Project Report --Water Shut Off

7/28/2019 Project Report --Water Shut Off

1/18

Page 1 of18

PROJECT REPORT ON

WATER SHUT OFF IN PRODUCTION WELLS

Under the guidance of Sri R K ANAND CE(P)

Submitted by:

1) Satish kumar duggi AEE(P)

2) Gautam kumar AEE(P)

3) Rajiv Sharma AEE(P)

4) Nizamuddin khan AEE(P)

5) Fasil PM AEE(P)

6) Siddharth Priya Nath AEE(P)

ON 07.06.2013

ONGC GT(I) -2013


2/18

Page 2 of18

ACKNOWLEDGEMENT

We would like to express our sincere gratitude to our supervisor RK

Anand CE(P),IOGPT, Oil & Natural Gas Corporation Limited, Panvel, Navi

Mumbai for his perceptive suggestions and comments that helped us to

remain motivated and enthused in completing this work. He has provided

various facilities during the course of this project work. His infallible

supervision and guidance has made this work a more rewarding

experience for me.

I would like to thanks to Mr. & other library assistant for

cooperating during my project work.

We would like to thank to all the employees and staff members who

have contributed directly or indirectly in successful completion of ourproject work.


3/18

Page 3 of18

INDEX

CONTENTS PAGE NO

1. Abstract 42. Introduction 53. Water sources4. Water problems5. Candidate well selection6. Diagnostic Methods7. Water control Technologies8. Post Job Evaluation & Success criteria


4/18

Page 4 of18

ABSTRACT

This project report draws attention towards water problems in oil &

gas reservoirs due to multiple reasons. Selection of candidate wells for

water problems and their proper diagnostics has been detailed out.

Accordingly the proper water shut off job and treatment techniques

has been explained to fix the water problem in the wells . A number of

new technologies have been put to explain the development going on

in the field of excessive water problem & their countermeasures.


5/18

Page 5 of18

INTRODUCTION

Excessive water production causes major economic problems in terms of

loss of oil production, as well as lifting, separating and disposing of largeamounts of wastewaters. In addition, water production causes scale,

corrosion and emulsion problems, major environmental

problems.Therefore, every effort should be made to minimize excessive

water production. Produced water can be reduced or avoided by using

mechanical or chemical means. Mechanical means include drilling

horizontal wells, placing a liner then perforating the target zone, or using

downhole separation equipment, e.g., a hydrocyclone.

Another problem that is caused by the presence of high permeability

zones is differential pressure sticking, which occurs during drilling across

porous and permeable formations. Differential pressure sticking occurs

when the drill pipe becomes stuck in the filter cake on a permeable

formation during drilling , mud and filtrate are lost into permeable zones

when the mud hydrostatic pressure in the wellbore, Ph, is greater than

the formation pore pressure, P. As the filtrate is lost, the solids in the mud

are deposited on the formation face as filter cake. The characteristics of

the filter cake depend on the type and amount of solids present in the

mud. A mud with high native solids content leaves a thick sticky filter

cake, while a mud with bentonite produces a slick thin filter cake.

Selection of a specific water shut-off treatment depends on the sources

of water, which include: coning, casing leaks, high permeability streaks,

and natural fractures. Understanding reservoir characteristics and watermovement in the reservoir are key factors that determine the success of

these treatments.


6/18

Page 6 of18

WATER SOURCES

Water is present in every oil field and is the most abundant fluid in the

field.No operator wants to produce water, but some waters are betterthan others. When it comes to producing oil, a key issue is the distinction

between sweep, good (or acceptable), and bad (or excess) water.

Sweep waterSweep water comes from either an injection well or an

active aquifer that is contributing to the sweeping of oil from the

reservoir. The management of this water is a vital part of reservoir

management and a determining factor in well productivity and theultimate reserves.

Good waterThis is water that is produced into the wellbore at a rate

below WOR economic limit. It is an inevitable consequence of water

flow through the reservoir, and it cannot be shut off without losing

reserves. Good-water production occurs when the flow of oil and water

is commingled through the formation matrix. The formation water flow is

dictated by the natural mixing behaviour that gradually increases the

WOR .

Bad waterBad water can be defined as water that is produced into

the wellbore and produces no oil or insufficient oil to pay for the cost of

handling the waterwater that is produced above the WOR economic

limit. In individual wells, the source of most bad-water problems can be

classified as one of ten basic types. The classification of water problem

types presented here is simplisticmany variations and combinations can

occurbut it is useful for providing a common terminology.


7/18

Page 7 of18

WATER PROBEMS

Casing, tubing or packer leaksLeaks through casing, tubing or packers

allow water from non- oil-productive zones to enter the productionstring. Detection of problems and application of solutions are highly

dependent on the well configuration. Basic production logs such as fluid

density, temperature and spinner may be sufficient to diagnose these

problems. In more complex wells, WFL Water Flow Logs or multiphase

fluid logging such as the TPHL three-phase fluid holdup log can be

valuable. Tools with electrical probes, such as the FlowView tool, can

identify small amounts of water in the production flow. Solutions typically

include squeezing shutoff fluids and mechanical shutoff using plugs,

cement and packers. Patches can also be used. This problem type is a

prime candidate for low-cost, inside-casing water shutoff technology.

Channel flow behind casingFailed primary cementing can connect

water-bearing zones to the pay zone (below middle). These channels

allow water to flow behind casing in the annulus. A secondary cause is

the creation of a void behind the casing as sand is produced.

Temperature logs or oxygen-activation-based WFL logs can detect this

water flow. The main solution is the use of shutoff fluids, which may be

either high-strength squeeze cement, resin-based fluids placed in the

annulus, or lower strength gel-based fluids placed in the formation to

stop flow into the annulus. Placement is critical and typically is achieved

with coiled tubing.

Moving oil-water contactA uniform oil- water contact moving up into

a perforated zone in a well during normal water-driven production can

lead to unwanted water production (below right). This happens wherever

there is very low vertical permeability. Since the flow area is large and the

rate at which the contact rises is low, it can even occur at extremely low

intrinsic vertical permeabilities (less than 0.01 mD). In wells with higher


8/18

Page 8 of18

vertical permeability (Kv > 0.01 Kh), coning and other problems

discussed below are more likely. In fact, this problem type could be

considered a subset of coning, but the coning tendency is so low that

near-wellbore shutoff is effective. Diagnosis cannot be based solely onknown entry of water at the bottom of the well, since other problems

also cause this behavior. In a vertical well, this problem can be solved

easily by aban- doning the well from the bottom using a mechanical

system such as a cement plug or bridge plug set on wireline. Retreatment

is required if the OWC moves significantly past the top of the plug.

Watered-out layer without crossflowA common problem withmultilayer production occurs when a high-permeability zone with a flow

barrier (such as a shale bed) above and below is watered out (above). In

this case, the water source may be from an active aquifer or a waterflood

injection well. The watered-out layer typically has the highest

permeability. In the absence of reservoir crossflow, this problem is

easily solved by the application of rigid, shutoff fluids or mechanical

shutoff in either the injector or producer. Choosing between placement

of a shutoff fluidtypically using coiled tubingor a mechanical shutoff

system depends on knowing which interval is watered out. Effective

selective fluids, discussed later, can be used in this case to avoid the cost

of logging and selective placement. The absence of crossflow is

dependent on the continuity of the permeability barrier.

Horizontal wells that are completed in just one layer are not subject to

this type of problem. Water problems in highly inclined wells completed

in multiple layers can be treated in the same way as vertical wells.

Coning or cuspingConing occurs in a vertical well when there is an

OWC near perforations in a formation with a relatively high vertical per-

meability (below). The maximum rate at which oil can be produced

without producing water through a cone, called the critical coning rate, is


9/18

Page 9 of18

often too low to be economic. One approach, which is sometimes

inappropriately proposed, is to place a layer of gel above the equilibrium

OWC. However, this will rarely stop coning and requires a large volume

of gel to significantly reduce the WOR. For example, to double the crit-ical coning rate, an effective gel radius of at least

50 feet [15 m] typically is required. However, eco- nomically placing gel

this deep into the formation is difficult. Smaller volume treatments

usually result in rapid water re-breakthrough unless the gel fortuitously

connects with shale streaks.

A good alternative to gel placement is to drill one or more lateral

drainholes near the top of the formation to take advantage of the greater

dis- tance from the OWC and decreased drawdown, both of which reduce

the coning effect.

In horizontal wells, this problem may be referred to as duning or

cusping. In such wells, it may be possible to at least retard cusping with

near-wellbore shutoff that extends sufficiently up- and downhole as in

the case of a rising OWC.

Fractures or faults between injector and producerIn naturally

fractured formations under waterflood, injection water can rapidly

break through into producing wells (above). This is especially common

when the fracture system is extensive or fissured and can be confirmed

with the use of interwell tracers and pressure transient testing.6 Tracerlogs also can be used to quantify the fracture volume, which is used for

the treatment design. The injection of a flowing gel at the injector can

reduce water production without adversely affecting oil production from

the formation. When crosslinked flowing gels are used, they can be

bullheaded since they have limited penetration in the matrix and so selec-

tively flow in the fractures. Water shutoff is usually the best solution for

this problem.


10/18

Page 10 of18

Wells with severe fractures or faults often exhibit extreme loss of drilling

fluids. If a conductive fault and associated fractures are expected during

drilling, pumping flowing gel into the well may help solve both the drilling

problem and the subsequent water production and poor sweepproblemsparticularly in formations with low matrix permeability.

In horizontal wells, the same problem can exist when the well intersects

one or more faults that are conductive or have associated conductive

fractures.

Fractures or faults from a water layer Water can be produced from

fractures that intersect a deeper water zone . These fractures may be

treated with a flowing gel; this is particularly successful where the

fractures do not contribute to oil production. Treatment volumes must be

large enough to shut off the fractures far away from the well.

However, the design engineer is faced with three difficulties. First, the

treatment volume is difficult to determine because the fracture volume is

unknown. Second, the treatment may shut off oil-producing fractures;

here, an overflush treatment maintains productivity near the wellbore.

Third, if a flowing gel is used, it must be carefully tailored to resist

flowback after the treatment. In cases of localized fractures, it may be

appropriate to shut them off near the wellbore, especially if the well is

cased and cemented. Similarly, a degradation in production is caused

when hydraulic fractures penetrate a water layer. However, in such

cases the problem and environ- ment are usually better understood and

solutions, such as shutoff fluids, are easier to apply.

In many carbonate reservoirs, the fractures are generally steep and tend

to occur in clusters that are spaced at large distances from each other

especially in tight dolomitic zones. Thus, the probability of these fractures

intersecting a vertical wellbore is low. However, these fractures are often

observed in horizontal wells where water production is often through


11/18

Page 11 of18

conductive faults or fractures that intersect an aquifer. As discussed

above, pumping flowing gel may help address this problem.

CANDIDATE WELL SELECTION

Recovery plotThe recovery plot is a semilog plot of WOR against

cumulative oil production (above). The production trend can be ex-

trapolated to the WOR economic limit to determine the oil

production that will be achieved if no water-control action is taken. Ifthe extrapolated production is approximately equal to the expected

reserves for a well, then the well is producing acceptable water and no

water control is needed. If this value is much less than the expected

recoverable reserves,the well is producing unacceptable water and

remedial action should be considered.

Production history plotThis plot is a log-log plot of oil and water rates

against time (below left). Good candidates for water control usually show

an increase in water production and a decrease in oil production starting

at about the same time.

Decline-curve analysisThis is a semilog plot of oil production rate

versus cumulative oil. A straight line can be expected for normal

depletion. Any sudden change in the slope of the usual straight-line

decline in oil production rate is a warning that excess water, as well as

other problems, may be affecting normal production.


12/18

Page 12 of18

DIAGNOSTIC METHODS

The key to water control is diagnosticsto identify the specific water

problem at hand. Well diagnostics are used in three ways:

to screen wells that are suitable candidates for water control

to determine the water problem so that a suitable water-control

method can be selected

to locate the water entry point in the well so that a treatment can be

correctly placed.

A diagnostic log-log plot of WOR versus time can be used to help deter-

mine the specific problem type by making comparisons with known

behavior patterns (left). Three basic signatures distinguish between dif-

ferent water breakthrough mechanisms: open flow through faults,

fractures, or channel flow behind casing; edgewater flow or a moving

OWC; and coning problems.7 Edgewater flow interpre- tations have

been constructed from numerical simulation and field experience.8

The time- derivative of the WOR also can be used, but the uncertainty or

noisy nature of field measure- ments generally limits its application. The

inter- pretation engineer can learn to recognize the many variations in

these profiles and minimize the problem of nonuniqueness, when

combined with other data.

The usefulness of WOR diagnostic plots in determining multilayer water

encroachment is illustrated by an example in a field operated by a major

North Sea operating company. A medium- size reservoir with a

moderate-to-high energy shoreface structure had been heavily

bioturbated, giving rise to substantial permeability variations (next page,

top). No significant shale barriers were present, and the 360-ft [110-m]

thick reservoir from X590 to X950 ft [X180 to X290 m] gently dipped intoan aquifer. The edges of the reservoir were bounded by sealing faults and


13/18

Page 13 of18

truncated by an unconformity. A vertical well was perforated across 165

ft [50 m] in the middle of this unit. No OWC or gas-oil contacts (GOC)

were present in the reservoir.

The WOR-diagnostic plot generated from monthly well-test data shows

the effect of the permeability variation in the reservoir strata (next

page, bottom). The plot illustrates watering-out of high-permeability

layers, which contribute to crossflow in the reservoir. The ratio of

breakthrough times (1800:2400:2800) gives an indication of the

permeability ratios in these layers. The cumulative oil produced and the

relative permeability-height products of the layers might be used toestimate the remaining reserves in the lower permeability parts of the

formation.


14/18

Page 14 of18

Water-Control Technologies

Each problem type has solution options that range from the simple and

relatively inexpensive mechanical and chemical solutions, to the morecomplex and expensive reworked completion solutions. Multiple water-

control problems are common, and often a combination of solutions

may be required. Today, in addition to the traditional solutions described

above, there are new, innovative and cost-effective solutions for water-

control problems.

Mechanical solutionsIn many near- wellbore problems, such ascasing leaks, flow behind casing, rising bottom water and watered- out

layers without crossflow, mechanical or inflatable plugs are often the

solution of choice. The PosiSet mechanical plugback tool can be

deployed on coiled tubing or wireline, and is a field-proven technology

that ensures reliable wellbore shutoff in cased- and openhole environ-

ments (right).

When the wellbore must be kept open to levels deeper than the point of

water entry, a through-tubing patch may be the answer. For example, a

new coiled tubing- or wireline- deployed, inside-casing patch called the

PatchFlex sleeve has been used successfully in many applications

worldwide (far right). It is particularly well suited to through-tubing water

or gas shutoff, injection-profile modifications and zonal isolation. The

inflatable sleeves are custom-built to match the length of the perforatedintervals and can withstand wellbore crossflow pressures. Once set, the

sleeve becomes a composite liner inside the casing that is millable using

through-tubing techniques if a subsequent squeeze operation is

desired, or it can be reperforated later to allow reentry to the zones. The

only disadvantage of the composite liner is a reduction of less than 1 in.

[2.5 cm] in the wellbore diameter. However, other mechanical patch

remedies take up even more of the available casing inner diameter.


15/18

Page 15 of18

Chemical solutionsChemical treatments require accurate fluid

placement. Coiled tubing with inflatable packers can help place most

treatment fluids in the target zone without risk to oil zones. Coiled

tubing dual injection is a process of pumping protective fluid down thecoiled tubing to the casing annulus and delivering the treatment fluid

through the coiled tubing (right).

SqueezeCRETE cement is another key weapon in the armory of

water-control solutions.17 Its low fluid loss and capability to pene-

trate microfractures narrower than 160 microns make it ideal for

remedial treatment of tubing leaks caused by flow behind pipe. Onceset, this cement shows high compressive strength, low permeability and

high resistance to chemical attack. SqueezeCRETE treatment is often

used with common cement for shutting off perforations when the

problem is watered-out layers, or rising bottom water or OWCs. Other

applications include sealing gravel packs, casing leaks or channels behind

casing.

Rigid gels are highly effective for near- wellbore shutoff of excess water

(right). Unlike cement, gels can be squeezed into the target formation to

give complete shutoff of that zone or to reach shale barriers. They have

an operational advantage over cement treatments because they can be

jetted rather than drilled out of the well-bore. Typically based on cross-

linked polymers, products like MaraSEAL and OrganoSEAL-R systems can

be easily mixed and have a long working life. They can be bullheaded into

the formation to treat specific water problems such as flow behind casing

and watered-out layers with-out crossflow, or selectively placed in the

water zone using coiled tubing and a packer.18

Another solution is a flowing gel that can be injected into small faults or

fractures, but only penetrates formations with permeabilities greater

than 5 darcies. Large volumes (1000 to 10,000 bbl) [159 to 1589 m3] of


16/18

Page 16 of18

these inexpensive fluids often successfully shut off extensive fracture

systems surrounding waterflood injector or producing wells.19 Like rigid

gels, products such as Marcit and OrganoSEAL-F systems are cross-linked

polymers that are simple to mix, have a long (up to three days) workingtime before becoming rigid, and can be pumped through completion

screens.

Smart or selective fluids in the form of polymers and surfactants are

being developed for formation matrix treatments near the wellbore.

These treatments, called relative permeability modifiers, produce a

permanent gel-like material to stop flow in water layers, but retain fluidbehaviour in oil layers to allow production to continue.


17/18

Page 17 of18

POST JOB EVALUATION

Justification of a treatment in any well is based on the value of the

increased hydrocarbon production expected. The key word hereisexpected, which indicates a degree of uncertainty in the analysis. Some

water-control treatments can guarantee substantial production

increase. In such circumstances, the primary element of uncertainty is

the job success itself. When the incremental production is relatively small

(or was based on several assumptions) not only does job-risk come into

play, but also the prediction itself becomes a key risk. Therefore, the

value of a water- control treatment to the operator needs to be quan-

tified. An analysis incorporating the multifaceted components of risk can

be undertaken using the methods of quantitative risk analysis.

Status Oil Production Water Production

Technical SuccessIncreases Unchanged

Unchanged Reduces

Economic Success

Sustained increase

equivalent to 10

times the cost of job

Increases

Decrease

Unchanged

Economic &

Technical Success

Sustained increase

equivalent to 10

times the cost of job

Decrease


18/18

Page 18 of18

BIBLIOGRAPHY

1. www.wikipedia.org

2. www.petroone.org

3.

Documents

Project Report --Water Shut Off