when your mature environment is decline

8/14/2019 When Your Mature Environment is Decline

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trust us to see it differently.

Brownfields

When your mature environmentis in decline,


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Schlumberger is

an oilfield services

company supplying

technology, project

management, and

information solutions

to the E&P industry.

Executive summary

Typically in oil and gas production, the keenest interest and greatestinvestment is focused on the early life of a reservoirits productiveheyday. But times are changing. These days, brownfieldsdefinedas mature fields in a state of declining production or reaching the endof their productive lifeare regarded as potential fountains of youth.In an industry climate marked by growing demand, ever-greaterimportance is placed on enhancing and prolonging an asset's pro-

ductive maturity, maximizing its declining productivity, and postponingits demise.

Schlumberger has long recognized the need for cradle-to-grave technology; now, nearly 60% of the company's well services businessis channeled toward rejuvenating brownfields.

Author

Usman AhmedTheme manager, Brownfields

Contributors to this paper

Donna Garbutt, Lorne Simmons, Martin Isaacs, Leo Burdylo, Carl Trowell, and Karen GlaserSchlumberger

BrownfieldsWHITEPAPER


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Brownfields generally

re more than

0 years old and

ccount for 6772%

f world production.

One look at the World Energy Organization BasinExhaustion S-Curve brings the task of the explo-ration and production (E&P) industry into focus.

Brownfields, defined as mature fields in a state ofdeclining production or reaching the end of theirproductive lives, contain resources that are neededby producing countries and the world economy.These brownfields generally are more than 30 yearsold and account for 6772% of world production.When compared with other fieldsdeepwaterand greenfieldbrownfields represent the mostsignificant capacity to provide future production.

Headliner deepwater developments account foronly about 8% of global production, and greenfields(those fields under development, or producing and

perceived as having a high percentage of reservesstill in the ground) account for another 2025%.

While brownfields hold the majority of oil resources, the recovery factor is currently only about 3537%.This must be increased dramatically if we are to

achieve the 1.7% (11 million barrels of oil per day)growth in output needed to satisfy predicteddemand between now and 2010. So why are

we not seeing more recovered reserves frombrownfields?

The reasons are complex, as much driven byresource and portfolio decisions as by geologicalfactors. Many mature fields are being operatedusing technology put in place when the field wasoriginally developed. Technologies routinelyapplied in new field developments are beingignored in brownfields, and many of these fieldsare underperforming and require engineeringand operational attention. While increasing assetvalue through improved reservoir performancein such fields has been desired for decades,productivity and recovery results have beendifficult and even impossible to attain becausecritical tools and technologies were either notmade available or inadequate.

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Brownfields

Fig. 1. Potential causes of underperformance in previously stimulated wells. The GTI restimulation project team established a classification framework to help diagnose problems in hydraulically fractured wells that perform below operator expectations. At the highest level, there are three broad categories: ineffective or problematic initial completions, gradual production damage, and advances in technology or evolving techniques compared with past practices.

Wellunderperformance

Ineffective or problematicinitial completions

Unstimulated horizons Low fracture conductivity Short fracture length High skin, or damage

Outdated technology Advanced stimulation technology New completion techniques Well age

Gradual formation damageduring production

Scale and fines Workover frequency Well age


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Shouldering responsibility for brownfielddevelopmentSchlumberger experience has shown that improv-ing recovery from mature fields requires anapplication of practical and focused engineeringcoupled with the introduction of new technology.Most importantly, it requires specialization.

Schlumberger made a commitment 25 years ago to actively address brownfield challengesparticularly in the area of risk and cost reduction.That commitment remains true today.

For 75 years, our mission has been to tackleprojects in any area of the world. The requiredcollaboration between client and operator hasbrought about an expertise that translates well tobrownfields and a unique flexibility in technologyand in product development.

Fit-for-purpose technologies already developed orunder development offer ways to reach productiongoals and take efficiency in brownfields to newlevels. Current efforts to improve recovery ratesinvolve

better reservoir knowledge for understandingbypassed pay in existing fields and unrecov-ered oil in produced zones

real-time data delivery and decision systems

improved access to reservoirs

tailored technology, process offerings, andexpertise

full partnership capability and projectmanagement.

Short-term production goals are often achievedat the cost of high decline rates. Over the long term,a sustainable production plateau is sought. Thegreatest technology challenge is preparing for andenabling management of decline in the short termwhile increasing recovery factors in the longer term.

Managing production declineThe maturing fields in North America have taughtus that unlimited capital spending cannot reversedecline. While technology without expert directionand careful selection should not be considereda panacea, the technologies needed to slow,halt, or reverse production decline fall into thesecategories:

reevaluation of reservoir

remediation of wellbores and facilities

efficiently targeting bypassed or undevelopedreserves

production optimization, especially completionand lift strategies

fluid management in general, including watermanagement.

Many mature field

are being operated

using technology p

in place when the

field was originallydeveloped.

White Pa

Fig. 2. Current world production.

50

1

7

400

21

or ro uct on

(%)


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chlumberger made a

ommitment 25 years

go to actively

ddress brownfield

hallenges articularly in the

rea of risk and

ost reduction.

hat commitment

emains true today.

Reevaluationunderstanding the big pictureA key part of field reevaluation is to understand thecurrent state of production. A new, rigorous evalu-

ation to create a comprehensive reservoir modelis required and is accomplished by reevaluatingexisting data and gathering new data to recharac- terize the reservoir. Some fields are so old thatformation data are unavailable or sparse. In fieldswhere formation data are scant, identifying theremaining pay can be accomplished using newformation evaluation techniques to better under-stand the mechanisms at work in the reservoir.Advances in resistivity logging technology haveimproved cased hole formation evaluation andhave also demonstrated remarkable results in

detecting fluid behavior in declining reservoirs.A cased hole formation test tool with successrates in excess of 95% is being used to obtainmultiple samples in a single descent and to identifybypassed resources, such as oil swept to anotherpart of the reservoir as a result of waterflood.

Production logging technology is used to analyzecurrent well and reservoir production and identifyopportunities for improvement. At the scale of the field and the well, knowledge of individualperformance can help optimize production andmanage decline.

Looking to the future, todays greenfields are bene-fiting from real-time information, which is having asignificant impact on all technical areas and is

extending the peak of production. Customizedintelligent systems are helping optimize productivityfor tomorrows brownfields. Technology enhance-ments enable correct on-the-spot decisions andsolutions involving integrated cross-disciplinaryservices. Todays remote monitoring devices andinformation systems offer the option of understand-ing what is taking place in the reservoir and theability to take corrective action in real time.

Remediationinfill drilling andrecompletion

Reservoir management provides a better knowledgeof fluid distribution in the reservoir. This in turnmeans that highly effective well profiles can beplanned for infill drilling. Advanced imaging tech-niques allow the operator to select the bestlocations for infill drilling to optimize well placemenand to apply new cost-effective drilling methods.

Better steerability, improved dogleg capability, andslimmer tools have been developed to drill techni-cally difficult wells, e.g., complex trajectories tointersect as many target zones as possible or toreach one sweet spot.

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Brownfields

KdKf

Fig. 3. The frac-pack bypasses near-wellbore damage (Kd) and creates effective communication between the undamaged formation (Kf) and the wellbore.


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The greatest

technology

challenge is

preparing for

and enablingmanagement

of decline in

the short term

while increasing

recovery factors

in the longer term

White Pa

Specially designed seismic apparatuses are beingincorporated into new drilling technology to allowbetter formation imaging while drilling. The logging

suite delivers crucial real-time data for evaluating the positioning of drilling strings and modifying thewell path as needed.

Particularly useful in mature reservoirs in whichpressure has been a longstanding challenge is anew perforating system that controls an optimumdynamic underbalance reservoir pressure. New techniques minimize disruption of the cement-sandface hydraulic bond and create optimumperforation shape and length.

Productionbreakthroughs in fluids andfracturingInnovative technologiessmart matrix and fracturing stimulation fluids as well as next-generationdeployment methods like highly versatile coiled tubing (CT) fracturing unitsare being applied notonly to revive hydrocarbon production in maturefields, but also to develop greenfields with a view to efficient, longer-term production management.One of the key benefits of CT is that it fits inside the completion string, so precise deployment offracturing tools and fluids is possible at lower cost.

Selective treatments and smart placements arebecoming the techniques of choice. They aremaximizing acid coverage specific to each layerof a formation, increasing utilization of the fluid forgreater returns, often without mechanical inter-vention. One smart fluid is capable of pluggingwater zones while stimulating oil zones.

Use of various types of fracturing fluid has resultedin better control over fracture geometry by alteringviscosity without compromising the ability to trans-port proppant. This allows fracturing treatments tobe executed in producing zones close to water tables and with minimum stress differential.

Water managementboosting watered-down profitsIn brownfields, water handlingtreatment, trans-port, and disposal of recovered water; sale ofpotable water; or reinjection programscontinues to be addressed with great care. With the averageworldwide water cut estimated at 75% andincreasing, the issue of separating fluids at the

surface will be with the industry for the foreseeablefuture. Dealing with water is a costly fact of life inmost mature fields, with the average industry oper-ating expense at USD 0.50 per barrel of producedwater.

Pumping units and surface operations originallydesigned to handle oil and minimal water are nowproducing primarily water and only traces of oil.For example, California oilfields now operate on

the average at a water/oil ratio of 7:1. Disposallegislation regarding produced water is on theincrease worldwide.

Why is water such an overwhelming factor inbrownfields? Incompatible completions as a resultof production changes are one reason for theproblem. Increased water cut is related to reducedrecovery and surface facility bottlenecks. Also,historically, there has been a fragmented approach to water handling.

Fig. 4. Nonpolymer viscoelastic fracturing fluid.


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emaining zones of

ypassed oil often

equire complex well

ajectories that

ntersect as manyarget zones

s possible.

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Brownfields

The focus of future technology and processefforts will involve

downhole separation and disposal of water to reduce surface handling and to allowsurface facilities to process more oil

prevention of water entering the wellbore through the use of chemical or biologicalagents

integrated evaluation and engineeringprocesses to identify the type and locationof water breakthrough

improved reservoir energy management,including optimized water injection schemes,

water front prediction, and improved sweepefficiency.

Cost-effective solutions for decliningmarginsThe most recent developments in brownfield technology and software, coupled with projectmanagement expertise, help to mitigate therisks inherent in mature field portfolio additions.

In the mature field environment, integrating technology is critical to success. The challengesof declining production and a mature asset canbe met by altering the way reservoirs aredeveloped and managed from discovery throughdepletion and abandonmenttotal field lifecycle management.

From the first stimulation performed in 1932, itwas anticipated that production enhancement technology would have to evolve to align withfuture operator needs. Now, the need for operators to become more cost competitive is forginga stronger bond between operator and serviceprovider. Increasingly, operators are turning to

service companies to provide an integratedapproach to rehabilitating brownfields, bringingfocused engineering, technology, and manage-ment techniques to fields that have often beenneglected. This integrated project management(IPM) approach starts with a total reevaluationof the field in order to understand the fluid andpressure distribution of the reservoir; from this,an efficient and executable redevelopment planis derived and carried out.

The results can be significant when the right tech-nology and processes are applied. Our efforts torehabilitate brown fields are commonly undertaken

through a long-term alliance or partnership thatinvolves working with asset owners to achieveproduction or reserve goals. As an integratedservice company with a specialist projectmanagement group, we are able to apply fieldmanagement, well construction and intervention,and project and risk management skills to rehabili- tate brownfields in an integrated manner thatbrings together fit-for-purpose technology solutions.Each rehabilitation project is unique and tailored to match the objectives of the project and thegoals of the project owner.

When properly managed, a rehabilitation projectshould be guided by a clearly defined scope ofwork, a detailed project execution plan for han-dling all contingencies, and a planned ability tomanage change.

Often the first action in identifying which fieldshave the potential for major rehabilitation is toundertake a field optimization study (FOS) that willexamine the total field production operations with the objective of improving profitability throughidentifying opportunities for increased production,decreased costs, and improved water managementstrategies. From the FOS, an overall field redevel-opment plan can be engineered to implement thechanges necessary to revitalize the field. Fieldmanagement processes can be optimized byreal-time integration of new data into the fieldredevelopment plan and using simulation andeconomics tools to guide decision making.

Coaxing more oil from the reservoirBecause todays greenfields are tomorrowsbrownfields, the task of the service companyis to develop and cost-effectively deliver

better permeability data

better prediction of likely fracture geometry

better understanding of the reservoir

better integration of job planning, execution,and follow-up

more productive fields

better financial returns.


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Only a solid commitment to research anddevelopment and innovative thinking candeliver reservoir-focused applications and

effect positive change in efficient delivery ofwell services to drive down lifting costs andcoax more oil from the reservoir.

Enabling old fields to bounce backTechnology to economically restore productionin depleted reservoirs is being developed to address the complex issue of increasingproduction without adversely affecting thedecline curve.

During the past few years, a number ofSchlumberger technologies particularly appli-cable to further development of brownfields

have emerged. Some of these technologies,addressing all four areas of reservoir productionenhancement, include

ABC* Analysis Behind Casing services

Memory PS Platform * production services

PowerDrive* rotary steerable drilling systems

seismicVISION* logging while drilling tool

PURE* Perforating for Ultimate ReservoirExploitation system

PowerCLEAN* integrated system for effectivewellbore fill removal

OilSEEKER* acid diverter

VDA* Viscoelastic Diverting Acid

Innovative

technologies ... are

being applied not o

to revive hydrocarb

production in maturfields, but also to

develop greenfields

with a view to

efficient, longer-term

production

management.

White Pap

Fig. 5. Conventional and selective stimulations. Fracturing several zones grouped in large intervals, or stages,is a widely used technique. However, fluid diversion and proppant placement are problematic in discontinuous and heterogeneous formations. Conventional treatments, like this four-stage example, maximize fracture height, often at the expense of fracture length and complete interval coverage (left). Some zones remain untreated or may not be stimulated adequately; others are bypassed intentionally to ensure effective treat- ment of more permeable zones. Selective isolation and stimulation with coiled tubing, in this case nine stages,overcome these limitations, allowing engineers to design optimal fractures for each pay zone of a productiveinterval (right).

Stage Stage

Selectivefracture

stimulation

Conventionalfracture

stimulation

1 1

2

2

3

3

4

4

5

6

7

8

9

Optimalfracture length

Completeinterval coverage

Inadequatefracture length

Additional reservesMarginalpay zone

Insufficient intervalcoverage

Bypassedpay zone

PerforationsWellbore

FractureCasing

Additionalreserves


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he average

worldwide water

ut estimated is

t 75%.

ClearFRAC* surfactants

FloVIEW* holdup measurement tool

GHOST*

Gas Holdup Optical Sensor Tool RSTPro* Reservoir Saturation Tool for

PS Platform string.

Formation evaluation

ABC services allow complete formation evaluation through casing. Not only has this resistivity log-ging technology enabled cased hole formation

evaluation to gain in efficiency, it has alsorevealed remarkable results in detecting fluidbehavior in declining reservoirs.

The Memory PS Platform service, along with theFloView, GHOST, and RSTPro tools, is making adifference in the area of production logging.Memory PS platform measurements clearly identify entry points of oil and water into the wellborewith the same accuracy and quality as real-timeconfigurations in situations that preclude surfacereadout operation.

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Brownfields

Gamma Ray0 (gAPI) 50 Compressional

Coherence0 1 Shear

Coherence0 1

Standard processing

40 ( s/ft) 220

Casing-optimized processing

40 ( s/ft) 220

MD1 : 120

ft

X,X50

X,X60

X,X70

X,X80

X,X90

X,X00

X,X10

Fig. 6. Tools centered in the casing, low-frequency firing, and optimized transmitter-receiver tool spacing give ABC casing-optimized processing (right) better coherence and continuity than standard processing (left).


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Drilling and perforatingThe family of fully rotational PowerDrive systemsallows optimization of drilling from kickoff.Kicking off from vertical in an 181 4 to 171 2-in.hole to extended reach drilling to 8 1 2 in. or even53 4-in. hole is now possible. Drillstring sticking isreduced because there are no stationary com-ponents contacting the casing, whipstock, orborehole. Penetration rates are also improved,because there are no stationary components to create friction during operation.

Continuously updating the bit on the seismicmaps with seismicVISION logging while drillingcapabilities helps in

navigation

selecting casing and coring points

target depth prediction

reducing sidetracks and pilot holes.

Acquired interval velocities provide the datanecessary for managing pore pressure whiledrilling and optimizing mud weight.

Careful control of reservoir dynamics is critical to the success of the perforated completion.

Previous neglected variations in wellboreparameters have a profound effect on theperformance of the completion. By basing jobdesign on the properties of the reservoir, well-bore, and gunstring, the novel PURE techniqueconsistently minimizes or eliminates perforationdamage to maximize productivity.

The wellbore in many mature fields canbecome clogged by sand, silt (proppants),and other particles; keeping the perforationholes clear is an important step to improvingproduction. The PowerCLEAN solution uses aCT system to remove clutter in many challengingenvironments.

Stimulation and water controlOilSEEKER acid diverter for sandstones and car-bonates selectively plugs zones with high watersaturation. The acid enters the zones with highoil saturation. Use of this smart diverter makesmatrix stimulation easier and safer without thenitrogen used in foaming operations.

VDA fluid is based on unique Schlumbergerviscoelastic surfactant technology. Because itis polymer-free and self-diverting, the fluid canprevent formation damage while providing totalzonal coverage.

The ClearFRAC polymer-free fracturing fluid system was developed to provide maximum fractureconductivity as a result of minimum damageunder a range of conditions. Designed to operatewith significantly lower friction pressure whilepumping, this fluid has low hydraulic horsepower

requirements to reduce equipment demands. Bymaintaining a constant viscosity, the ClearFRACfluid offers a means to predict and control fracturegeometry.

In brownfields, corrective actions with the selection and application of intelligent technologiesand advanced methods in conjunction with reliable,verified data ultimately define project success,enabling fields that suffer from production falloff to make a comeback.

In the mature

field environment,

integrating

technology is

critical to success.

White Pa

Fig. 7. Depth control is paramount in fracturing through CT.


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OF_04_016_0

January 2004

Schlumberger

*Mark of Schlumberger

Todays brownfields have accounted for the majority of worldproduction, yet hold even greater potential for additional recov-ery. The way we see it, these mature, declining fields offer thegreatest promise for the future. Growing demand for energyand innovative recovery techniques means it pays to take asecond look at these potential wins.

Schlumberger Oilfield Services (OFS) brings you advanced tools and expertise to better understand the environment.

Advanced simulation software Cementing technology

Drilling services

Expert services

Formation evaluation tools

Information services

IPM

Multilateral completions

Perforating services

Stimulation technology

To learn more about

brownfields, visit

www.oilfield.slb.com/brownfield.

Technologyis key.

leads theway.Schlumberger

P d d b Oilfi ld M k i C i i H

when your mature environment is decline

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