Scale ManagementTechnologies and techniques that protect your

production from the reservoir to the surface

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The M-I SWACO Scale-Management SystemOur system for managing scale in your wells encompasses the complete cycle of scale control, including:

Identifying a problem

Identifying a solution

Prescreening and laboratory qualification of suitable products

Offshore qualification and optimization

Follow-up

Re-evaluate the treatment and start the process at the beginning, if necessary

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M-I SWACO gives you control over scale because we understand how it works

The first step in creating an effectivescale-management program is tothoroughly understand the scaleformation mechanism, the well/ formation environment and theoptions available for treatment. With this methodology as a guide,M-I SWACO* has designed an effective scale-managementstrategy that considers:

• Why mineral scales are formed, howthey are deposited and how thesedeposits can grow

• Predictions of when and where scalewill be formed

• Evaluations of the various potentialinhibitor chemicals, including thosethat can be modified or developedfor a particular situation

• The techniques required to success-fully deploy the inhibitors andensure their continued effectiveness

• Options for scale removal wheneither inhibition has not been used or the strategy applied has not been successful

Our prescreening processidentifies where problems are likely to occurBased on available data from the wellor process system, we use computer-simulation software, such as Petrotech’sMultiScale^ package, to predict andevaluate scale potential and risk. Ourhighly trained and knowledgeablepersonnel assess the results, which arethen used to evaluate scale potentialand the process environment. Thisevalua tion becomes the basis for achemi cal screening and the selectionof products for laboratory testing.

Meeting your criteria is at theheart of our laboratory and field evaluation processesOur all-inclusive portfolio of environ-mentally acceptable scale inhibitorsand treatment methods is a result ofone of the industry’s most extensive

laboratory evaluation programs.Products selected from our pre-screening process undergo laboratoryevaluation based on the customer’scriteria for deploying chemical treat-ment. Our technical-service scale lab-oratories in Aberdeen and Bergenhave the expertise and tools to carryout all tests required for qualifying asuitable product package, including:

• Static prescreening test for compati-bility, efficiency and adsorption

• Dynamic tube-blocking tests both atHigh-Temperature, High-Pressure(HTHP) and Low-Temperature, Low-Pressure (LTLP) for determination of injection dosage or minimuminhibitor (“threshold”) concentration

• Core flood to simulate scaleTo enhance the process, we employ

specialized, proprietary software thatpredicts the occurrence, location andseverity of potential scale problems.

Scaleprecipitatedmg/L

Formation waterNa 50000Ca 3000Ba 300Sr 700HCO3 1000SO4 0

SeawaterNa 12000Ca 350Ba 0Sr 5HCO3 150SO4 2750

CaCO3

BaSO4

SrSO4

100

100%FW 100%SW50:50

The emphasis we place on pro -viding “total service” is reflected inour onsite performance evaluationsthat employ a unique dynamic scaletest rig to ensure our products’ per-formance in the field is consistentwith what we have observed inlaboratory evaluations.

We prove our products’environmental compliance for every applicationBefore any product can be used in the field it must first be approvedby the M-I SWACO GLP-approvedecotoxicological laboratory in Bergen.This laboratory ensures that all pro-posed products comply with eachcountry’s environmental require-ments. We perform a variety ofecotoxicological tests, includingbiodegradation (OECD 306), bio -accumulation (OECD 117, 107) and toxicity testing.

All of the most widely used chemi-cal types of scale inhibitors exhibitrelatively low toxicity in the marineenvironment and do not tend tobioaccumulate. Yet, because of theirvery low level of biodegradability,these chemicals have a high persist-ence. In response to the demands of the industry, M-I SWACO now supplies a number of new polymericand phosphorus-containing scaleinhibitors to meet the industry’sdemands for more environmentallyacceptable scale-control chemicals.

Innovative scale-inhibitiontechnologies for the mostdemanding conditionsDue to increasingly complicated wellcompletions, production from harshenvironments such as HTHP anddeep water fields, and stricter environ-mental regulations, we have investedheavily in the development of newscale-control technology. The result ofthat investment is a comprehensiveline of scale-inhibitor chemistries and

deployment techniques, focusing onthree niche areas:

a. Continuous scale-inhibitor injection via gas-lift system

b. Preemptive squeezing of reservoirs using non-aqueous-base scale inhibitors

c. End-capped polymeric scale inhibitors

Gas-lift scale inhibitionDeploying scale inhibitors via gas liftis a cost-effective means of managingscale formation within the productiontubing. M-I SWACO has developed arange of gas-lift scale inhibitors thatcan be customized for any scaling

By reproducing conditions within the annulus and gas-lift valve, M-I SWACO is able to assess the injection-gas-to-scale-inhibitor ratio that is likely to cause gunking.

OFN gassupply

Flow meter

1-way flowvalve

PRV

Pump

SI

Heatingcoil, SI

SI bleedline

Abs. Pinlet

Abs. Poutlet

PC(logging)

DPT

Heatingcoil, OFN

Micro-bore“test” coil

Needlevalves

Oven Outletsample

collectionvessel

Samplingvalve

Pressure-control valve

PCV

Injection well

Co-mingling

Gas

Water

Oil

Incompatible formation water and injectionwater co-mingle. Sulphate scale forms as a resultof change in water composition.

Continuous wellhead additionscale inhibitor Gas

Oil export to refinerySeparator

Heater

Productionwellhead

Annulus/gas lift injection

Scale-squeeze inhibitors

Solid-scale inhibitors

Rat-hole Horizontalsection

Waterinjection

InjectionwellInjection

water

Formationwater

OilReservoir

Flotation Lagoon,buffertank Filter

regime. These products have beenfully assessed for inhibition and eval-uated using a technique that exam-ines performance under dynamicconditions. The evaluation replicatesthe actual flow regimes and gas-to-scale-inhibitor mixing ratios atcritical points within the system,including the annulus, gas-lift valveand sump.

Our cutting-edge gas-lift scaleinhibitors all exhibit four keycharacteristics:

• Acceptable environmentalproperties

• Viscosity of <20 cP as supplied and after any volatile loss

• Corrosivity of <0.1 mm/yr

• Compatible with a wide range of brine compositions, includinghigh calcium

Preemptive squeezing with non-aqueous-base scale inhibitorsIn recent years M-I SWACO has conducted extensive research onidentifying scale-inhibitor chemis -tries and deploying techniques forsqueezing, using non-aqueous-basescale inhibitors. Regardless of thechemistry or the means of deliveringthe chemical into the near wellbore,the reasons for the development ofnon-aqueous-base scale inhibitorshave been twofold:

• The desire for scale protection prior to a well cutting water

• The ability to squeeze scale inhibitorinto a water-sensitive reservoirwithout causing formation damageNon-aqueous-base scale inhibitors

are required for wells where severescaling is predicted at the onset ofwater production or for unmannedplatforms where the mobilizationtime can be so lengthy that it puts theasset at risk. Additionally, reservoirscontaining illitic or smectitic clays aresensitive to the application of aqueous-base scale-inhibitor treatments.

Many operators now consider preemptive treatment with a non-aqueous-base scale-inhibitor packagean essential requirement of their totalscale-management strategy. Regard lessof the severity of scaling at the onsetof water production, a non-aqueous-base treatment prevents scale for -mation and protects asset value.

M-I SWACO has developed arange of non-aqueous-base scaleinhibitors that has been independ-ently assessed as “Best-in-Class” andsuperior to those of our competitors.In the field, squeezes with our non-aqueous-base treatment packagehave delivered signif icant increasesin oil productivity. Key featuresof our non-aqueous-base scaleinhibitors are:

• Customizable to any scaling regime

• Eliminate the tendency for emulsion formation

• Proven field results

• Stimulate oil production after squeezing

We deliver a scale-squeezedesign tailored to your project

M-I SWACO designs scale-squeeze

treatments based on the specific

information available for each well,

inhibitor properties determined in

the laboratory and computer simu-

lation tools such as SQUEEZEVI*. In

cooperation with the customer, the

treatment and placement can then

be optimized using well and near-

well reservoir models.

This graph illustrates test conditions mimicking those expected within the annulus. As shown, all con -ditions examined revealed no differential-pressure increase, thereby preventing the formation of gunk.

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100 150 200 250 300 350 400 450 500 550 600

Injection time, min

Dif

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ress

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, psi

OFN = 1.0 L/min

SI = 0 SI =1.0 mL/minDP ~ 41 psi

SI = 0.5mL/min

DP ~ 33 psi

SI = 0.25 mL/minDP ~ 30 psi

Injectioncontinued over

20 hrs

OFN

cyl

ind

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han

ged

OFN =1 L/min

A battery of tests in the laboratory ensures positive results in the fieldProducts selected from prescreening

undergo laboratory evaluation based

on the customer’s criteria for deploying

chemical treatment. Our technical- service

scale lab ora tories in Aberdeen and Bergen

have the expertise and tools to carry out

all tests required for qualifying a suitable

product package including:

• Static prescreening test for com patibility,

efficiency and adsorption

• Dynamic tube-blocking tests both at

High-Temperature, High-Pressure (HTHP)

and Low-Temperature, Low-Pressure

(LTLP) for determination of injection

dosage or minimum inhibitor

(“threshold”) concentration

• Core flood to simulate scale

Scale-inhibitor static testsStatic beaker (bottle) tests have become

an industry-recognized standard, used

routinely to assist with the performance

evaluation of scale-inhibitor products.

M-I SWACO per forms static beaker tests —

including inhibitor efficiency, adsorption,

compatibility and thermal stability — as

the first round of inhibitor screening.

Inhibitor compatibility test: Interactions

between inhibitor species and multivalent

ions in the brine can cause incompatibility

problems in the field of application. In

particular, the formation of inhib itor/Ca2+

complex can lead to a precipitation. If such

a complex forms in the near-wellbore area,

it could result in formation damage. These

tests are carried out by visual observations

to an inhibitor sample at a given pH,

temperature and brine chemistry.

Inhibitor adsorption and thermal

stability tests: Both test pro cedures are

frequently performed in the M-I SWACO

scale laboratory. The maximum temper -

ature at which to safely conduct these

tests is 203° F (95° C).

Scale-inhibitor dynamic testsScaling-loop tests evaluate the effi ciency

of chemical inhibitors and are carried

out under dynamic conditions to more

closely simu late actual field conditions.

M-I SWACO has installed a custom-built

HTHP tube-blocking rig to enable us

to conduct large-scale screening of

scale inhibitors across a wide range

of conditions.

The tube-blocking rig is comprised of:

• HPLC piston pumps

• A miniature oven with twin

heating systems

• Heating-control and electronic modules

• A back-pressure vessel and

control system

• A computer and computer interface

for data recording and monitoring

• Differential pressure transducer

The HTHP tube-blocking equipment

can be operated at system temperatures in

the range of 392° F (200° C) and pressure

conditions in excess of 3,000 psi (207 bar).

The unit’s HPLC pumps allow a maximum

flow rate of 50 mL/min. All data is col-

lected by the computer, allowing easy

organization and presen tation of the

information generated. We also operate

three low-pressure rigs in which pressure

can be more accurately controlled for

carbonate-scaling regimes.

HTHP core-flood apparatusOur scale laboratory is equipped with HTHP

core-flood equipment used to monitor scale-

inhibitor adsorption and release character -

istics under reservoir conditions. It can also

examine potentially harmful mechanisms

such as fines migra tion, clay swelling and

chemical damage associated with perform-

ing well-intervention treatments.

Our core-flood test equipment can be

operated in temperatures up to 392° F

(200° C). The test fluids are contacted

directly with a temper ature sensor, allow-

ing accurate temperature measurements.

The maximum confining pressure is

2,500 psi (172 bar) and the maximum

operating pressure is 1,000 psi (69 bar),

with normal levels being 2,000 and 250 psi

(138 and 17 bar), respectively. Standard

Hastelloy^ core holders are suitable for

1- and 1.5-in. (2.54- and 3.81-cm) diame-

ter core plugs with a

maximum length of

3 to 6 in. (7.62 to

15.24 cm). A maxi -

mum system flow

rate of 500 mL/hr

is obtainable. The

core-flood rig can

also operate in

reverse flow.

Injection water Formation water

Water bath attest temperature

Water bath attest temperature

Stage 2Brine

mixingStage 3incubation at testtemperature

Stage 1Inhibitor

closing

Objective: Compare soluble cations (Ba, Sr, Ca)before and after incubation.

Dispenser

Scale inhibitorsolution

Prewarmedglass bottlesnominal 100 mL

After incubationfiltration andstabilization by EDTA solution

Solution ASeawater

Solution BFormation water

Scale inhibitorsolution

Pumps

Pressure

Time

Effluent

Narrow — 1 mmcapillary coil

Water bath or incubator

Concentration inhibitor ppm Inhibitor A and Inhibitor B100,000

10,000

1,000

100

105 25 45 65 85 115 150

Inh A

Inh B

Pore Volumes ElutedNorth Sea Field, Core Compatibility Trials

Our ongoing commitment to scale preventionThe scientists at M-I SWACO are con-tinually developing optimized scaleinhibitors for demanding applica-tions. We are involved in joint R&Dand technical service projects withcustomers and raw material suppliersto help protect your production fromreservoir to surface.

Biopolymers for “green”downhole scale inhibitionM-I SWACO remains at the forefrontof biopolymer development for down-hole scale inhibition. Biopolymers areconsidered the most environmentallyfriendly chemistry used for topside/subsea scale control. Biopolymerchemistry meets the requirementof no harmful discharge to the sea,because the molecules are completelymineralized after discharge.

While biopolymers have been usedfor scale squeeze, they require opti-mization for temperature stabilityand adsorption/desorption proper-ties in the reservoir. Technologydevelopment has yielded several molecules that are temperature- stable above 248° F (120° C) and thatshow outstanding efficiency for scaleinhibition: even better than tradi-tional phosphonate chemistry. Ourresearchers are also evaluatingthe in-reservoir adsorption propertiesof this promising technology.

Environmentally friendly scale-squeeze inhibitorsTraditional phosphonates havebeen used extensively for scalesqueeze, but their geometricallylocked backbone and sterically hindered functional groups preventbacteria from breaking them downin seawater. Phosphonates are pre-ferred for scale-squeeze applica tionsbecause of low Minimum InhibitoryConcentration (MIC), long treatment lifetime, and low-level detection monitoring.

Ongoing research has identifiedsome phosphonates that show sig -nificant biological degradation in seawater. They are being evaluatedfor efficiency, temperature stability,adsorption/desorption properties,detection in produced water, andcompatibility. These biopolymers(polyaspartates) have been usedfor topside scale control for sixyears in the North Sea. In addi -tion to being regarded as the

most environmentally acceptable scaleinhibitors on the market, biopolymercapability now extends beyond 194° F(90° C). Five different polyaspartatemolecules with temperature stabilityup to 248° F (120° C) for at least 24 hrshave been identified. As a result ofthis work, new polyaspartates wereselected for subsea continuous injection at client installations.

Halite inhibitorsTest results using field cores in NorthAfrica showed no formation damagewith applications of newly developedhalite inhibitors. Testing is also underway for squeeze applications.

Need more information?To learn more about how our Scale-Management Technology can help you get the most out of your investment, contact your localM-I SWACO repre sentative for casehistories as well as an assessmentof what we can do for you.

P.O. Box 42842Houston, Texas 77242-2842

www.miswaco.comE-mail: mipc@miswaco.com

Technology Centers:

HOUSTON, TEXASTel: 281·561·1300 · Fax: 281·561·1441

STAVANGER, NORWAYTel: 47·51·577300 · Fax: 47·51·576503

Technical Service Centers:

NISKU, ALBERTA, CANADATel: 780·955·3388 · Fax: 780·955·2064

ABERDEEN, SCOTLANDTel: 44·1224·285500 · Fax: 44·1224·890904

BERGEN, NORWAYTel: 47·55·173850 · Fax: 47·55·173851

DUBAI, U.A.E.Tel: 971·4·8830644 · Fax: 971·4·8837197

PERTH, AUSTRALIATel: 61·8·94402900 · Fax: 61·8·93251897

©2004 M-I L.L.C. All rights reserved. *Mark of M-I L.L.C.

^MultiScale is a mark of Petrotech.PBR.1901.0812.R2 (E) 2.5M Litho in U.S.A.

This information is supplied solely for informational purposes and M-I SWACO makes noguarantees or warranties, either expressed or implied, with respect to the accuracy and useof this data. All product warranties and guarantees shall be governed by the Standard Termsof Sale. Nothing in this document is legal advice or is a substitute for competent legal advice.