1991 is based on well data systematically collected in the SINTEF study "Reliability of Well Completion Equipment" SINTEF report STF 75 F92019, "Development of the Oil and Gas resources of the United Kingdom" 1980, 1992 and 1993 edition, North Sea Field Development Guide, 4th edition, OPL and coarse assumptions where well data are missing. The data is therefore not exactly correct. The data from 1991 to 1999 is based on statistics from Health & Safety Executive (HSE). HSE has now stopped reporting this information on an individual well basis. They now report the production data for each field. Deal Data Registry for UK Offshore Oil & Gas (http://www.ukdeal.co.uk/) reports individual well information, but the quality of information is variable, and the data cannot be used. The department of Energy was contact in October 2004, but is no longer collected by the

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Department and has not in fact been collected since 1999. All they could suggest was that the oil companies that operate the field or well could be approached and requested for data. This will be a too time-consuming task. The exposure data for 2000 - 2003 has therefore been estimated.

Table 5.14 Producers and injectors in the UK waters Production wells Injection wells Year

Oil Gas/con Total Gas Water Total Total wells

1980 291 249 540 10 92 102 642 1981 318 252 570 11 104 115 685 1982 349 256 605 13 116 129 734 1983 399 258 657 17 140 157 814 1984 448 266 714 22 170 192 906 1985 456 298 754 21 194 215 969 1986 525 322 847 27 206 233 1080 1987 558 355 913 29 218 247 1160 1988 550 390 940 35 217 252 1192 1989 575 419 994 35 227 262 1256 1990 599 474 1073 37 249 286 1359 1991 844 344 1188 68 350 418 1606 1992 918 502 1420 68 363 431 1851 1993 968 549 1517 66 369 435 1952 1994 1041 598 1639 62 399 461 2100 1995 1131 703 1834 60 413 473 2307 1996 1215 695 1910 69 428 497 2407 1997 1252 725 1977 68 434 502 2479 1998 1160 713 1873 58 369 427 2300 1999 1118 678 1796 37 345 382 2178 2000* 1027 726 1753 37 345 382 2135 2001* 953 714 1667 37 345 382 2049 2002* 943 696 1639 37 345 382 2021 2003* 867 685 1552 37 345 382 1934 2004* 777 640 1417 37 345 382 1799 Total 19282 12507 31789 998 7128 8126 39915

* Data are no longer available from HSE. The number of wells in production has been assumed to be relative to the UK annual oil and gas production. Injection wells remain unchanged.

5.2.3 Norway Table 5.15 shows the production/injection exposure data for the Norwegian waters. The figures are valid for the number of wells in service per December 31 the listed year. The data is from the NPD Annual reports 1980 – 1999, and for the year 1999 and later the data stems from the NPD Borehole list as published on the Internet (http://www.npd.no).

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Table 5.15 Production/injection exposure data for the Norwegian waters Producers Year

Oil Cond Gas Other/-unknown

Total Injection/-

observationSuspended/-

closed in/plugged

Total

1980 84 29 47 160 8 23 1911981 89 34 48 171 11 26 2081982 114 35 47 196 13 24 2331983 113 32 53 198 17 37 2521984 128 31 61 220 23 42 2851985 145 29 61 235 32 60 3271986 160 38 64 262 41 71 3741987 176 41 60 277 41 102 4201988 201 43 65 309 59 110 4781989 235 38 48 321 74 151 5461990 258 33 31 322 88 191 6011991 285 31 33 349 109 207 6651992 324 29 30 383 116 247 7461993 371 31 32 434 136 280 8501994 385 32 34 451 163 357 9711995 434 35 24 493 180 409 10821996 494 33 53 580 189 459 12281997 519 31 62 612 194 544 13501998 535 25 64 624 211 649 14841999 746 25 83 854 259 549 16622000 787 25 85 897 259 701 18572001 813 21 95 929 266 833 20282002 820 32 101 953 257 1030 22402003 849 30 97 976 261 1111 23482004 848 32 97 7 984 264 1244 2492Total 9913 795 1475 7 12190 3271 9457 24918

Note! NPD stopped listing the number of wells in production in the annual reports in 1999. From 1999 the no. of oil producers seems high, and the no. of closed in/suspended wells seems low, compared to the earlier years.

5.2.4 US Pacific OCS The production exposure data for US Pacific OCS is shown in Table 5.16. The data is based on MMS Ogor A files (/1/). These files list the well individual activity for each month. It was selected to use the data from December each year. All the production wells listed with production in December are counted as active wells.

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Table 5.16 Producers in the US Pacific OCS area. Oil production Year

Flowing Gas lift Total Gas

productionTotal

productionWater injection

(active or inactive)Gas injection

(active or inactive)1986 262 79 341 20 361 79 6 1987 280 81 361 20 381 84 6 1988 284 83 367 16 383 88 4 1989 293 79 372 13 385 83 4 1990 305 72 377 19 396 83 4 1991 321 65 386 20 406 84 5 1992 340 49 389 19 408 84 4 1993 337 54 391 20 411 88 4 1994 322 79 401 17 418 93 4 1995 300 104 404 17 421 94 6 1996 287 118 405 13 418 84 7 1997 289 107 396 17 413 87 9 1998 285 100 385 19 404 93 13 1999 264 100 364 18 382 93 14 2000 264 103 367 16 383 83 15 2001 255 105 360 17 377 74 11 2002 257 120 377 16 393 97 11 2003 256 122 378 15 393 98 12 2004 251 121 372 15 387 100 14 Total 5452 1741 7193 327 7520 1669 153

5.2.5 Compiled Production Exposure Data Table 5.17 is based on Table 5.13, Table 5.14 and Table 5.15, and shows overall production data for the Norway, UK and US GoM OCS. The figures are valid for number of wells in service per December the listed year. Note that it has been selected not to included data from the US Pacific OCS. Table 5.17 Overall production data for the US GoM OCS, UK, and Norway based on Table 5.13,

Table 5.14 and Table 5.15. US GoM OCS United Kingdom Norway Total

Production wells Production wells Production wells Production wells Year

Oil Gas/-cond

Total Inject-

ion wells

Oil Gas/- cond

Total Inject-

ion wells

Oil Gas/-cond

Total Inje-ction wells

Oil Gas/-cond

Total Inject-

ion wells

1980 3165 3023 6188 107 291 249 540 102 84 76 160 8 3540 3348 6888 2171981 3260 3106 6366 121 318 252 570 115 89 82 171 11 3667 3440 7107 2471982 3412 3223 6635 143 349 256 605 129 114 82 196 13 3875 3561 7436 2851983 3539 3243 6782 187 399 258 657 157 113 85 198 17 4051 3586 7637 3611984 3688 3355 7043 219 448 266 714 192 128 92 220 23 4264 3713 7977 4341985 3796 3229 7025 427 456 298 754 215 145 90 235 32 4397 3617 8014 6741986 3729 3239 6968 415 525 322 847 233 160 102 262 41 4414 3663 8077 6891987 3745 3311 7056 425 558 355 913 247 176 101 277 41 4479 3767 8246 7131988 3743 3364 7107 427 550 390 940 252 201 108 309 59 4494 3862 8356 7381989 3500 3429 6929 402 575 419 994 262 235 86 321 74 4310 3934 8244 7381990 3529 3682 7211 409 599 474 1073 286 258 64 322 88 4386 4220 8606 7831991 3545 3580 7125 403 844 344 1188 418 285 64 349 109 4674 3988 8662 9301992 3506 3346 6852 405 918 502 1420 431 324 59 383 116 4748 3907 8655 9521993 3542 3458 7000 387 968 549 1517 435 371 63 434 136 4881 4070 8951 9581994 3514 3483 6997 379 1041 598 1639 461 385 66 451 163 4940 4147 9087 10031995 3447 3430 6877 375 1131 703 1834 473 434 59 493 180 5012 4192 9204 10281996 3440 3444 6884 355 1215 695 1910 497 494 86 580 189 5149 4225 9374 10411997 3436 3467 6903 322 1252 725 1977 502 519 93 612 194 5207 4285 9492 10181998 3300 3315 6615 312 1160 713 1873 427 535 89 624 211 4995 4117 9112 9501999 3250 3282 6532 298 1118 678 1796 382 746 108 854 259 5114 4068 9182 9392000 3313 3308 6621 291 1027 726 1753 382 787 110 897 259 5127 4144 9271 9322001 3239 3217 6456 259 953 714 1667 382 813 116 929 266 5005 4047 9052 9072002 3109 2993 6102 234 943 696 1639 382 820 133 953 257 4872 3822 8694 8732003 3086 3043 6129 235 867 685 1552 382 849 127 976 261 4802 3855 8657 8782004 2599 2804 5403 234 777 640 1417 382 848 136 984 264 4224 3580 7804 880Total 85432 82374 167806 7771 19282 12507 31789 8126 9913 1634 11547 3271 114627 96515 211142 19168

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6. Various Exposure Data

This section includes various exposure data. It should be noted that this exposure data does not include information from the complete period 1980 – 1999. Limitations related to the exposure data are explained where the data is presented. The exposure data presented in this section covers the following:

1. Well Depth Related Exposure Data

• US GoM OCS Wells • Norwegian Wells

2. Water depth related drilling exposure data • US GoM OCS Wells • UK Wells • Norwegian Wells

3. Shut-in Wellhead Pressure Related exposure data • US GoM OCS Drilling Wells • Norwegian Drilling Wells • US Wells in Production

4. Gas Oil Ratio Related Exposure Data 5. Workover Frequency Exposure Data 6. Wireline Frequency Exposure Data 7. Coiled Tubing and Snubbing Exposure Data

Data from the US Mineral Management Service (MMS) and NPD has formed the main input to this section.

6.1 Well Depth Related Exposure Data

6.1.1 US GoM OCS Wells The information in this sub-section stems from the MMS Borehole file (/1/). The drilling vertical depths for the exploration and development wells in the US GoM OCS are presented in Figure 6.1 and Figure 6.2. Approximately 0.8 % of the exploration wells and 1.3% of the development wells were not listed with a True Vertical Depth (TVD). These wells are not included in Figure 6.1 and Figure 6.2.

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Exploration wells, US GoM OCS (1980 - 2004)

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Percentage distribution

TVD

(met

er)

Figure 6.1 All exploration wells drilled in 1980 – 2004 listed with true vertical depth

Development wells, US GoM OCS (1980 - 2004)

0

2000

4000

6000

8000

10000

12000

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%Percentage distribution

TVD

(met

er)

Figure 6.2 All development wells drilled in 1980 – 2004 listed with true vertical depth

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6.1.2 Norwegian Wells For Norwegian wells True Vertical Depth (TVD) of wells is not available for neither exploration nor development wells drilled before 1995. Measured Depths (MD) is, however, available. For most exploration wells the MD is a good approximation for the TVD. For development wells the MD will not be a good approximation. Figure 6.3 shows the true vertical depth for production wells drilled in the period 1995 – mid 1998. Figure 6.4 shows the measured depth for development wells drilled in the period 1980 – 2004. Figure 6.5 shows the measured depth for exploration wells drilled in the period 1980 - 2004. The data shown in Figure 6.3 stems from the NPD Daily Drilling Report system, Figure 6.4 and Figure 6.5 stems from the NPD well files as published on the Internet.

True vertical depth, production wells,(mainly drilled in 95 - mid 98)

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Percentage distribution (total 478 wells)

TVD

(mR

KB

)

Figure 6.3 True Vertical Depth, Norwegian production wells

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Development wells, Norwegian waters (1980 - 2004)

0

2000

4000

6000

8000

10000

12000

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Percentage distribution

Mea

sure

dde

pth

(m)

Figure 6.4 Measured depth for development wells 1980 – 2004

Exploration wells, Norwegian waters (1980 - 2004)

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Percentage distribution

Mea

sure

dde

pth

Figure 6.5 Measured depth, Norwegian exploration wells 1980 – 2004.

6.2 Water Depth Related Drilling Exposure Data

The past years some deepwater blowouts have occurred. This section presents the water depth related drilling exposure data. Table 6.1 and Table 6.2 present the water depth specific no. of exploration and development wells drilled in the US GoM OCS.

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Table 6.1 Exploration wells drilled in the US GoM OCS vs. water depth (/1/) Number of wells drilled within water depth range (m)

Spud year<50 50 –

100 100 – 200

200 – 400

400 – 600

600- 1000

1000 –1500

1500-2000

2000- 2500 >2500 Un-

known Total

1980 206 121 17 10 2 1 4 3611981 190 101 25 9 8 4 3371982 264 87 18 8 5 10 3921983 248 79 28 16 7 1 2 3811984 318 126 36 29 23 13 1 10 5561985 249 111 56 44 23 22 6 5111986 124 54 32 17 15 13 2551987 212 92 45 16 10 11 4 2 2 2 3961988 288 99 57 27 23 23 4 1 2 8 5321989 238 100 46 16 19 23 4 1 8 4551990 261 107 49 15 13 31 8 2 1 3 4901991 168 90 24 19 4 15 6 1 3 3301992 99 87 13 8 2 2 1 3 2151993 180 91 37 10 11 6 2 8 3451994 225 105 25 13 5 27 9 2 6 4171995 179 97 31 17 14 21 8 2 7 3761996 207 107 28 20 9 29 25 5 2 7 4391997 229 117 39 27 20 24 51 5 4 5 5211998 228 120 23 16 30 33 35 8 1 2 4961999 148 97 18 7 14 27 25 26 7 1 3702000 215 90 18 9 12 35 34 9 16 2 4402001 165 58 26 18 7 39 55 24 16 3 4112002 148 48 8 7 12 23 25 17 17 3 3082003 176 62 17 9 8 19 29 21 6 7 3542004 173 45 18 19 8 22 27 21 17 12 362Total 5138 2291 734 406 304 459 353 147 92 27 99 10050

Table 6.2 Development wells drilled in the US GoM OCS vs. water depth (/1/) Number of wells drilled within water depth range (m)

Spud year<50 50 –

100 100 – 200

200 – 400

400 – 600

600- 1000

1000 –1500

1500-2000

2000- 2500 >2500 Un-

known Total

1980 363 327 60 37 20 8071981 480 274 73 29 14 8701982 451 293 62 19 13 8381983 447 226 56 21 12 7621984 434 234 54 19 14 7551985 302 255 53 33 2 17 6621986 173 169 50 32 1 8 4331987 247 117 41 34 3 1 5 4481988 206 142 53 29 14 2 6 4521989 237 153 57 44 14 2 4 5111990 254 165 97 24 19 1 6 5661991 181 132 87 11 7 3 9 4301992 172 82 28 34 1 8 4 3291993 293 187 41 35 4 1 9 5701994 294 198 37 28 5 2 1 24 5891995 327 221 55 25 15 5 1 26 6751996 338 220 70 33 7 19 10 6971997 408 278 61 23 26 24 4 1 2 10 8371998 322 181 62 34 11 11 16 1 1 2 6411999 300 219 43 29 11 27 24 5 1 3 6622000 446 300 49 41 8 21 60 9 2 1 9372001 418 225 69 35 17 23 36 23 6 8522002 303 146 21 34 9 24 76 11 9 6332003 306 91 33 20 8 18 48 12 1 2 5392004 329 105 33 15 8 15 13 16 19 553Total 8031 4940 1345 718 189 206 278 81 41 2 217 16048

Table 6.3 and Table 6.4 present the water depth specific no. of exploration and development wells drilled in Norwegian waters.

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Table 6.3 Exploration wells drilled in UK waters vs. water depth (http://www.ukdeal.co.uk/)Number of wells drilled within water depth range (m)*

Spud year < 50 50 –

100 100 – 200

200 – 400

400 – 600

600 – 1000

1000 - 1500

1500 - 2000

Total

1980 15 49 2 1 3 1 711981 2 30 58 2 2 941982 23 44 65 2 1 1351983 34 42 76 2 1541984 47 73 89 4 5 2181985 43 45 81 4 6 1791986 29 40 62 2 1331987 43 39 69 2 1531988 58 46 86 2 1921989 58 44 96 2 2001990 60 53 130 2 3 2481991 49 60 102 1 3 2151992 29 47 68 1 5 1501993 31 35 51 6 1231994 39 26 27 3 11 1 1071995 32 32 30 5 7 3 1091996 29 34 48 3 2 3 1 1201997 22 23 53 1 5 1 1051998 15 23 39 3 2 821999 9 11 20 1 1 1 432000 9 12 31 1 3 2 1 592001 9 22 34 1 1 2 692002 10 16 20 1 1 2 502003 12 18 13 3 2 482004 11 16 38 3 1 3 72Total 703 846 1435 44 63 24 12 2 3129

* Note that the numbers of wells are 12% higher than in Table 5.2, page 41 because different sources of information have been used.

Table 6.4 Development wells drilled in UK waters vs. water depth (http://www.ukdeal.co.uk/)

Number of wells drilled within water depth range (m)* Spud year

< 50 50 – 100

100 – 200

200 – 400

400 – 600

600 – 1000

1000 - 1500

1500 - 2000

Total

1980 9 11 129 1491981 12 10 127 1491982 14 18 105 1371983 15 14 75 1041984 26 15 81 2 1241985 39 16 93 2 1501986 35 3 60 981987 41 20 82 1431988 56 32 87 1751989 58 14 83 1 1 1571990 41 14 67 2 1 1251991 47 37 68 1 1531992 58 31 81 5 1751993 35 26 108 3 1721994 58 36 110 1 2 2071995 91 37 134 3 2651996 29 67 175 5 11 2871997 26 53 170 9 4 2621998 37 64 173 12 7 2931999 42 51 130 1 12 2362000 35 36 148 5 5 2292001 34 39 203 5 12 2932002 42 47 151 5 13 2 2 2622003 39 43 110 3 8 2 2052004 15 33 106 10 3 167Total 934 767 2856 69 83 6 2 4717

* Note that the numbers of wells are 6% higher than in Table 5.2, page 41 because different sources of information have been used.

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Table 6.5 and Table 6.6 present the water depth specific no. of exploration and development wells drilled in Norwegian waters. Table 6.5 Exploration wells drilled in Norwegian waters vs. water depth

Number of wells drilled within water depth range (m) Spud year

<50 50 – 100

100 – 200

200 – 400

400 – 600

600- 1000

1000 – 1500

1500 – 2000

Total

1980 9 13 20 421981 8 22 13 431982 18 19 15 521983 6 14 22 421984 12 12 29 531985 3 16 34 531986 5 13 24 1 431987 4 16 19 3 421988 9 7 13 2 311989 11 14 9 1 351990 19 12 15 461991 21 13 22 1 571992 10 11 23 1 451993 10 11 14 351994 1 4 12 10 271995 6 25 9 401996 7 5 19 1 321997 13 19 19 1 1 2 551998 4 11 11 3 291999 3 5 15 1 242000 1 7 16 2 1 272001 1 16 19 2 1 392002 2 10 7 1 1 1 222003 6 11 7 2 262004 1 8 9 18Total 1 193 322 413 16 5 7 1 958

Table 6.6 Development wells drilled in Norwegian waters vs. water depth Number of wells drilled within water depth range (m) Spud year

50 - 100 100 - 200 200 - 400 400 - 600 Total

1980 21 7 28 1981 10 6 16 1982 5 18 23 1983 9 15 24 1984 13 21 34 1985 12 36 48 1986 25 25 50 1987 25 23 48 1988 35 20 55 1989 34 29 3 66 1990 27 25 8 60 1991 31 23 10 64 1992 25 50 11 86 1993 31 48 26 105 1994 38 40 42 120 1995 26 43 40 109 1996 26 61 56 143 1997 29 42 64 135 1998 28 47 64 139 1999 16 60 72 1 149 2000 18 79 88 185 2001 26 89 85 200 2002 26 73 67 1 167 2003 30 66 69 165 2004 31 51 56 138 Total 597 997 761 2 2357

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6.3 Shut-in Wellhead Pressure Related Exposure Data

All data for the US GoM OCS wells stems from (/1/). Only data for wells that are completed as producers are included. For the Norwegian wells the main source of information has been a list of HPHT wells from NPD combined with the NPD Borehole list. For the UK wells no pressure related data is presented.

6.3.1 US GoM OCS Drilling Wells The shut-in wellhead pressure exposure data for drilling wells (both development and exploration wells) are all based on the first production well test carried out on the well. In US GoM OCS many exploration wells are completed as producers (see Table 5.1). It should also be noted that many development wells are not completed as producers, because they are dry. Since the shut-in wellhead pressures have been recorded more frequent the last 5 to 10 years than the previous years it was selected to only include data from wells that have been spudded after January 1988 Development drilling There were in total 1417 development wells listed with a shut-in wellhead pressure on the first well test after completion. In Figure 6.6 the development wells shut-in wellhead pressures have been plotted against the well depth.

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Development wellsShut-in pressure v.s. well depth, sorted

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

22000

24000

0 10 20 30 40 50 60 70 80 90Cumulative percent

Wel

ldep

th(fe

et)/S

hut-i

npr

essu

re(p

si)

Shut-in test pressure (psi) True vertical depth (ft) Expon. (True vertical depth (ft))

Figure 6.6 Development wells shut-in wellhead pressures plotted against well-depth Exploration drilling There were in total 508 exploration wells listed with a shut-in wellhead pressure on the first well test after completion. In Figure 6.7 the exploration wells shut-in wellhead pressures have been plotted against the well depth.

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Exploration wellsShut-in pressure v.s. well depth, sorted

0

20004000

60008000

1000012000

14000

1600018000

2000022000

24000

0 20 40 60 80 100

Cumulative percent

Wel

ldep

th(fe

et)/S

hut-i

npr

essu

re(p

si)

Shut-in test pressure (psi) True vertical depth (ft) Expon. (True vertical depth (ft))

Figure 6.7 Exploration wells shut-in wellhead pressures plotted against well depth When looking at Figure 6.7 it is important to note that the number of wells drilled is based on only the exploration wells that have been completed as producers and listed with a well test with a positive pressure. If looking at the Mobile area, 33 exploration wells have been drilled to more than 20000 feet (6100 meters) in the period 1980 - 1996. These wells are likely all HPHT (more than 10000 psi) wells. In the Destin Dome Blocks six wells have been drilled in the same formation as the Mobile wells. In the Pensacola one well has been drilled. In addition 401 exploratory wells have a well depth between 16000 – 20000 feet. By reviewing the test pressures for development wells drilled in the same block and evaluating shut-in test pressure and the well spud dates, at least 57 of these were likely to be HPHT wells (close to 10000 psi or above). Further, some of the wells drilled to less than 16000 feet have been HPHT wells. It is then likely that it has been drilled in the range of 100 to 200 exploration HPHT wells in the US GoM OCS in the period 1980 - 1998.

6.3.2 Norwegian Drilling Wells The number of HPHT wells drilled in Norway is shown in Table 6.7. The data from before 1996 stems from the NPD daily drilling report system (DDRS). The data from 1996 and later stem from the report ”Utvikling i risikonivå norsk sokkel”, hovedrapport, Fase 6 – 2005, www.ptil.no .

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Table 6.7 Number of HP/HT wells drilled in the Norwegian waters sorted on years No. of HPHT wells (>690 bar and/or > 150oC) Year

Exploration Production 1984 3 1985 2 1986 2 1987 0 1988 3 1989 3 1990 8 1991 7 1992 9 1993 5 1994 3 1995 2 1996 3 4 1997 5 1 1998 2 1 1999 4 2 2000 2 2001 3 2002 3 2 2003 2 1 2004 2 10 2005 3 20 Total 76 41

6.3.3 US GoM OCS Wells in Production The pressure exposure data for production wells are based on all the well tests with a listed shut-in wellhead pressure in the period 1980 – 1996 (/1/). Totally 48264 tests were listed with a positive wellhead shut-in pressure. Many well tests were not listed with well test pressures. The distribution of well tests in four different pressure ranges is presented in Table 6.8. Table 6.8 Pressure ranges in production wells in US GoM OCS wells Pressure range No. of

well tests Relative

distribution below 6000 psi (414 bar) 46928 97,23 % 6000 – 8000 psi pressure 926 1,92 % 8000 – 10000 psi 336 0,70 % more than 10000 psi (690 bar) 74 0,15 %

Total 48264 100,00 %

In Figure 6.8 the development wells shut-in wellhead pressures have been plotted against the well depth.

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Figure 6.8 All well tests performed 1980-1996 and listed with a shut-in wellhead pressure

6.4 Production Rates and Gas Oil Ratio Data, US GoM OCS

This section is based on MMS Ogor A files from 1980 – 1999 (/1/). These files list the well individual production amount (gas, oil and water) for each month. Only the December data each year has been used to reduce the amount of information to handle

6.4.1 Production Rates Figure 6.9 and Figure 6.10 show the production rate for the US GoM OCS oil and gas wells respectively. The production rate data has been grouped in two different groups, the 80-ties and the 90-ties.

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0

20

40

60

80

100

120

140

160

180

200

0% 10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Perecentage of oil wells

Oil

prod

uctio

n(m

3/da

y)

Daily Oil Volume in the 80's Average 80'sDaily Oil Volume in the 90's Average 90's

Figure 6.9 Oil well production rates, US GoM OCS wells, 1980 - 1999 The number of wells in production in the December month was slightly higher in the 90's than in the 80's. The average produced amount of oil was 41 m3/day in the 90's and 36 m3/day in the 80's per oil well that produced in the December month. In the end of the 90's some wells have experienced flow-rates of more than 3000 m3/day. The highest flow-rate seen was 5600 m3/day (or approximately 35 000 bbls). The wells are only those wells categorized as oil wells in the MMS files (some of them were only producing gas, and no oil). Nearly 99% of these wells have also produced gas, in average 13013 Sm3/day. Water production was also listed for 88% of these wells. On average for all wells the water production was 49.5 m3/day, i.e. more water was produced than oil.

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0

50000

100000

150000

200000

250000

300000

350000

400000

450000

500000

0% 10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Perecentage of gas wells

Gas

prod

uctio

n(S

m3/

day)

Daily Gas Volume 80'sDaily Gas Volume 90'sAverage 80'sAverage 90's

Figure 6.10 Gas well production rates, US GoM OCS wells, 1980 - 1999 The number of wells in production in the December month was slightly higher in the 90's than in the 80's. The average produced amount of gas was 108 000 Sm3/day in the 90's and 124 000 Sm3/day in the 80's per gas well that produced in the December month. The best producers produced nearly one million Sm3/day. The wells are only those wells categorized as gas wells in the MMS files (some few of them were only producing oil, and no gas). Approximately 66% of these gas wells also produced oil, in average 7.3 m3/day for all the wells. Water production was also listed for 67% of these wells. In average for all wells the water production was 18.2 m3/day.

6.4.2 Gas Oil Ratio The gas oil ratio data has been grouped in two different groups, the 80-ties and the 90-ties.

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0

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Perecentage of oil wells

Sm

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GOR 80's (Sm3/Sm3)GOR 90's (Sm3/Sm3)

Figure 6.11 Well test GOR data sorted on period

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(Sm

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Figure 6.12 Well test GOR data sorted on period

6.5 Workover Frequency Exposure Data

Very little statistical material related to number of workovers carried out exists. From the SINTEF study "Reliability of Surface Controlled Subsurface Safety Valves, Phase III", SINTEF report STF 75 F89030, it was observed 498 workovers on a total of 7790 well years. The data was mainly collected in the period 1985 - 1989 for North Sea wells. This gives in average:

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15.6 well years per workover The NPD Annual reports from 1980 to 83 lists the number of workovers carried out the actual year alongside the number of production wells. A total of 88 workovers were listed and a total of 731 production well years. This gives in average:

8.3 well years per workovers In the autumn 2001 a search in the NPD Daily Drilling Report System (DDRS) was carried out. The search criteria specified: • Traditional type of equipment was used (i.e. the permanently installed drilling rig and not a

coiled tubing or snubbing unit). • The main operation was Workover • Sub operation was completion string (i.e. involved pulling of the completion string). Each well that had at least on occurrence with the above combinations within one year was counted as a workover. This means that if two workovers were carried out the same year it will be counted as one workover only. On the other hand if the workover starts in December one year and is completed in January the next year it will be counted as two workovers. This count of workovers has been possible for the period after 1995 when NPD introduced some new codes in the DDRS. Seventy-six workovers were carried out in the year 2000. The result from this count for the years 1996 to 1999 is shown in Table 6.9. Table 6.9 Workover frequencies in Norwegian waters

Year No. of workovers

No. of prod-uction wells

No. of inject-ion wells

Sum no. of wells

No of well years per workover

1996 56 580 189 769 13.7 1997 72 612 194 806 11.2 1998 86 624 211 835 9.7 1999 59 854 259 1113 18.9

Total 273 2670 853 3523 12.9

It seems that the workover frequencies related to conventional workovers has decreased since the beginning of the 1980-ties when comparing with the above results. It is recommended that 10.6 well years per workover is used for the estimates related to blowout/well release frequencies per workover operation. This value will represent the average for the period 1980 - 2000.

6.6 Wireline Frequency Exposure Data

Very little statistical material related to number of wireline runs exists. To establish an estimate for wireline exposure data, experience from the Ekofisk field in 1992 has been used. In 1992, 135 wells were in service (production and injection). A total of 220 wireline jobs were carried out. If in average each wireline job includes 2.5 wireline runs a total of 550 wireline runs were carried out for the 135 wells. This gives in average:

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4.2 wireline runs per well year or 1.7 wireline jobs per well year

It is important to note that the Ekofisk field mainly has wireline retrievable SCSSVs, and not tubing retrievable SCSSVs that most operators prefer when completing new wells today. It should further, be noted that most likely several minor incidents (small gas releases) during wireline jobs have never been recorded as blowouts.

6.7 Coiled Tubing and Snubbing Exposure Data

Table 6.10 lists the number of coiled tubing and snubbing workovers that have been carried out in the Norwegian waters in the period 1984 - 1995. The NPD Daily Drilling Report System (DDRS) was used to extract the data. The data may not be exact because the DDRS did not include a specific code for these operations before 1995. The results are based on a search in the activity description for all production wells stored in the database. Coiled tubing and snubbing activities during regular drilling and completion are not included in Table 6.10. Coiled tubing and snubbing operations carried out, as a part of a conventional workover, is included. These operations should not have been included because they were only a sub-operation during a conventional workover. Therefore the activity level as listed in Table 6.10 probably is 10 – 20% higher than the real figures. Table 6.10 Coiled tubing and snubbing workover exposure data for the Norwegian sector of the

North Sea, 1984 - 1995 Year Snubbing workovers Coiled tubing workovers 1984 1 0 1985 5 1 1986 5 3 1987 7 5 1988 8 3 1989 12 13 1990 4 16 1991 15 13 1992 28 19 1993 21 32 1994 33 38 1995 49 48 Total 188 191

In the autumn 2001 a search in the NPD Daily Drilling Report System (DDRS) was carried out. The search criteria specified that either a snubbing or a coiled tubing unit was used. The main operation was Workover and the sub operation was not specified. Each well that had at least on occurrence with the above combinations within one year was counted as a snubbing workover or a coiled tubing workover. This means that if two operations were carried out the same year it will be counted as one operation only. On the other hand if the operation starts in December one year and is completed in January the next year it will be counted as two operations. If dedicated snubbing or coiled tubing units are used in association with a conventional workover they will be regarded as separate operations, i.e. the total number of operations indicated in Table 6.11 may be

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some higher than the real figures. The result from this count for the years 1996 to 2000 is shown in Table 6.11. Table 6.11 Coiled tubing and snubbing workover exposure data for the Norwegian sector of the

North Sea, 1996 - 2000 Year Snubbing workovers Coiled tubing workovers 1996 42 83 1997 39 81 1998 32 83 1999 30 49 2000 24 50 Total 167 346

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7. Overall Blowout/Well Release Frequencies

Only overall blowout/well release frequencies for the different operational phases have been calculated. If required, analyses that are more detailed can be carried out by using the information presented in the various tables in the previous sections and/or the SINTEF Offshore Blowout Database. The listed frequencies in this section are based on the experience from US GoM OCS, UK and Norway in the period 1980-01-01 - 2005-01-01 only. The blowout frequencies during the different operational phases are presented in Table 7.1 to Table 7.6. The four blowouts listed with the phases “Unknown” and Unknown drilling” are not included. Please also note that blowouts caused by external loads are disregarded when calculating the blowout/well release frequencies. Table 7.1 Blowout/well release frequencies during completion (based on Table 4.4, Table 5.1,

Table 5.2, and Table 5.4)

Category No. of completions* No. of incidents No. of completions per incident

No. of incidents per completion

Blowout (surface flow) 20 328 9 2171 0.00046 Blowout (underground flow) 20 328 0 - 0Well release 20 328 6 3256 0.00031 Diverted well release 20 328 0 - 0Total 20 328 15 1302 0.00077 * Based on total number of wells completed in Table 5.1, number of developments wells drilled in Table 5.2, and

Table 5.4.

Table 7.2 Blowout/well release frequencies during development drilling (based on Table 4.4 and Table 5.11)

Category Type of incident

No. of dev. wells drilled

No. of incidents

No. of drilled wells per incident

No. of incidents per drilled well

Deep 22 833 8 2854 0.00035 Blowout (surface flow) Shallow 22 833 22 1038 0.00096

Deep 22 833 3 7611 0.00013 Blowout (underground flow) Shallow 22 833 1 22833 0.00004

Deep 22 833 0 - 0 Diverted well release Shallow 22 833 16 1427 0.00070

Deep 22 833 5 4567 0.00022 Well release Shallow 22 833 2 11417 0.00009 Total 22 833 57 401 0.00250

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Table 7.3 Blowout/well release frequencies during exploration drilling (based on Table 4.17,Table 5.1, Table 5.2, and Table 5.4)

Category Type of incident

Exploration well type

No. of. wells drilled

No. of incidents

No. of drilled wells per incident

No. of incidents per drilled well

Appraisal 6257 9 695 0.00144 Deep Wildcat 7505 13 577 0.00173 Appraisal 6257 8 782 0.00128 Wildcat 7505 14 536 0.00187 Shallow Unknown - 1 - -

Blowout (surface flow)

Total 13762 45 306 0.00327 Appraisal 6257 0 - 0 Deep Wildcat 7505 7 1072 0.00093 Appraisal 6257 0 - 0 Shallow Wildcat 7505 0 - 0

Blowout (underground flow)

Total 13762 7 1966 0.00051 Appraisal 6257 2 3129 0.00032 Shallow Wildcat 7505 7 1072 0.00093 Diverted well

release Total 13762 9 1529 0.00065

Appraisal 6257 3 - 0 Wildcat 7505 3 - 0 Deep Unknown - 2 - - Appraisal 6257 2 3129 0.00032 Shallow Wildcat 7505 2 3753 0.00027

Well release

Total 13762 9 1529 0.00065 Appraisal 6257 1 6257 0.00016 Deep Wildcat 7505 0 - 0 Unknown

Total 13762 1 13762 0.00007 Appraisal 6257 13 481 0.00208 Wildcat 7505 23 326 0.00306 Deep Unknown - 1 - - Appraisal 6257 11 569 0.00176 Wildcat 7505 22 341 0.00293

All

Shallow Unknown - 1 - -

Total exploration drilling 13762 71 194 0.00516

Table 7.4 Blowout/well release frequencies during production (based on Table 4.4 and Table 5.17). Blowouts caused by external loads (storm, fire etc.) are disregarded

Category No. of well years in service

No. of incidents

No. of well years per incident

No. of incidents per well year

Blowout (surface flow) 211 142 7 30163 0.000033 Blowout (underground flow) 211 142 1 211142 0.000005 Diverted well release 211 142 0 - 0 Well release 211 142 2 105571 0.000009 Total 211 142 10 21114 0.000047

Table 7.5 Blowout/well release frequencies during well workover (based on Table 4.4, Table 5.17 and Section 6.5)

Category No. of workovers* No. of incidents

No. of workover per incident

No. of incidents per workover

Blowout (surface flow) 19 920 20 996 0.00100 Blowout (underground flow) 19 920 0 - 0 Diverted well release 19 920 0 - 0 Well release 19 920 17 1172 0.00085 Total 19 920 37 538 0.00186 * Based on in average one workover per 10.6 production well years (Section 6.5)

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Table 7.6 Blowout/well release frequencies during wireline (based on Table 4.4, Table 5.17 and Section 6.6)

Category No. of wireline jobs*

No. of incidents

No. of wireline jobs per incident

No. of incidents per wireline job

Blowout (surface flow) 358 941 4 89735 0.000011 Blowout (underground flow) 358 941 0 - 0 Diverted well release 358 941 0 - 0 Well release 358 941 4 89735 0.000011 Total 358 941 8 44868 0.000022 * Based on in average 1.7 wireline jobs per production well years (Section 6.6)

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REFERENCES

1 Files retrieved from/bought from Mineral Management Service in the US: • http://www.gomr.mms.gov/homepg/pubinfo/freeasci/freedesc.html (used for

downloading files related to well drilling and well production data) • File: 5137 Historical Well Test by Area and Block ASCII (bought from MMS) • Ogor A, Well production files bought from MMS (1980 –1996) • Ogor A, Well production files downloaded from MMS (1996 –2005) US GoM region • Ogor A, Well production files downloaded from MMS (1986 –2005) US Pacific

region