Basic Wellbore Validation

Nov 2016

Document History & Control

Version Date Author

0.1 18 Oct 2016 Steve Hawtin

0.2 21 Nov 2016 Steve Hawtin

© Crown copyright 2016

You may re-use this information (not including logos) free of charge in any format or medium, under the terms of the Open Government Licence.

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Any enquiries regarding this publication should be sent to us at Oil & Gas Authority Limited.

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1 Introduction

One of the responsibilities of the Oil and Gas Authority (OGA) is to provide accurate and trusted data

about the UK’s oil industry related activities. A key element of that commitment is to ensure that a

reliable list of wells and their characteristics is available. For a variety of historical reasons the data

that the OGA currently holds about wellbores is inadequate. There are missing values and

inconsistent attributes that mean the data fails to achieve the minimal standards required to be of value

to the OGA and its customers. In order to address this issue the OGA has undertaken a project to

drive immediate improvement in the quality of its wellbore data collection.

This document is in three parts: first there is an outline of the minimal data standards; next it lists the

quality checks that the OGA will carry out; and finally it describes a tool to identify quality issues and

make it easier for companies to submit corrected values.

Figure 1: Wellbore attribute quality issues (for all offshore wells)

The responsibility for maintaining and reporting data about wellbores rests with the original licensees

and their successors. So where there are data quality issues the corrected values must be supplied by

these companies. In order to smooth this process the OGA has constructed a spreadsheet based tool

that shows the data the OGA holds and where it fails to achieve the listed minimal quality standards.

The tool will be supplied to each responsible company pre-populated with the wellbores that the OGA

has assigned to them. Chapter 4 in this document (page 24) gives an introduction to the tool and

explains how it can be used. By manipulating values in this tool the licensee is able to address

identified data issues. When this review and correction work is completed the results can be

dispatched back to the OGA who will apply the proposed corrections.

It is the OGA’s intention to create a comprehensive data standard for wellbore data at some future

time. It is expected that this will require input from industry and will result in a detailed wellbore data

standard. However, since the task of creating a complete standard will take some time it was felt that

a focused project to bring the existing data to a bare minimal standard was the most immediate

priority. When the full standard is published it is expected that the OGA will approach the

responsible companies to obtain the values of additional wellbore attributes.

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1.1 Contents

1 Introduction ..................................................................................................................................... 1

1.1 Contents .................................................................................................................................. 2

1.2 Assistance, advice, queries or suggestions .............................................................................. 2

2 Minimal Wellbore Data .................................................................................................................. 3

2.1 Intrinsic Attributes .................................................................................................................. 4

2.2 Mandatory Attributes .............................................................................................................. 9

2.3 Optional Attributes ................................................................................................................ 19

3 Quality Tests ................................................................................................................................. 21

4 Wellbore Validation Tool ............................................................................................................. 24

4.1 The Overall Process .............................................................................................................. 27

4.2 Control Tab ........................................................................................................................... 28

4.3 Wellbores Tab ....................................................................................................................... 29

4.4 Original Data Tab ................................................................................................................. 30

4.5 Rules Tab .............................................................................................................................. 30

4.6 Expect Attributes Tab ........................................................................................................... 31

4.7 Constants Tab ........................................................................................................................ 31

4.8 Tests and Summary Tabs ...................................................................................................... 31

4.9 Reference List Tabs .............................................................................................................. 31

1.2 Assistance, advice, queries or suggestions

The OGA has invested effort to make it as easy as possible for companies to participate in this data

quality initiative. There are, however, still liable to be issues that are not adequately addressed in this

short document. If you have any questions, suggestions or comments about this document, the data

fixing tool or any other aspect of this project please send them to:

Steve Hawtin steve.hawtin@ogauthority.co.uk +44 (0)300 0201689 Sharon Matthew sharon.matthew@ogauthority.co.uk +44 (0)300 0201077 Andy Thompson andrew.thompson@ogauthority.co.uk +44 (0)300 0201667

Phil Harrison phil.harrison@ogauthority.co.uk +44 (0)300 0671615

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2 Minimal Wellbore Data

In order for any set of data to be worth employing it must achieve a certain minimal level of quality.

If it fails to do so then the lack of trust placed in the data dramatically reduces the impact it can have.

The list of wellbores held by the OGA is an important component in decisions taken both within The

Authority and externally.

It is not uncommon for those that utilise the OGA data to raise concerns about its quality. These

comments are often rooted in particular anecdotes, where an attempt to draw conclusions has been

frustrated by missing values or apparent inconsistencies. Individual instances are important, but to

sustain improvement in data quality a more systematic approach has to be applied. In other words it is

hard to measure data quality unless you first define and document at least some kind of “minimal

standard” that data can be diagnostically compared against.

A comprehensive data standard would document a number of aspects:

The business justification for gathering and sustaining the data

The key activities that employ the data, exploring which components have most impact

The people and roles that create, manipulate or consume the data

A description of the systems of record that hold the definitive versions of data, as well as an

indication of the key systems that consume it or contribute to it

The data structure, including reference values and conventions

A systematic list of mandatory and indicative quality rules to be applied (preferably in both

a widely understood form and in one or more formally implementable constructs)

A register of the key related categories of data that have dependencies, or that deliver

dependencies

A list of those involved with defining, approving and updating the data standard

An outline of the way standards for the data are to be updated as business needs evolve

At some future date the OGA will, in consultation with industry, create this type of more

comprehensive data standard for wellbores. However, in the meantime, the wellbore data held by

OGA needs immediate improvement.

This document is an intermediate definition that contains some of these components and explains the

“minimal standard” that wellbore data should achieve in the short term. This chapter focuses on the

structure of wellbore data; that is the attributes and reference values.

The attributes of a wellbore have been divided into three groups:

Intrinsic: the attributes that identify a particular wellbore such as the well number

Mandatory: attributes that are required and must adhere to certain conventions

Optional: additional attributes that may be supplied at the discretion of those responsible

This chapter mirrors those three topics, each of which has its own section.

There are some general points that are worth making about the attributes. Where there are distances

specified it is to be assumed that the units of measure are metres. This simplifies the definition of the

wellbore structure since it removes the requirement to define specific units of measurement for every

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length based attribute. If values need to be converted from “feet” (where no specific type of foot is

indicated) it should be assumed that “International Feet” are intended, that is that one foot is exactly

0.3048m.

In the UK sector there are few occasions when text values require accented characters or unusual

symbols. Therefore, unless explicitly allowed, most text values should be confined to the 7bit ASCII

character set unless specific steps are taken to explain why this is inadequate.

2.1 Intrinsic Attributes

These attributes are those employed in order to ensure that the wellbore is unambiguously defined.

The value of these attributes has been supplied by OGA and, in most cases, it is expected that any

issues with them will be addressed by OGA. The one obvious exception is the

“RESPONSIBLE_COMPANY” field; in this case there may be a dispute about which company

should supply the information. This can be indicated by modifying this attribute in the relevant

wellbores (in column ‘B’). Of course if the company feels that any of these intrinsic values should be

corrected they can signify this by editing it.

The intrinsic attributes applied here are:

WELLREGNO Wellbore Registration Number

RESPONSIBLE_COMPANY Responsible Company Group

COUNTRYCOD Legislative Area

QUADRANTNO Quadrant

BLOCKNO Block Number

BLOCKSUFFI Block Suffix

PLATFORM Platform Letter

DRILLSEQNO Drilling Sequence Number

WELLSUFFIX Well Suffix

DENNO DEN Number (internal OGA use)

2.1.1 Wellbore Registration Number – The Identifier

The OGA well Registration number must be quoted in full on all returns well logs, reports and

correspondence. PON1 12 defines the registration number as consisting of:

Country: one character code to define the regulatory authority covering the well

Quadrant: the number, or letter, of the quadrant in which the well is drilled. UK quadrants

are areas enclosed by one degree of latitude and longitude

Block: the number of the block within the quadrant in which the well is drilled

Block Suffix: a single lower case letter indicating which licence block the well was within

Platform: offshore platform, subsea cluster designation or land site2

Drilling Sequence: the well’s drilling sequence number as assigned by the OGA

Well Suffix: a single capital letter that indicates when the wellbore is a respud or sidetrack

1 Petroleum Operating Notices define specific requirements and reporting obligations for UK Exploration and

Production activities https://www.ogauthority.co.uk/exploration-production/petroleum-operations-notices/ 2 PON 12 states that the “platform” component of the OGA registration number either contains a single upper

case alphabetic character or a blank. The naming convention actually employed by OGA uses a space when

there is no platform letter present.

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These components of the name also appear as independent attributes within the wellbore, this use will

be outlined in more detail below. One might assume that combining the current values of these

attributes of a wellbore would deliver the identifier; unfortunately this is not quite correct. For a

number of historical reasons these “intrinsic” attributes have been modified (to reflect changes or to

correct anomalies) after the well name was selected.

Here are some examples of valid well names:

97/12- 1: The first well drilled in the 97/12 block

15/27- 5: The fifth well drilled in the 15/27 block

15/27- 5Z: The first side-track on the 15/27-5 well

15/26a- 6: The sixth well drilled in the 15/26 block, which happens to have been drilled

within the “a” licence sub-block

15/26a- 6A: The first respud of the 15/26a-6 well

15/26b-W1: The first well drilled from the W platform, which happens to be in the 15/26b

licence sub-block

L97/10- 10: The tenth well in the 97/10 block (an on-shore well)

L97/10-A1: The first well drilled from the land based A ‘platform’ in block 97/10

LO/06- 6: An onshore well drilled in the “O” quadrant (which happens to be in the onshore

licence block “SK62a”)

LO/06- 5: An onshore well drilled in the same “O/06” block but in a completely different

onshore licence block (in this case the onshore licence block “SK52a”)

M112/19- 1: An offshore well drilled in the 112 quadrant but within the Isle of Man’s

territorial waters

2.1.1.1 Well Aliases

There are a few occasions where a well has been “aliased”. For example if an exploration well is

subsequently hooked up to a platform it can end up with two distinct well registration numbers.

Figure 2: Three stages in the development of the Saxon field

An example of this occurs in one of the wells in the “Saxon” field. It was originally drilled as a

sidetrack of the 21/23b-7 well. The ‘S’ platform was placed on top of this well and the 21/23b-S1

well was drilled. When the 21/23b-7 sidetrack was attached to the platform it was given the alias of

21/23b-S2. Subsequently two further sidetracks were drilled and assigned the names 21/23b-S2Z and

21/23b-S2Y. If aliases are ignored one might expect the wellbore 21/23b-S2 to exist (given that the

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S2Z well is a sidetrack of it), however all its well data is maintained under the 21/23b-7Z wellbore.

This single well origin has some wellbores numbered in sequence by the block and some by the

platform so it has the potential to deliver false positives on Rule 66.

2.1.2 Responsible Company

This attribute defined the company group that are responsible for the well. PON9 states that

“Obligations towards the OGA for Licence Data are borne jointly and severally by all companies who

are party to a licence and not by the Operator of that licence alone” therefore responsibility for the

well rests with the company that originally drilled the well, its partners and successors.

The obligation to maintain the wellbore data is imposed “in perpetuity” (in practice it remains until

the OGA acknowledges in writing that all the necessary data has been delivered to a suitable

repository, for example to the NHDA). Given this wide ranging responsibility it may seem

counterintuitive to assign responsibility to a single company group. In practice however it is usually

obvious who the “lead partner” has been for a particular well over the course of its lifecycle and that

single organisation will usually hold the most trustworthy records. In cases where the “lead partner”

is no longer able to deliver the data (for example the company has ceased trading) then the OGA will

pursue the other partners to fulfil these obligations.

2.1.3 Country

This wellbore attribute is a single character code used to define the regulatory regime under which the

well was drilled. It can take on the following values:

<Blank>: An empty value indicates that this is an offshore well

‘L’: This indicates that the well was drilled onshore

‘M’: Indicates wells drilled under the jurisdiction of the Isle of Man

This could easily be confused with the more common definition of the word, which would be a nation

recognised by the United Nations. All the wells listed belong to the United Kingdom, but this is not

what this attribute indicates.

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2.1.4 Quadrant

Figure 3: UK Quadrants are employed for naming wells

The quadrant containing the well, this has either a quadrant number (from 1 to 449) or a single upper

case letter (from ‘A’ to ‘Y’). The way quadrants have been assigned means that there is a complex

relationship between the quadrant’s identifier and the area it indicates. In addition (as section 2.2.6

discusses) the exact definition of the quadrant’s corner locations depends on the relevant geodesy.

2.1.5 Block

Figure 4: Each quadrant is divided into 30 blocks

This attribute holds the number of the block containing the well. The block number is a two digit

number from 01 to 30. This subdivision of the quadrant is employed to name wells that are both

onshore and offshore.

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There are two other distinct elements that are also commonly referred to as “blocks”. When dealing

with onshore locations the Ordnance Survey grid is divided into 10km squares that are often referred

to as blocks, in this context these are called “OS Blocks”. The other place where the word is used is

to refer to licenced blocks (which are often subdivisions of blocks or OS blocks). Where these

variants are used they have been tagged

2.1.6 Block Suffix

A block suffix is a single lower case letter used to indicate that the block has been subdivided. When

part of a licence is initially relinquished the retained part is assigned the suffix ‘a’, subsequent re-

licencing may create licenced sub-blocks indicated by the letters ‘b’, ‘c’ and so on.

The licence block suffix may, or may not, form part of the OGA well number. If, for example, a well

was drilled before the block was sub-divided then its name may omit the block suffix (even if the

wellbore has the “Block Suffix” attribute set).

2.1.7 Platform

If the well was drilled from a platform then this is indicated with a single upper case letter.

2.1.8 Drilling Sequence Number

The Drilling Sequence Number (DSN) is the consecutive chronological number of the well within the

block or from the ‘platform’, consisting of digits with no leading zero. When this document was

written no drilling sequence number required more than two digits. The chronological sequence

number is allocated to the well only after it has commenced drilling to a specific bottom-hole target

location, as follows:

exploration, appraisal or single satellite subsea development wells will normally be

numbered at the time a well is spudded i.e. when drilling commences from surface

wells forming part of a multi-well development, in which casings are batch set prior to

finalising the slot/target allocation, will be numbered only after drilling has commenced to a

specific target location, normally at the time of drilling out of the 20”, or equivalent, surface

casing shoe

Any proposed well that has not yet started drilling should have a blank sequence number. This

presents a potential problem when identifying the well since its name will appear to be invalid.

It should be noted that the “Drilling Sequence Number” is quite distinct from the “Wellbore Sequence

Number” and the two should not be confused. The drilling sequence number is an integer; the

wellbore sequence number should be in the form of “WB1”, “WB2” and so on.

2.1.9 Well Suffix

The well suffix is a single capital letter that distinguishes different related wellbores. There are three

reasons for adding a well suffix letter:

Re-spud: If a well is re-spudded for any reason, it is distinguished by an upper case

character ‘A’, ‘B’, ‘C’, etc.

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Sidetrack: If a well is sidetracked and the abandoned part of the hole has significant data

(i.e. logs, MWD and/or core), the sidetrack is distinguished by ‘Z’, ‘Y’, ‘X’, etc.

Redrill: the letter ‘R’ is employed to indicate that a well has been redrilled, this should

therefore never appear as a suffix on the well number

In PON 12 it is suggested that ‘platform’ wells cannot have respuds, however this seems to contradict

the data.

When a sidetrack is for strictly mechanical reasons and the abandoned part of the hole does not have

significant data (i.e. logs, MWD and/or core) and is not through any known hydrocarbon bearing

interval the suffix is supposed to be not required. However, again the existing data values seem to

contradict this.

2.1.10 DEN Number

This is an internal code employed by the OGA to manage hardcopy data about off-shore wells and

should not require any input from the company.

2.2 Mandatory Attributes

Having employed the intrinsic attributes to identify the wellbore the following attributes provide a

minimal set:

WELL_ORIGIN Well Origin

WELLBORE_SEQUENCE Wellbore Sequence Number

FIELD Field Name

TOPHOLEDTM Top Hole Coordinate Reference System

TOPHOLEYDD Top Hole Latitude

TOPHOLEXDD Top Hole Longitude

BOTHOLEDTM Bottom Hole Coordinate Reference System

BOTHOLEYDD Bottom Hole Latitude

BOTHOLEXDD Bottom Hole Longitude

DATUMELEV Elevation of the well datum (in m)

DATUMTYPE Well datum type

GROUNDELEV Ground height above sea level (for on-shore wells)

WATERDEPTH Depth of water (for offshore wells)

TOTALMDDRI Total measured depth (from well datum)

TVDSSDRILL Total vertical depth (from sea level)

ORIGINAL_LICENCE The full original licence designation

LICENCE_TYPE The type of the original licence

OPERATOR The name of the current operating company (for active

wells)

ORIGINTENT The original purpose of the well

SPUDDATE The date the wellbore was started

DATETDREAC The date the deepest extent was reached

COMPLEDATE The date the wellbore was completed

COMPLESTAT The current status of the wellbore

FLOWCLASS The types of liquid present

VERIFICATION_COMPANY The name of the company that last validated the data

VERIFICATION_DATE The date when the data was validated

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2.2.1 Well Origin

Figure 5: A single well can combine multiple wellbores3

The entities being discussed here are actually wellbores, some of which are related to each other

through sharing a common origin at the surface. This attribute defines the name of the wellbore that

provides the surface location of this one. For wells with no respuds or sidetracks the well origin name

and the well registration number will be the same. If the wellbore is a sidetrack the well origin should

be the name of the initial wellbore that shares a surface location, for example the well called

“110/02b-R3” has a well origin of “110/02b-R3” while “110/02b-R3Z” shares an origin and hence

also has a well origin value of “110/02b-R3”. When a further sidetrack to “110/02b-R3Z” was drilled

(called “110/02b-R3Y”) its well origin was also “110/02b-R3”.

In the UK this is made harder to track because the wellbore name may be changed for certain

sidetracks. One example of this is the well 9/13-A7; this well was completed in 1977 and was a

producer. In 1993 the well 9/13-A54 was drilled as a sidetrack of the 9/13-A7 well. Because 9/13-A7

had a production history and yet had ceased production this new wellbore was assigned a new drilling

sequence number. Again in 2013 another sidetrack was drilled, this time it was assigned the number

9/13a-A85. The insertion of the additional “a” indicates that by this time the original licence had been

subdivided.

This type of process (where a sidetrack is drilled to regain production from a previously producing

well) is called “slot recovery”. Generally the operation will involve abandonment (to AB1, see page

17) of the donor wellbore at some point above the reservoir, as deep as possible to avoid redrilling the

overburden, but providing a sufficient angle to reach the new target. In the case of A54, the kick off

point was at 3346 feet (1019.8608m) so there is a lot of the original A7 wellbore still in use by A54

and A85.

3 This diagram is from the PPDM “What is a Well” document available from https://whatisawell.ppdm.org/

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The well origin is not accessible using the current set of OGA data, so this has been deduced from the

CDA data. There are three types of cases:

Any OGA wellbore that is apparently absent from the CDA data has been assigned its own

name as the well origin

Where the well origin noted in CDA appears absent from the OGA wellbores a “reasonable

wellbore” has been assigned. This occurs in six cases 110/13a-E1, 206/08- 3, 211/26- 10Z,

22/11- 5R01, 48/17a- 11 (which seems to be a misspelling for 48/17a-E1) and 9/13b- 25

Where the well origin in CDA matches a well in OGA that has been used

Figure 6: Wellbores cannot have well origins that are not the primary wellbore

The intention is that the well origin is the initial well at the given surface location, in other words only

wellbores with wellbore sequence numbers of “WB1” can act as well origins. To reiterate the target

wellbore for the well origin property must always have itself as its own well origin.

2.2.2 Wellbore Sequence Number

The wellbore sequence is another element from the PPDM system. This provides a numeric indicator

of which wellbore this is within a single well origin. The wellbore sequence numbers are of the form

“WB1”, “WB2” and so on.

Figure 7: Multiple wellbores sharing the same origin

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The example shown schematically in Figure 7 above, shows the ten wellbores that all originated in the

11B slot of the A platform in block 16/26. In this case there were four different phases of production:

16/26-A17 staring in 1996; 16/26-A35 starting in 2000; 16/26-A57 starting in 2006; and finally

16/26-A59 starting in 2009.

2.2.3 Field

This attribute defines the name of the field primarily associated with a particular well. If there is no

recognised field then this may be the special string “NOT IN FIELD”. The spreadsheet provides a list

of the OGA recognised field names in the “_FIELDS” tab. This attribute should be selected from that

list. If this constraint is too restrictive then the list may be extended through discussion with OGA.

There is an active project to define a system of records for OGA fields. This may impact the field

attribute of wellbores.

2.2.4 Licence Type

This indicates the licence type under which the well was drilled. For offshore wells there is just one

type of licence:

‘P’: A production licence

For land wells there is a longer list of licence types:

‘AL’: Appraisal Licence

‘CE’:

‘DL’: Development Licence

‘EXL’: Originally a new type of Exploration Licence (from the 1984 act) these have now all

been converted to apply the same terms as ‘PEDL’

‘ML’: Mining Licence old style licence from the 1950s

‘PEDL’: Petroleum Exploration and Production Licence

2.2.5 Original Licence

This attribute provides the licence number under which the well was drilled. For offshore wells the

licence number will always be “P” followed by an integer, the integer value will be at least 3 digits

long, padded with leading zeros if necessary.

In the CDA data this attribute is called the “Licence Number”; this should not be confused with the

numeric part of the licence number, so a valid value for this attribute would be something like “P456”

rather than the bare number “456”.

2.2.6 Coordinate Reference Systems (Geodetic Datum)

TOPHOLEDTM Top Hole Coordinate Reference System

BOTHOLEDTM Bottom Hole Coordinate Reference System

The surface hole and bottom hole positions each have a “geodetic datum” attribute that specifies how

to interpret the location. It is important that one of the permitted reference datums is specified and

that all calculations employ the appropriate operations.

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Figure 8: Selecting which geodetic datum to use

There are three Coordinate Reference Systems employed in the UK oil industry:

ED 50: for offshore positions East of the “Thunderer Line”

ETRS89: for offshore positions West of the “Thunderer Line”

OSGB 1936: for positions that are onshore

The “Thunderer Line” is a dividing line running North/ South at 6°W (in ED 50). The European

Survey Petroleum Group (EPSG) defines the following codes for these three CRS’s:

4230: geographic 2D – ED 50

4258: geographic 2D - ETRS89

4277: geographic 2D - OSGB 1936

Most GPS systems report their position in the WGS84 datum. For practical purposes this is identical

to the ETRS89 datum that is used west of the Thunderer line. Any datum shift that has to be applied

should employ the “Common Offshore” transformation, that is the full 7 parameter shift defined in

EPSG (with the Coordinate Transformation codes 1311, 1314 and 1315) rather than one of the

simpler 3 or 4 parameter shifts.

2.2.7 Original surface position

TOPHOLEYDD Top Hole Latitude

TOPHOLEXDD Top Hole Longitude

The position at the surface is defined in terms of the longitude and latitude (in the selected Geodetic

Datum). This is expressed as a pair of real numbers (that is not using degrees minutes and seconds).

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It is common practice (although not strictly correct) to enter a single “platform location” as the top

hole position for wells drilled from the same platform. It is important that any wellbores where this

approach is adopted specify a valid “Slot Number” so that their well origins can be verified.

2.2.8 Bottom Hole Position

BOTHOLEYDD Bottom Hole Latitude

BOTHOLEXDD Bottom Hole Longitude

The position of the bottom hole is defined in terms of the longitude and latitude (in the selected

Geodetic Datum). This is expressed as a pair of real numbers (that is not using degrees minutes and

seconds).

It is possible (but fairly unlikely) that the bottom hole location could employ a different reference

system from the top hole location. Rule 16 checks for this (but delivers a note rather than an error).

2.2.9 Well Datum Type

Figure 9: Types of Well Datum

There are a restricted set of datum types that should be employed:

RT: Rotary Table

KB: Kelly Bushing

GLE: Ground Level Elevation (for on-shore wells)

Note that strictly speaking all on-shore wells should have both a “GROUND ELEVATION” value

and a well datum (for example the height of the Rotary Table or Kelly Bushing). However wells that

only provide an elevation above sea level will be allowed (providing the value makes sense in relation

to the other parameters).

Previous communications from DECC have suggested that Mean Sea Level (MSL) could also be

considered a valid well datum. This can no longer be accepted as the distance from Mean Sea Level

to Mean Sea Level should always be 0 (and hence provides no information about the well at all).

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2.2.10 Well Datum

This is the distance from a defined point to Mean Sea Level. Negative values indicate a datum below

Mean Sea Level. Measurements recorded in the wellbore are referenced from this point.

2.2.11 Water Depth/ Ground Elevation

GROUNDELEV Ground height above sea level (for on-shore wells)

WATERDEPTH Depth of water (for offshore wells)

This is the distance from mean sea level to either the seabed (for water depth) or ground level. In both

cases the normal direction is positive, that is water depth is positive downwards and ground level

positive upwards.

In addition to knowing the height of the well datum from mean sea level there are occasions when it is

valuable to understand the elevation of the ground (for onshore wells) or the depth of water (for

offshore wells).

Since each well can either be onshore (with a Ground Elevation) or offshore (with a Water Depth)

these two values should never both be set. The attribute that is inappropriate should have a blank

value (never a 0).

In some quadrants the depth of the sea floor or height of the land surface are fairly uniform. For

example in Quadrant 48 the seabed is between 10m and 55m below the surface, if a wellbore in this

quadrant claims to have a water depth of 107.9m it is reasonable to assume that there has been

confusion about units of measure and to return to the original records to check.

2.2.12 Driller’s TD

Figure 10: Measured Depth is from well datum, Vertical Depth is from mean sea level

The total depth of the well according to the driller, measured from the well datum as a distance along

the wellbore (‘MD’).

2.2.13 TVDSS – driller

Another key piece of information about the wellbore is the depth that the well was drilled to as a true

vertical depth from sea level (TVDSS).

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There is a point that is worth emphasising here. This parameter is the true vertical depth sub-sea; the

previous parameter (drillers TD) was the measured depth from the well datum. That means that the

following inequality must always be true:

TVDSS <= Drillers TD - Well Datum

It is common for there to be confusion between TVDSS and, for example TVDKB.

2.2.14 Spud Date

This is the date on which the well was first spudded. It may have a blank value for any well that is

planned but has not yet started drilling.

2.2.15 Date TD Reached

This is the date on which the total depth was reached. It may only have a blank value for a well that is

still currently drilling or where drilling has not yet started.

2.2.16 Completion date

This is the date on which the drilling was completed. The date a well is left in one of three

mechanical states following drilling:

Completed for Production - the date that perforation and setting of tubing and packers is

finished and the well is ready to produce

Abandoned - the date that the well bore, on completion of operations, is left in such a

condition that the open hole is plugged and sealed such that it may not be re-entered (in

general this will involve the cutting and retrieval of casing strings, removal of all drilling

mud and similar fluids, and permanent sealing of the wellhead with no components

remaining at surface)

Suspended (temporarily abandoned) - the day that the casing above the mud line is severed

following the setting of cement plugs.

Figure 11: The length of time between spud date and completion date for UK off-shore wells

There are a number of ways in which this date can obviously be seen to be incorrect. If it occurs

before the spud date, for example, however there are many wells whose dates seem unlikely without

being, strictly speaking, impossible. As Figure 11, above, illustrates the majority of wells in the North

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Sea are completed within 60 days of the Spud date. When a completion date is more than a year after

the spud date it is not necessarily incorrect, but it does hint that it should be checked.

2.2.17 Current Operator

If a well is not currently being operated it is acceptable to leave this attribute blank. Where a well’s

status is not “abandoned” then the operating company should be assigned a valid company name.

2.2.18 Original Well Intent

The original intent of the well, this is specified with a single letter code:

‘A’: Appraisal

‘E’: Exploration

‘D’: Development

2.2.19 Completion status

The completion status of the well can be one of:

‘PLANNED’: A well that has been planned but not yet started drilling

‘DRILLING’: A well that is being drilled at the moment

‘AB1’: The reservoir has been permanently isolated

‘AB2’: All intermediate zones with flow potential have been permanently isolated

‘AB3’: The well origin at surface is removed. The well will never be used or re-entered

again

‘COMPLETED_OPERATING’: Completed well that is currently active

‘COMPLETED_SHUT_IN’: Completed well that is shut in

‘PLUGGED’: A well that has been temporarily plugged

Abandoned Phase 1 requires that permanent barrier material is placed to fully isolate all reservoir

producing or injecting zones from the wellbore. The tubing may be left in place, partly or fully

retrieved.

Abandoned Phase 2 states that all intermediate zones with flow potential have been permanently

isolated. This may require the tubing to be partly retrieved if still present. Isolating liners, milling

and/or retrieving casing and setting cement or permanent barrier material to isolate intermediate

zones, with flow potential from each other and communication within the wellbore. The phase is

complete when no further permanent barriers are required.

An Abandoned Phase 3 occurs when the well is fully abandoned and the wellhead and conductor have

been removed. At this point the well will be removed from the well examination scheme. Phase 3

may include installing near-surface cement if required.

Because the code AB3 indicates that the wellhead has been removed it must apply to all the wellbores

associated with a single well origin. If one wellbore is AB3 then they must all be, conversely if one

wellbore is not AB3 then none of them can be.

In the names of the states COMPLETED_OPERATING and COMPLETED_SHUT_IN the word

“COMPLETED” is not strictly necessary since any well that is either shut in or operating must have

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been completed. However these values have been inherited from other sources and so the longer form

will continue to be employed to maintain compatibility.

2.2.20 Flow Class

The flow class specifies the fluids associated with the well:

CWGS: Condensate, water and gas shows

CWOS: Condensate, water and oil shows

DH: Dry Hole

GCS: Gas and condensate shows

GCW: Gas, condensate and water

GOCW: Gas, oil, condensate and water

GOW: Gas, oil and water

GS: Gas shows

GW: Gas and water

GWOS: Gas water and oil shows

HI: Hydrocarbon indicators

OCW: Oil, condensate and water

OGS: Oil and gas shows

OS: Oil Shows

OSCS: Oil shows and condensate shows

OW: Oil and water

OWCS: Oil, water and condensate shows

OWGS: Oil water and gas shows

UNKW: Unknown, the value has been searched for but cannot be found

2.2.21 Verification Company

This attribute lists the company that verified the CDA values. The name here is the CDA company

name so cannot be verified against either the OGA company list or the OGA company group list.

2.2.22 Verification Date

This is the date that the wellbore data was verified on within the CDA system.

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2.3 Optional Attributes

In addition to the mandatory attributes there are a number of optional ones that may also be populated.

NAME The well name

DEVTYPE The development type of the well

SLOTNO The slot employed (if it is a platform well)

PARENTROLE The role within the parent wellbore

PRIMARYTAR A code for the primary target

OTHERCLASS A well designation supplied for historical reasons

2.3.1 Wellbore Name

In addition to the OGA identifier there may be other names under which the wellbore is known. This

is a free text name so cannot be verified. It is most commonly employed for on-shore wells providing

the name of a nearby town or village to help identify the well.

2.3.2 Development Well Type

The “DEVTYPE” attribute indicates the type of development the well was intended for, for example

“Producer”, “Injector” or “Disposal”.

2.3.3 Slot Number

A free text description providing an identifier of the slot within the platform used to drill the well.

2.3.4 Parent Role

The intention of this attribute is to track the reason why a child borehole was created within its parent.

The current data has the following values:

REDRILL:

RESPUD:

SIDETRACK:

<Blank>: Well does not match one of the other values

2.3.5 Primary Target

This attribute is a free form text specifying the short code the operator employed to identify the

intended target of the wellbore.

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2.3.6 Other Class

In an older version of the system there was an attribute called “class” that controlled how the well was

drawn on a map. It was decided that this should be split into “Flow Class” which notes the fluids

associated with a well and “Other Class” that holds additional information. The values used here are:

JW: Junked Well

DR: Drilling

OBSW: Observation

RW: Relief Well

S: Suspended above TD

WDW: Water Disposal Well

2.3.7 Wellbore Path

The wellbore path is often provided in detail by listing points along the path in a separate file. These

usually take the form of an Azimuth survey (with values for “MDKB”, “Drift Angle” and “Azimuth

Angle” at each point) or an Offset path (with values for “MDKB”, “TVDSS”, “X Offset” and “Y

Offset” at each point). The Offset style is usually calculated from the Azimuth one by employing a

minimum curvature algorithm.

Because this is a distinct file it may be permitted to specify distances in metres or feet (International

Feet unless the unit is fully specified). In any case it is important to specify the units being employed

both for the distances and angles in the file. Whether the Azimuth angle is related to True North,

Magnetic North or Grid North must be clearly stated.

There is no support for this attribute in the current tool. In future versions this may be added.

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3 Quality Tests

This section will list textual descriptions of the various tests to be carried out on the wellbore data.

# Description Dimension Quality of

1 Must have valid COUNTRYCOD Consistent COUNTRYCOD

2 Must have valid QUADRANT Consistent QUADRANTNO

3 BLOCKNO must be 2 digits 01-30 Reasonable BLOCKNO

4 BLOCKSUFFI must be single lower case letter Consistent BLOCKSUFFI

5 PLATFORM must be single upper case letter or

empty

Consistent PLATFORM

6 DRILLSEQNO integer value > 0 Consistent DRILLSEQNO

7 WELLSUFFIX must be single upper case letter or

empty

Consistent WELLSUFFIX

8 DENNO must be a integer > 0 if the well is

offshore

Consistent DENNO

9 RESPONSIBLE_COMPANY must be valid

company group

Consistent RESPONSIBLE_

COMPANY

10 FIELD is either the string “NOT IN FIELD” or a

valid field name

Consistent FIELD

11 TOPHOLEYDD is a number between 48 and 64 Reasonable TOPHOLEYDD

12 TOPHOLEXDD is a number between -26 and 4 Reasonable TOPHOLEXDD

13 TOPHOLEYDD matches the QUADRANT Consistent TOPHOLEYDD

14 TOPHOLEXDD matches the QUADRANT Consistent TOPHOLEXDD

15 TOPHOLEDTM is “OSGB 1936” for land wells

and “ED 50” or “ETRS89” for offshore wells

Consistent TOPHOLEDTM

16 BOTHOLEDTM must match TOPHOLEDTM Consistent BOTHOLEDTM

17 BOTHOLEYDD is a number between 48 and 64 Reasonable BOTHOLEYDD

18 BOTHOLEXDD is a number between -26 and 4 Reasonable BOTHOLEXDD

19 BOTHOLEYDD matches the QUADRANT Consistent BOTHOLEYDD

20 BOTHOLEXDD matches the QUADRANT Consistent BOTHOLEXDD

21 Less than 30km distance from TOPHOLEYDD to

BOTHOLEYDD

Reasonable BOTHOLEYDD

22 Less than 30km distance from TOPHOLEXDD to

BOTHOLEXDD

Reasonable BOTHOLEXDD

23 DATUMTYPE is DF, RT or KB for offshore

wells and AGL, GLE, DF, RT or KB for onshore

ones

Consistent DATUMTYPE

24 DATUMELEV must be number greater than 0 Consistent DATUMELEV

25 If DATUMTYPE is DF, RT, KB or AGL value

should be below 300

Reasonable DATUMELEV

26 GROUNDELEV should be unset if the well is

offshore

Consistent GROUNDELEV

27 GROUNDELEV should be a number greater than

0 if the well is onshore

Consistent GROUNDELEV

28 WATERDEPTH should be unset if the well is

onshore

Consistent WATERDEPTH

29 WATERDEPTH should be a number greater than

0 if the well is offshore

Consistent WATERDEPTH

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# Description Dimension Quality of

30 WATERDEPTH should not exceed 4000 Reasonable WATERDEPTH

31 TOTALMDDRI should be a number greater than

0

Consistent TOTALMDDRI

32 TOTALMDDRI should be less than 10000 Reasonable TOTALMDDRI

33 TVDSSDRILL should be a number greater than 0 Consistent TVDSSDRILL

34 TVDSSDRILL should not be greater than

(TOTALMDDRI – DATUMELEV)

Reasonable TVDSSDRILL

35 LICENCE_NUMBER is a valid licence Consistent LICENCE_NUM

BER

36 OPERATOR is either empty string or valid

COMPANY

Consistent OPERATOR

37 The OPERATOR cannot be empty if the well

status (COMPLESTAT) is set to

“COMPLETED_OPERATING”

Reasonable OPERATOR

38 ORIGINTENT must be ‘A’, ‘E’ or ‘D’ Consistent ORIGINTENT

39 COMPLESTAT must be valid _STATUS Consistent COMPLESTAT

40 If the COMPLESTAT is “PLANNED” then the

SPUDDATE should be empty

Reasonable SPUDDATE

41 If the COMPLESTAT is not “PLANNED” then

the SPUDDATE should not be empty

Reasonable SPUDDATE

42 If the SPUDDATE is not empty it should have a

date after 1 Jan 1900 and before today

Reasonable SPUDDATE

43 If the COMPLESTAT is “PLANNED” or

“DRILLING” then the COMPLEDATE should be

empty

Reasonable COMPLEDATE

44 If the COMPLESTAT is neither “PLANNED” nor

“DRILLING” then the COMPLEDATE cannot be

empty

Reasonable COMPLEDATE

45 If the COMPLEDATE is not empty it should have

a date after the SPUDDATE and before today

Reasonable COMPLEDATE

46 If the COMPLEDATE is not empty then the

DATETDREAC should be between the

SPUDDATE and COMPLEDATE

Reasonable DATETDREAC

47 FLOWCLASS must be valid _FLOWCLASS Consistent FLOWCLASS

48 TOPHOLEYDD matches the BLOCK Consistent TOPHOLEYDD

49 TOPHOLEXDD matches the BLOCK Consistent TOPHOLEXDD

50 BOTHOLEYDD matches the BLOCK Consistent BOTHOLEYDD

51 BOTHOLEXDD matches the BLOCK Consistent BOTHOLEXDD

52 If the COMPLEDATE is not empty it should have

a date less than a year after the SPUDDATE

Reasonable COMPLEDATE

53 If the COMPLEDATE is not empty the

COMPLESTAT should not be “PLANNED” or

“DRILLING”

Reasonable COMPLEDATE

54 The WATERDEPTH should not be less than the

QUADRANT’s minimum (if defined)

Reasonable WATERDEPTH

55 The WATERDEPTH should not be greater than

the QUADRANT’s maximum (if defined)

Reasonable WATERDEPTH

56 The WELL_ORIGIN must be populated with a

valid wellbore name

Consistent WELL_ORIGIN

57 The WELL_ORIGIN should be in the currently

considered set of wellbores

Consistent WELL_ORIGIN

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# Description Dimension Quality of

58 Where the WELLREGNO is the same as

WELL_ORIGIN the WELLBORE_SEQUENCE

should be “WB1”

Reasonable WELLBORE_

SEQUENCE

59 When the WELLBORE_SEQUENCE is not

“WB1” the WELL_ORIGIN should be different

from the WELLREGNO

Reasonable WELL_ORIGIN

60 Where the WELLREGNO is not the same as

WELL_ORIGIN the WELLBORE_SEQUENCE

should not be “WB1”

Reasonable WELLBORE_

SEQUENCE

61 The WELLBORE_SEQUENCE contains the text

sequence "WB" followed by a positive integer

Consistent WELLBORE_

SEQUENCE

62 A development well must be associated with a real

field (i.e. the FIELD value cannot be “NOT IN

FIELD”)

Consistent FIELD

63 If the WELL_ORIGIN wellbore has a status of

"AB3" then this wellbore must have a status of

"AB3"

Consistent COMPLESTAT

64 If the WELL_ORIGIN wellbore has a status that is

not "AB3" then this wellbore cannot have a status

of "AB3"

Consistent COMPLESTAT

65 If the PLATFORM is defined the SLOTNO

should not be empty

Consistent SLOTNO

66 The WELL_ORIGIN wellbore should have a

DRILLSEQNO that is less than or equal to this

wellbore’s DRILLSEQNO

Consistent DRILLSEQNO

67 The DRILLSEQNO should match the final

number in the WELLREGNO

Consistent DRILLSEQNO

68 If the WELLSUFFIX is “R” or empty the

WELLREGNO ends in a digit otherwise the

WELLREGNO ends in the WELLSUFFIX

Consistent WELLSUFFIX

69 If the PLATFORM is not defined the SLOTNO

should be empty

Consistent SLOTNO

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4 Wellbore Validation Tool

The OGA has created a spreadsheet based tool to assist companies that are validating the wellbores.

This will be provided to each company pre-populated with: the current data they are responsible for;

software to carry out the tests; and some reports to illustrate progress.

Figure 12: Report of data quality in the OGA wellbore validation tool

In Figure 12 above, for example, the user can see which attributes have triggered most failures, which

rules have detected most issues and some overall measures of data quality and failure rates.

You should have been sent a version of this tool populated with just the wellbores that your company

is responsible for. The goal here is to revise the data in the “Wellbores” tab so that it represents the

correct values for all the wellbores. There are a number of tools and summaries to help you quickly

identify issues. A simple example will show the way these tools can be used.

If there are wellbores that you feel you have incorrectly been assigned responsibility for then you can

edit their “RESPONSIBLE_COMPANY” attribute to suggest which company group they should be

assigned to. Any wells where the “RESPONSIBLE_COMPANY” value does not match that shown

on the “Control” tab will be greyed out and the attribute values will not be checked. If you elect to

modify this attribute you must separately explain why these wells should be reassigned when you

return the data to the OGA.

The “Control” tab shows a number of displays that illustrate and track how the quality of the data is

improving. The attributes that are the most frequent cause of failures are indicated with the red bars

(in the case shown in Figure 12 the field name, bottom hole location and licence number all need to be

addressed). The rules table shows, for example, that Rule 10 is triggered frequently, the quality rules

(listed in Chapter 2.3.6 starting on page 20) show that this is a rule related to field names.

Pressing the “ReDo Checks” button will cause the tool to re-evaluate the current data and insert

highlights and comments into the “Wellbores” tab. Cells in that tab that are coloured in red indicate

25

attributes that have failed some tests, cells may also be coloured to indicate warnings, where values

that are apparently incorrect may be justified. Each coloured cell will also have a note attached to list

the rules that it has triggered, these can be reviewed by hovering the mouse cursor over the cell.

Figure 13: Two failures in the BOTHOLEXDD attribute

The blue ellipse in Figure 13 above shows where a longitude value is positive (while the

corresponding top hole location has a negative value). In addition the comment tells the user that the

value of -4.00007 (which is not a severe error but is worth checking) has failed rules 20 and 51.

Any of the cells in the “Wellbores” tab may be edited, so in the above case the value picked out by the

blue ellipse may be changed from a clearly incorrect positive value to its inverse. This value may also

be incorrect but it seems likely that a negative value of -3.49253 is going to be closer to the actual

value than the current one is. Of course in a real situation this value would need to be obtained from

other internal company systems or by examining the original drilling report.

When the data values in the Wellbores tab have been updated then activating the “ReDo Checks”

button will reprocess and highlight the current issues. After cycling through finding corrections,

editing the data and redoing the checks the summary numbers on the “Control” tab will show the

improvement to the quality that has resulted.

At any time activating the “Show Edits” button (also on the Control tab) will remove the formatting

that shows rule failures. The Wellbores tab will now highlight all the cells that have changed value

since the data was originally sent.

26

Figure 14: The “Show Edits” button shows what has been changed

In the illustration above all the cells with pale yellow backgrounds have been modified. This shows

not only where the well datum type has been changed (to “RT” and “KB”) but also where values of 0

in the ground elevation has been removed (being offshore wells a ground elevation of zero is

somewhat unlikely).

Once the data in the “Wellbores” tab has been edited to reflect your best understanding the

spreadsheet should be returned to OGA together with a descriptive note that confirms values for:

Your Company Group Name

The name of the person in your organisation who has approved the values

The position of that person

The data on which the values were deemed correct

A justification for any wellbores that should be assigned to a different company group

If there are any questions about the use of this tool, suggestions for how it could be improved, or

clarifications about the meanings of its terms then please contact OGA immediately, a list of names

and contact details has been provided on page 2 of this document.

27

4.1 The Overall Process

Figure 15: The overall process to correct the wellbore data

The company updates are the most important step in an overall process to improve the quality of the

wellbore data that OGA holds.

The overall process consists of the following steps:

Data Merge: obtaining the current OGA, CDA and other wellbore data and combining it

Select Data: identifying the data that is the responsibility of a particular company and

structuring it for correction

Adjust Data: within each company check any data issues against internal data resources

and correct the values

Checking: once corrections are submitted to OGA they are checked to ensure the returned

values are plausible

Updating Data: the modifications are finally applied to the OGA data and distributed to

other data sources

If you want to discuss any of these other stages in the overall process please contact any of the OGA

staff listed on page 2.

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4.2 Control Tab

Figure 16: Control tab in the wellbore quality checking tool

The initial tab provides a summary of the data quality issues. In addition to the two action buttons

that were explained in the previous section there are the following components:

Action Buttons: these two button process the “Wellbores” tab, the first does a quality

analysis, the second makes it easy to find values that have been modified locally

Overall Score: gives a summary indication of the overall quality score for this data. If the

data has no detected issues it would have a score equal to 100

Attribute Summary: provides an indicator for each attribute, the height of the red bars

shows the proportion of the wellbores that have issues detected for each attribute

Attribute Rates: shows the proportion of all attributes that failed or passed the tests

Wellbore Issues: shows the proportion of wellbores that had no issues, those with a single

attribute that failed and so on

Rule Summary: shows the rates at which each rule failed

Wellbore Issues: shows a graphical version of the wellbore issues data, the count of

wellbores which have no issues, just one failing attribute and so on

Original Attributes: provides the same type of display as the Attribute Summary but using

the original data. This is for comparison purposes against the current state

Rebuild Tests: certain operations of the “Wellbores” worksheet may disrupt the rule tests

(on the “Tests” worksheet). This button will rebuild the rules

29

4.2.1 Overall Score

The overall score provides a headline measure of the overall data quality. It is based on estimating the

average number of attributes with issues for each wellbore. The exact calculation is:

100*0.7(average number of attribute failures)

In a sense this can be seen as an arbitrary measure but it does allow a direct comparison of one set of

wellbore data with another and it provides an obvious indication of the impact that different data

corrections has. The metric is also deliberately structured to emphasise the impact of the type of

improvement gained when the data is approaching perfection. At that stage corrections are harder to

identify and they each impact fewer entities. In other words it is a better match for the effort required

rather than just the number of entities impacted.

This metric has the advantage that it does not depend on the absolute number of wells involved (so

can be used to compare well sets with radically different sizes). However it does depend on the exact

set of rules employed, each additional rule can only decrease the metric. This means that when

expressing this as a number one should strictly specify which rule set it is measured against. In

practice those that want to see a simple summary number usually don’t want to be exposed to the

complexities of how it is reached.

A number of different parameters were tried and these were chosen as the best reflection of previous

experience in data quality improvement projects.

4.3 Wellbores Tab

The second tab in the spreadsheet holds the current state of the wellbore data. Each row represents a

different wellbore, the columns showing the values of the attributes.

This tab can be in one of two “modes”. In results mode the majority of cells will have a pale yellow

background, other colours indicate cells that have triggered one or more quality rules:

Red Cells: indicate values that need to be corrected (failed rules)

Pink Cells: indicate values that are almost certainly wrong but possibly may be valid

(warned rules)

Orange Cells: indicate values that should be carefully checked, since they seem to be

invalid but may possibly be justified (noted rules)

In edit mode the majority of cells will have white backgrounds and pale grey text, any cell whose

value has been modified will have a yellow background and black text. This allows the user (and

OGA) to quickly identify the fixes that have been applied to the data.

4.3.1 Identifying wellbores with particular combinations of issues

One of the most frequent requirements is to focus only on wellbores that match a combined set of

conditions. Unfortunately there are too many potential combinations to easily build this type of

capability into the existing tool; however it is quite easy to exploit Excel’s capabilities to achieve this

type of result.

30

For example suppose we wanted to identify only the wellbores that passed Rule 29 but failed Rule 54.

There are clearly a number of ways to do this employing Excel’s inbuilt facilities, here is one method:

In the “Wellbores” tab find an unused column such as ‘AS’

Into the first wellbore cell in that column (cell ‘AS2’) enter the Excel formula

“=AND(OFFSET(Tests!$A$1,ROW()-1,29)=0, OFFSET(Tests!$A$1,ROW()-1,54)=9)”

Duplicate the ‘AS2’ cell to all the wellbore rows (a range like ‘AS3:AS450’)

Select the ‘AS’ column and filter on it (in the Data tab select the Filter command)

Select just the cells with a value of “TRUE”

Now only the wells that match the criteria will be shown. The fact that additional data has been

entered to the “Wellbores” tab will not cause any issues provided it is inserted beyond the range

supplied (in version 0.7.6 that would be beyond the ‘AS’ column).

This relies on the fact that the “Tests” tab has a cell for each test carried out on each wellbore. When

tests pass these cells have a value of 0, when they fail the cell will have a value of 9, or an error state

indicating the type of issue that was encountered.

4.4 Original Data Tab

This tab contains a record of the wellbore data before any fixes were applied. The contents of this tab

should not be modified at all.

Figure 17: The Original data shows the values originally supplied

This tab is colour coded to allow the user to see where this data originated from. Most of the data was

extracted from the OGA dataset and this is indicated by the cells with light blue text. A number of the

values were subsequently overwritten by those coming from CDA; these have been indicated using

the CDA colours (orange with dark blue text).

4.5 Rules Tab

This tab contains a list of the quality rules (and a summary of the results of applying them). The rules

listed here should be the same as those in Chapter 2.3.6 of this document.

31

4.6 Expect Attributes Tab

This tab lists the attributes that were catered for in this version of the tool. The attributes are listed

with some properties. There should be no reason for users to modify this tab.

4.7 Constants Tab

This tab contains a list of constants employed during the testing; this includes elements like the value

of Pi and radius of the Earth.

4.8 Tests and Summary Tabs

These two tabs hold intermediate results of the quality testing process. They can be helpful when

trying to track down individual issues.

The “Tests” tab has a column for each rule and a row for each wellbore. Each cell contains the

implementation of a single rule against a single wellbore. A value of 0 indicates where the rule has

passed and a 9 (or error) where a rule has failed.

4.9 Reference List Tabs

There are a number of reference list tabs that hold lists of valid values, for example lists of fields,

quadrant definitions, companies and so on.