SPE

SPE 23075

Emulsion Cement

i.,

P, Skalle and J, Sveen, U, of TrondhoimSPE Members

Copyright 1951, SOCkrlyof Petroleum Engine6r5, Inc.

rhis paper waa prepmd for prasanta!ion at the Offshore Europe Conference held in Abordean, 3-6 SepleN ber 1991,

rhis peper waa 8elocted for presentellon by an SPE program Commiltea following review of information contained in an irbslracl submitted by Iho author(s), Contents of the paper,aepreeemed, have nol fx!ert reviewed by the Society of Pelroleum Engineers and are eubjecl 10correction by tho author(s). The malarial, as preeented, does not necessarily reflectmy position of the Society of Petroleum Engineere, its Ofticors, or members. Papere presented at SPE meetings are 6ubjecl to publication raviaw by Editorial Committees of the Society)f Petroleum Enginwrs. Permissionto copy la rostrictad to an abstract of nol moro than 300 words. I[lwtratlone may not be copied, The abstract should conlakr conspicuous acknowledgment>f where and by whom the parror Is prwanled. Write Librarian, SPE, P.O. Box 833838, Richardson, TX 7S083-3836 U.S.A. Telex, 7309s9 SPEDAL,

Gas leakage through cement in the annularspace around a cemented casing is still aserious problem although new additives andimproved techniques have reduced the

problem, A new approach is the constructionof an emulsion cement, consisting of adouble emulsion; water-irr-oil-in-cement ,Waterdroplets containing a controlled numberof species are emulsified into mineral oil,This W/O emulsion is then emulsified intothe cement slurry in small amounts (3-15 vol%) , The effect of the emulsion an thecement slurry has been recorded throughstandard API tests. In addition the bor,dbetween cement and steel. surfaces and thetightness a~ainst gas migration have beenchcckcd, Compared to ~ther cement slu~ries,the emulsion cement shows promising resultswith respect LO becoming a friction reducerand an anti gas mig~ation additive. Furthertcscs are necessary to dctertninc theapplicability of emulsion ccnmnt. CementSlll~E~.CS behave different at hightcmpcraturcs, and test pz’ocedurcs and Lustequipment Inust bc itnprovcd in ord~r LO

comply with down hole conditions.

—.—

stopped at the well head, This type of gasmigration can be dangerous and give blowoutsand accidents. Even if the leakage isdiscovered before this Ilappens, expettsiverc+pairsmay become necessary.

‘Thecauses of gas migration are caused by

- free water- water loss- poor bonding to the surroundings- 1.O.CSof hydrostatic pressure

Free water that i,s emitted during thehardening and settling process can developwater pockets in the hardened body. Thesewater pockets can evolve into communicationchannels for gas when the water issuppressed,

Chemical processes, temperature variations,and filtrate loss can cause crccping of thecementing s, ‘cry during the solidifying andhardening period, Mechanical stress duringCIIQ following drilling and perforatingoperations may crcatc cracks irr the cement,

Di.f’ficulties in obtaining good contactL)ctween the cementing slurry and theenvironment, and in suppressing the drillingmud may Cause channels and gao migration,l~ufcrlcthu solidifying process starts, thr2Cement behaves like a liquid transtcrringl)ydrostatic [Jrctiullrudcpcr;dinq on cicnuityand deptl). Early in the procesfi, Lhu cemcrrtstvps behaving like a liquid, but rathur au

d plastic slurry with weak. bonds and withfKc!cwater in the voids, A volume reductionof the free water in the void structure willLhcn cause a prcssurw reduction, Klven withadditional Substances in the cementingslurry, which reduces Lho filtrate, water

.

307

2 EMULSION CEMENT SPE 23075

loss cannot be totally prevented, When thepressure in the cementing slurry sinks underthe formation pressure of the gas, gas willeasily penetrate into the cementing slurry.Gas will migrate” upwards in r.he solidifyingslurry and leave cha.mels th;ough which moregas can stream. Some of the processesduring cement slurry thickening and settingmay be summarized as suggested in f.ig.1, Inthis figure tne following processes areshowr, in a c vnmor,time scale1~2:

- heat generation- internal matrix contraction total

chemical contraction- API thickening time- hydrostatic pressure reduction in a

cement slurry

mRLLE&JIL!!lLwuuQm

Water channels are easily created becauserelatively large amounts of water must beadded to the cement slurry in order toobtain sufficient pumping time, Methods forbinding the free water which is beinggenerated during the hydration process areknown, such as addition of bentonitepozzolan, expanding psrlite etc. Theseadditives have little or no effect on thepressure reduction, but give a certainnegativ? effect on other properties of thecementing slurry, such as the ~bility to bepumped, and the strenth,

Physical techniques can help con~rol gasmigration to some extent, External casingpackers, epoxy seal plugs, and annular backpressure are examples of physicaltechniques, but none of them can solve theproblem of gas flow through the cementmatrix.

Compressive cements an be obtained throughin-situ generation of hydrogen gas from Al-powder, Due to low compressibility at highpressure a lot of gas is necessary tomaintain pore pressure. Fire hazard andcoalescing tendency have minimized theapplication of nitrogen,

With expansive cements (small amounts of Al-powder for instance) successful fieldresults have been reported~, especially havethe bond between ;he cement sheet and theenvironment been improved, Although thesec~m~nts undergo a bulk dimensionalexpansion, they still cxibit a net chemicalcontraction., and expcricncc the samehydrostatic and pore pressure decrease asnoncxpdnsive ccmcnts7, Several methods havebeen developed to reduce the mat~i.xpermeability of the cornent system during thecritical liquid-to-solid transition period,Ilntih Latex, solid polymer particles(including surfacLants and protectivecolloids) and more recently micro silicahave shown positive cftect on cementpermeability, }iowever, it does not producegas tight cement at higher temperatures

(>1500C). Test results are inconclusive andirreproducable4.

ON

Emulsion cement is a patent protected methodto create a cement slurry which may hardenin two or more time steps5. The mainintention of emulsion cement !.( to make acementing slurry that eliminates the risk ofleakage after hardening, It is especiallyimportant to eliminate the problem of‘ertic..lcommunication of fluids along theexternal surface of lining pipes in oilwel~s ,

The above o.jects, IS well as other objectsto be made apparent, are achieved by the useof emulsion cement. The method of preparingsuch a slurry comprises the steps of

a,

b,

c.

Fig,2

forming an inner liquid phase. Thispaper deals with water being the“inner” liquiddispersing the inner liquid into aliquid capable of forming anencapsulating membrane . Thisdispersion forms the first emulsion.dispersing the first emulsion in acement slurry to form a dispersion ofmembrane encapsulated fluid in ahardenifig cement slurry.

shows schematically an emulsificationof liquid irto oil and the structure of thefirst emulsion. Fig.3 shows schematicallythe production of an “emulsion cemeni” ba.$?don the previously prod’iced emulsion whic!l isdespersed in cement (or water) . It tilso

shows the structure of the final cementingslurry, No water channels will be formed inthe cementing slurry because the free waterwill be taken up in the first emulsion byosmosis . The first emulsion will behavelike a viscous fluid, assuming it will notreact with the cement, and therefore fill upcracs and cavities arising h the cerr.entslurry during hardening/expansion/con-traction, The first emulsion will behave asa plastic filter loss reduction agent. Theemulsified particles have a broad particlesize distribution, from (’.5mm and upwards.The invention will also contribute to assureadhesion between the cementing slurry and anoil based filter body because parts of thecementing slurry are soluble in oil and canbe mixed with or diffuse into the filterbody . The invention will also preventdctcriorat.i.onand formation of cracs causedby external mechanical reasons, such asdrilling and pc!rforation, because theccmcnt!:,3 slurry become’s more elastic thanprior art mixtures, The invention can alsoadvantageously be tr~il~~~d in Connection’with common API-c!ements as a retarder,

Examples of materials suitable for creationof a membrane are mineral oils, vegetableand animal oils, marine oils and variousIlatural and synthetic polymers, such as

-.— .— . . ...—

398

rSPE 230?5 P, SKALLE, J, SVEEN 3

.—

silicones, latexes and natural rubbers, Inthis work mineral oil was applied,

Other positive side effects may be:

--lubricants; better rheology- Surfactants; may entrain invading gasand create stable foam which presentsignificant resistance to flow due tosurface tension.

One objective Las been to produce a stablewater-in-oil-in-water emulsion, the outerwater phase being represented by the cement.?uch an emulsion is shown in fig,3. Toreach this objective, it was necessary toperform the tests in three stages; firstfind a stable water-in-oi-emulsion (W/0),secondly determine a stable oil-in-water-(0/W)emulsi.onand thirdly test the stabilityof the double emulsion W/O/W. The testmatrix is shown in table 1, where all thecomponents are defined. To prod~ce W/O-emulsion, oil and the W/O-emulsifier weremixed thoroughly for 1 min. in a colloidalmill, The minimum necessary amount ofemulsifiers (assuming a molecule weight of1500) was estimated to be 1,3 vol $ of theemulsified phase, The estimation were basedon these assumptions;

1, One molecule of the emulsifier willcover an area of (50-100) , 10-20m.

2. The water droplets have an averagediameter of 1.15 mm (found by dropletsize distribution analysis6) ,

Some of the emulsifier will be distributedin the continous phase and thus beinefficient. More than 1.3 vol 8 willtherefore be needed. Stability tests(electric stability tests and gravitationalsettlement tests) pointed out that it wasnecessary to add 4 or more vol % emulsifierof the emulsified phase in order to reach astable W/O-emulsion, This is shown infig.4, Fox the tests reported here 4 vol %emulsifier was applied for bcth types ofemulsion, If less emulsifier is added itwill be insufficient to cover all thedroplets, They will stabilize at largerdroplet sizes, the coalescence tendency will!.ncrease and the stability of the emulsionwill decrease,

The selection of emulsifiers was based ongravitational settling tests and study ofthe emulsion through a microscope overextendded periods of time, WO1, WOS and W02produced the smallest and most stabledroplets. As an example of the microscopestudy a WO-emulsion is shown in fig,5. Forall further investigations the twoemulsifiers WOI and 0W2 were selected,

In tests ?2 through 16 in table 1 the effectof higher viscosity of the membrane phasewas tested, Higher viscosity was achieveoeither by applying medisine paraffine(viscosity of 19f) cP) instead Of ~.l~neral

base oil (viscosity of 6 cP), oi adding

viscosifysr to the mieral oil. Thisre-tilted in extreme high s;ability buth alsolarger water droplets. High viscosity andemulsion stability have positive effect onwater loss but the diffusion rate of wat.?rthrough the oil membrane will be reduced.

In tests 17 through 21 do”~ble emulsions wereproduced, and one example is shown in fig,6.By increasing the W/O ratio of the inneremulsion the apperent viscosity of the inneremulsion WL1l increase. For later tests aW/O ratio of 2:3 (40 vol % water) wasselected.

I ‘“’e~ ‘he‘f’”” “f ‘a’t concent’~.,

Initial tests of the osmosis effect wereperformed with kalium nitrate (KN03) in theinner water phase. KN03 was applied inorder to avoid any reaction between salt andcement . In bottom part of table 1 thedifferent tests are indicated, In fig,7 apicture is shown immediately after mixingthe emulsion, containing 5 vol % of salt,and another picture one hour leter, Adistinct volume increase of the water phaseis seen,

The diffusion rate of water, m, is

proportional to the difference in speciesconcentration, AC, pr. unit length, AL, andthe temperature, T. AC/AL is the drivingforce behind osmosis. The diffusion rate isproportional to the reciprocal of fluidviscosity and particle diametert d (heze

diameter of water molecules), i.e. :

~l=T.AC/ALMod

If the number of ionS or Spt?Ci@S (mOleCUleS)per volume of water is higher in the ~nnerwater phase than in the surrounding cementpore water, water will diffuse into theinner water phase by osmotis.

The cement pore water (interstitial water)is saturated with CaOH, which results in ap~iof 12,6, In addition NaOR will dissolveand give a pH of about 13. At O°C Ca(OH)z

will dissolve 1.85 g/1 and 0.77 g/1 at 100°C(lower volubility at higher temperature).1,85 g Ca(OH)2 equals to 0,025 mol Ca(OH)2which dissolves into three species (Cat+ +OH- + OH”) whi~., leaves 0,0”)5 mol insolution,

At {IQC KN03 dissolves 133 g/1 and 24~0 g/1at IOOQC, 133 g KkJ03 equals to 1,315 molKN03 which dissolves into two species (K’ +

N53-]which leaves 2.63 mol in solution, The

1 .-

*

4 EMULSION CEMENT SPE 23075

species concentration is thus 35 timeshigher in the inner water phase compared tointerstitial water. Other spezies in theinterstitial water phase will reduce thisdifference, but not by far neutralize theosmotic force,

Micro silica consists mainly of siliconpowder (Sioz) . The particles, rangingbetween 0.1-0,2 mm, are pa?ked between thecement par:.icles and th~..eby reducing theeffective ilow area. The particles willalso buiid a physical structure within the‘interstitial water, causing theviscosity/:rield point of the water toincrease, Si02 reacts with Ca(OH)2 to formC-S-H (princ~pal binder 02 hardened cement),causing higher final strength and more,smaller pores. Micro silica is commonlybei~.g applied as anti-gas-migrationadditive,

When water is being consumed duri’lg thehydration process, che latex concentrationincreases. Latex particles will growtogether and form a continous, impermeablefilm, binding the partly hydrated cementparticles together. Latex is also commonlyapplied as an anti-gas-migration additive.Most latexes, however, will loose theirelastic ability ahd become brittle at highertemperatures (> 160°C) .

A new latex is now patent pending by SINTEF*

/FCB** 7. It is an acrylat latex, based ona terpolymer. The three polymer componentsare: 1) n-butylacrylat, 2) methymetacrylatand 3) a secret component which causes thepolymer to react chemically with the cement.At high temperature the :!atex soften andforms a film, like an ord.nary latex, Thetemperature at which the latex softens iscontrollable. This new latex has been~.ncluded in the test matrix,

lksfJnaLxix

Based on introductory tests of emuls:.m.s andosmosis effects a test matrix was determinedas shown in Table 2. The basic slurrycomposition consisted simply of water, G-cement and one additive. Bentonite andStarch were applied as a free water reducerand water loss ~educer respectively, Thesebasic slurries were compared with oneestablished additive, Mice-silica, and twonew additives, New Latex and Emulsion. Itwas especially the ability to reduce gasmigraticn and to increase bonding strenght

● !boundatlon for Scionti tic and industrial Rast?arch,TtondhuIm,

Norway

“ Cwncnt and Concreto Rosoarch tnstitutc, Tromlhc. dorway

to solid surfaces that was interesting tocompare,

The cemenc sll’rries were tested by fourdifferent sta,,dard API test methods inaddition to recording the density by meansof the API mud balance. The four test were :

- Rheology in a Farm rotational viscosimeter- Free water in 200 ml Sraduated glass

cylinders- Filter loss in low pressure filter cell- Con: istency in atmospheric consistometer

The results are shown in Table 4, A1lresults are the average of two tests, Incases where two identical tests differed bymore than 10% the tests were repeated.

Plastic viscosity (PV) and yield point (YP)is calculated on basis on the 2 upper shearstress readings , Filter loss is backcalculated for all tests to the water lossat 30 minutes.

Thermal, hydraulic and mechanical downholestresses are generally not taken intoaccount today, and should ‘-.heref~re beconsidered extra carefully, S=ch stress maycause micro annuluses and gas migration.The best manner in which negative effects of.downhole stresses are dealt with is toobtain cements with high bonding ability,

Thermal stresses are caused by thermalexpansion/contraction of the ce:nent/casing.Although the coefficient of linear thermalexpansion for cement and steel arecomparable (12.6.10-6/OC), they areheated/coled at different rate since theheatJcold is applied radially (from theoutside or the inside) ,

Pressure reduction inside the casing maylikewise cause gas migrations, In one case10where a lighter fluid replaced a heavierone, the 9 5/8” casing had its diameterreduced by 0,008 inches (203 Urn), and gasmigration was observed,

Mechanical stresses generated by drillingoperations several days after cementing aretransmitted through the casing, Such stresscan not be overlooked,To simulate bonding effects, the cementslurry was placed in hydraulic steel pipeson a plain surface with a steel cylinder ontop of it, as shown in fig,8. Hydraulicsteel pipes were used to obtain a highquality surface. The purpose of the steelcylinder was to obtain a plain surface forthe anvil of the axial strength tester. Anadditional purpose was to take away theinfluence of initial shrinkage, aasuming the

-— ..-.—.

400

SPE 23075 P. SKALLE. J. SVEEN 5

weight of the steel cylinder would overcome The addition of mo~-e than 1 weight %wall stresses during initial hydration. The ben;onite alone caused the viscosity tobonding forces would in this way be less increase beyond pumpabil.ity, On the otherinfluenced by shrinkage effects which hani, bentonite addition result?d inotherwise may mask searchecibonding effects. reduction of free water but the filter lossThe tes~s were performbd in three different was high. Bentonite reduced the bo~dingways: strength, and in this respect it acted as a

contaminator,Firstly the bonding strength was testedafter letting the cement harden for three Starch alone had no positive (or negative)days in the pipe under standard room effects on the cement. slurry, besides ofconditions. producing brittle cement and high shear bond

strength.Secondly the cement was also hardenej forthree days at standard room conditions, But The addition OL approximately 7 vol. %six hours before the bond test the steel Latex reduced the amount of tree water andpipe was placed in a 100°C hot chamber for a the filter ioss to a negligible level.period of one hour, and cooled with running However, the bonding strensth was reducedwater to ambient temperature. This procedure significantly, The Latex also developedcaused the cement and pipe to expand and severe f’oaming, which resulted incontract at different rate, and thereby difficulties in recording the specificdamaged the bonds between pipe and cement. slurry weight.An

An anti foam is necessary.

“elastic” cement would show higherresistance towards such reatment, Microsilica was tested only for one

concentration, The addition of 10 vol. %Thirdly the steel pipe was wetted with microsilica led to a very high viscosity butmedisinic paraffine before it was filled the 130nd strength was acceptable, Thewith cement slurry. Otherwise the tes~ wa~ slurry behaved as a very stable mixture atperformed identical to the test firstly static conditions; no free waterdescribed. The purpose of oil wetting the

wasobserved,

steel pipe was to simulate a well drilledwith oil based mud. Shear bond strength is The addition of emulsion to the cementrelated to nettability of the surfaces (and slurry had positive effects on its rheology,to the degree of hydration of the cement)8. Simultaneously the bonding stren3th was kept

at an acceptable level. Even the additionof 15 vol. % emulsion improved the rheology

.C@S~$@Ll&Sli without much reduction of the bond strength.The free water and filter loss values, on

A cement slurry’s resistance against gas the other hand, were un~cceptable high for

migration was tested in an atmospheric gas the emulsicn cement. In order to achieve a

rig as shown in fig.9. The following test gas tight (:ement it is necessary to reduce

procedure was applied: the free water and filter loss values.

1. Fill the 2 m long pipe with cement A new series of tests were run and the

slurry results are shown in Table 5, In these2. Record the slurry pressure at the tests 7 vol. % emulsion was added to all the

bottom of the pipe (approximately 0.34 cement slurries, plus 0.5 weight % bentonitebar, co free water and filter loss values,

3. Open for the gas and set the gas Inside some of the emulsions, salt was added

pressure to 1,5 times the water to the water phase, As seen from Table 5pressure, which is approximately 0.30 the rheology, free water and bondingbar strength were acceptable, wl~~le the high

4. Wait for the slurry pressure ‘o fluid loss is still left to be dealt with.

decrease below the gas pressure andrecord gas flow rate Only two ~amples were selected for special

bonding tesrs and gas migration tests. TheIn gas migration tests temperature and basic slurry containing w/c = 0,65 and 0.?5

pressure are important parameters. It i.S weight k bentonite was bond strength testedrelatively easy to obtain a gas tight cement in accordance with previoual.y explained testslurry at low temperatures, but not so at procedure, It was expected that the bondhigh. In our atmospheric gas migration rig strength would decrease when lining the pipewhere pressure- and temperature control are with oil and when heating/cooling the pipe.

missing, only relative or qualitative tests However, in both testt{ the bond strength

may be run. increased, Concerning the heating/coolingprocedure, the cooling lasted for only 10min. immediately prior to the bond strengthtest , This procedure caused only tile steel

pipe to cc~ntract and p.rabably not theIn Table ? the results of the primary tests complete ceme~+. body. T;”vegrip on the

are shown. cement was therefore increased, Theprocedure must be changed accordingly, The

—...-

401

6 EiK!T,SIONCEMENT SPE 23075

inc~e,?sed bond strencjth in oil lined pipesremained unexplained as this paper washanded in.

Three gas migration tests werr. run, a basiccomposition was run twice, i,nd the slurrycontaining 10% emulsion cnc~., The slurrycompositions and their properties are shownin Table 6. The gas migration results areshown In figs, 10, 11 and 12 respectively,At the bottom of the 2 m high test pipe theinitial, hydrostatic pressure of the cementslurry was estimated to 1730 x 9,81 x 2 =0.339.105 Pa = 0.34 bar, as ZISO recorded,The slurry water pressure in 2 m depth wouldke 0.20 bar. The gas pressure at the bottominlet was set at 1.5 the water pressure,i.e. 0.30 bar,

During the two tests with the basic slurry(figs, 10 and 11) the pressure dropped from0.34 bar to 0.285 in 300 min. for bothtests, At 180 min. the slurry pressuredropped below the gas pressure but no gasflow was recorded for any of the two tests,The gas pressure was increased in testnumber 1 and some gas int.ered the slurry.However, the hydrostatic pressure alsoincreased and the gas flow stopped after afew minutes . :~ince no gas flow wasestablished in any of these tests, thehydrostatic pressure drop was taken as anindication of gas flow resistance. As shownin fig.12, ..ne pressure in the emulsioncement dropped ?ess than in figs. 10 and 11and it never surpassed the gas pressure,

The basic cement slurry was run in anatmospheric cofisistometez, and the resultsare shown in fig.13. It was observed thatthe consistency measurements indicated alower thickening time thar, a still standingslurry, By observi,n$ the temperatureincrease in figs, 10, 11 and 12, +hehydration process started to acellezdte at.around 300 mi.n, in all cases. The slowhydration ir a still standing slurry may beexplained by the addition of mixiny energyapplied by the consistometer, liighermixingenergy causes better contact between waterand the individual cement grains (betterdispersion) and thereby faster hydration,

One reason why no gas migration occured inour test facilities may be: At lowtemperatures (21°C) the hydrat],on process isslow , The elastic-plastic nature of thecti,’ent slurry have sufficient time tocompensate for the pressure reduction causedby cement shrinkage. At high temperaturesdown hole the process is much fa:]terand theshrinkage effect may not be compensated for,

Based on the findings through theinvestigations reported in tiiis paper, thefollowing conclusions can be drawn,

—

1, A double emulsion is produced througha simple procedure? consisting ofmixing fluid ~~omponents and em!~lsi-fiel , in a cox]:ect sequence,

2, Emulsion stability is achived byselecting the proper emulsifier,adding it in a correct amount andmixing it sufficiently.

3, By adding salt to the inner wa~erphase, an osmotic force will becreateu causing water to diffuse fromthe interstitial water in the cements~ Irry into the wa~.er droplets insidethe oil dro~ ~ts. The osmotic force iscausing a rather rapid diffusion ofwater molecules through an oilmembrane, and the diffusion rate isdependent on the difference j-consentration of species in the t’.water phases,

4, Several additives were tested bystandard API test equiprnerit. A1.\ theadditives had some positi~~e and somenegative sides, Bentonite reduced thefree water content to an acceptablelevel (0.25 ml) simultaneously as therheology becan.s unacceptable. Starchalone had no influence on slurryproperties. The new latex productlowered free water, fluid loss andbond strength and developed foam.Microsilica behaved like bentonite;the addition of 10 \’ol, % ofmicrosilica caused a slurry behaviourwhich was almost an identic~l to Lheaddition of 1 weight % of bentonite,The emulsion showed promising resultswith respect to becoming a frictionreducer. Bond strength is acceptablebut fluid loss is tco high.

5. Based on a few qualitative gasmigration tests in an atmospheric gasrig, the emulsion cement showed signsto become an anti gas migrationadditive. However, tests must b?performed in an HTHP gas rig Loforeany conclusions can be drawn.

6, The thickening time of a cement slurrywill decrease when stirred or pumped,due to improved dispersion of cementgrains and thereby higher hydrationrate.

7. ‘rhe introductory tests reported hereshow some promising signs. Forfurther tests both procedures andbasic slurry compositions mus beimproved,

‘l’hisstudy constitute the initial phase of abroader iikuciy of gas mj.grati.on and has ~cen

made possible through the contributions fromThe Royal Norwegian Council for Scientificand Industrial Research (NTNJ?).

SPE 23075 P, SKALLE, J. SVEEN 7

1,

2,

3,

4,

5.

Parcevaux, P.A, : “Gas migration andgasblock technology”, Drilling & PumpingJ. (Aug. 1987)

Levine, D.C., Thomas, E,W,, Bezner, ..P.and Talle, G,C.: “Annular gas flow aftercementin~: A look at practicalsolutions”, SPE Paper 8 255 (19?9)

Nelson, E.B,: rlwell cementing. DCveloP-ner,ts in petroleum Science, 28”,Elsevier, %mst,~rdam (1990) Chapter 7 0Gas migrat; :n

Kalvenes, @,, Berge, L, og Tydal, T.:l~HTHp-gassmigraS jon”l Norsk HydroResearch Department., Bergen, Internalreport R-046338 (Feb. 1991)

Ghseidnes, K. and Johnsen, H,K, : ‘!Slurryfor cementing, especially cementing oflining pipes in drill holes, and methodfor production of such a slurry”,U.S,Patent number 4 650 .520 (March 1987)

6,

7,

8.

9,

10,

Hilde, T.: “Determination of type andamount of surfactant in oil based mudt],Diploma Thesis at Division of PetroleumTechnology, Univ. of Trondheim (March1990)

Justnes, H. and Bennington, S,P,:“Designing iatex for cements andnoncrete”, Nordic Concrete Research,\“ol. 7 (1988) 188-206

Becher, H and Petersc?, G, : “Bond ofcement compositions for cementingwells’!, Proceedings; Sixth WorldPetroleum Congress, Frankfurt, Germany(1963)

Parcevaux, P,>..and Sault, L?,H,: “Cementshrinkage and elasticity: A new approachfor a good zonal isolation”, SPE paper13 176 (1984)

Matthews, S,M, and Copeland, J,C, :“Control of annualar gas flow in deepAnadarko 13?.sin”,SPE paper 149&fi (i986)

TABLE 1-TEST MATRIX FOR TESTING EMULS1ON STABILITY AND THE EFFECTOFSALTINTHEINNER PHAS&

The abbreviahons are:NO =NorakOljeNo,4/5 OWl=Genapol UD088(HL13= 14,0)MP = Medltsin paraffin 0W2=C?enapcl UD 050 (11.0)v =Ti?m Water OW3 = Berol OX 25.3 (8.1)z =KN03 (salt) WOlrEmuht9gen OG (4.0)PPB=g/350rnl W02=Span85 (1,8)

W03=Bero1055 (6.5)

Testm,. Mm 94

1 vL I I 1 1 1 I !

3 I. !, !, “

1 2 I 1. !, ,, 1 1 . . I vm A I. 1 1 1 , , .- , ,

7 I NO 2 I 1 v 10 I 1 Ov 1 4 I I. m n.m A Io I ! 1 m ,1

I~- “.. T

r) 1 !, . I I 2 I I-lo I “ I ,, ,, .111”” I . . I I 0V3 4 I I12 I v 1 1 I Nil 1 1 MP 50 I V02 4 I 1

b

13 “ “ htP 2 . .

-17 “ I I“.

1 1 v01 “ I I..,” “ .“ . ..- .

.“ , ,, .

10 I f I mr I 8 1 1

19 1 “ I I I Vol 1 1 WI*n 1 “ ,. 1 w,~ ,, ,, ., 4, “ (m ,, Ixl 1 I 1 1 I 1 1

4221

I v 1 I L 1 1 M P 2 I WC)34 1 v 5 I OW 4“23 I “ ,,

“— - ,, ,, ,, ,, ,, ,,5 I “ “

24 I “ 1 10 I I. ,! 1! 4, !! 41

TABLE 2-TESTMATRIX FOR EMULSION CEMENT AND OTHER CEMENTC!)MPOSITIONS

?arameter Unit VaratianWlc Welqht quollent 0,65Bwmnlle welghl ‘k of water 0,20 0,5 0.75 1!0Stare:* weightYeof water 0,25 0.5 1 1,5 2

Lalex VOI%’oof water phase 3,0 5 10 15 20Mlcrosllica vol.% of water phase 10Emulslon VOI %’. of water phase 3,0 5 7 10 15

— —. .. .—-403

TABLE 3-COMPOSITION OF EMULSION CFMENTS WITH DIFFERENTVOLUMES OF EMULSION AfJDED TO THE CEMENT

The specific emu1610n compoaltlon is:● W/C= 0,65 (weight quotient, cement slurry)

● W/O - M (volume quotient, emulelon)c W/Cl and O/W emulsifier= 4 VOI% of emulelfled liquid volume

Parameter Unit I Variation -W/O-emulsion Vol % ; 3 5 1 I 1(J 1 15\Vator ml 1500.0 (1 ,5kg)‘Jement ml 732.5 (2.307kg)

011 ml 40.2 67 93,8 133.9 200.9W/O.emulsifier ml 1.1 1.8

~’ +

:?,5 3.6 5.6-Water ml 26.8 44.6 -693 13s,9OW.emulsifier ml 2.’! 4.5 6,3 6.9 13.4

TABLE 4-RESULTS OF ALL PRIMARY TESTSSpacea marked with ? mean no data point waa recorded.

Additive Mntonlte :wrriqhtt) 3tatcn (Welqht *I LatexVol, or welqht t ofslurry water ,29 ,5 0,”75 ‘.0 .2! .s 1.0 2,0 3 5 10 15

-!

Welqht [SpOCifi C)

Pv (CP)

Ye (l b/loo ft2)

FrOQ water (roll

Fi:. cr 10ss (ml) 1 min.

‘130nd (plain)

1,73 1.73 1!73 1,”)2

19 14 13 13

9 27 58 63

8 1,25 1,4 0,23

30.0 22,3 38 14, s

35,0 23, s 11 10,0

1.?3 1,7’3 1.”)2 1.72

14,3 13,5 14,5 17.5

6.5 6.0 6.0 0,5

12,9 14,8 16,4 6,7

34.0 11,6 34.0 20. ?

45,8 41.4 43,8 23.0

1.4 1,5C !,15

25,5 18,5 i6 f14

-3 -4 -2 f)

2 0 0 0

59 34 4 3

17.0 12,1 10,7 3,1

1,”13

2145

65,5

0

19

),61’4” 2“uLuuu.1

=Weight

Pv

YP

FW

FL

Bond

1.6“1 1,64 1.65 1.56 1,50

13.5 13,0 11.5 14 14,5

4 4 0 -1!5 -3.5

12,1 15, ? 10.9 20,0 28,6

45 40 41 35 ?

TABLE 5-TEST REbiJLTS FOR CEMENT SLURRIES IN WHICH 10 VOt% OFEMULSION WAS ADDED

In the five Ieft.hand+lde teste, mineral oil wae armlled as oil Phase, while In thetwo right.hand.slda teats, medlahr paraffin waa. applied. The slurry water wae

mixed with 0,5 wel!iht% of bentonite (B) to reduce free water and avoid aettllngdurlng”hydration.

o.o13 o,5i3 0.50 0.50 0.50

16g/1 66 g/1 133 g/1

1,65 1.69 1.70 1.72 1,68

11,5 19 10,5 15.5 19

0 2 18 8,5 12

18.9 13,7 J.4.2 8,9 7.9

47 67 57 37 46

19.9 14.5 15,1 11.3 15.6

0.513 0.5B ~

133 gll

1,64 1.68

21 19

17.5 14

3,5 5.9

64 37

22.4 19.8

TABLE 6-RESULTS FROM SPECIAL BONDING TESTS AND GASRESISTANCE TEST

Additives : vol. % Of BrmtonLte 0.75%B 0.5 s B91urrv water, Emulsion o 10

Salt. nctckd to inner wiitnr ((3/ 1) o 66

WOight (spucific) 1,73 1,72

pv @ 13 15,5

YP !lb/loof’t2) 58 8,5

F’rw water (ml.) 1,4 0.9

FreG wa~cc loss (ml) 98 37.0

130nd (plain) l~,r) ln,3

130nd (heat) 22.4 ?

3ond (oil) 14,6 7

%sflow o 0

,API thlckt?nlng time

+-t-latrlxinternalcontraction

Interstltlal —.. —water

/=pressure +-Cement slurrytemperature

< “Cement pore pressure

oTotal chemical

12 s Ic 20 contraction

Time (fir)

Fig, l-Development ofdlfforent processes lnacement slurry asafunctlonoftlme,

Fig. 2-Production of W/O emulsion.

Inner phasc(wiitcr)1

Mornbranc phase(oil+W/O-eraulsifyer) _ \

Continou9 phaac(fluId+O/W-cmu!9ifycr) ‘7 \\

WYO-emu18ion

D

After mixing

WaCu or cman’c +o/w-aLuuhify(mr

Fig, 3-Production of double emulslon,

& \ \

“.

405

c)

100

wl+-* a“ 4 * e 10

ArnounlO(UIrfaclant (wclghl~ of llw waler phasd

9’ 2 4 G u 10

AH14UIIIOfSurhclanl(Wclgllk!bd IIICWt!lCrpha~)

Fig, 5-Microscope picture of a W/O cmulslon. 4 VOI% ofW/O, omulalfler, Only 12 seconds mixing time wasapplled, which Is Insufflclent; It results In manylarge droplats, Ths arrow Is 10 pm long.

Fig, 6-Mlcroscopa plcturo of a double emulslon, Inner andouter phase IR water, membrane phaso Is mlnoral011. W/O 1 and O/Wa omuldflera are applled,

406

., SEE 23075

Fln 7-ti:nrormape picture of double emulsion after 0 mhl,l!t (?~tt) ml ho m!nutes (rlffht), Inner waterphase containa 5 vol% nf salt (KN03). The alze ~: fha I,fi,’yt 011 droplet hall Increased(approximately 3%), and the water droplets Inside W@ OII@$ r~ii dfoplat havo als,, IncreasedIn volume,

Fig. 8-Equipment for testing of bonding strength,

oT —-

0P—

FIu, 9-Atmoopharlc uaa rig,

40?

SEE 23075°

0,3

0,2

PQImPcomorrtT

0,1-i-—1”~ 40 ;00 200 300 400 Lioo

Tlmo (mIn)

Fig. l-7-First gas migration tett, performed with brmlc slurry,

‘“L’”A‘●**.,

● e0,3 ● ***.**

● a...,.

0,2

P gnuP cernont

T

,J---J-J100 200 300 400 500

Tlm ● ;~!n;

Fig, 11-Second gas migration test, performed with basic cement elurry,At 180 mlmrtcm (3 hours) the slurry presrwm falls below thogas preetwre, but rm gae flow was racorded at the outlet ofthe 2.m high pipe,

● ☛☛☛☛☛☛●☛☛☛☛☛

●☛☛☛☛☛☛☛☛☛☛ , Pcamont0,3- Pgau

T

0,1 I 1 1 1 I

o 100 200 300 400 500

Wm. (mIn)

Flfj. 12-f3ria mlorutlon teot, porformod wllh omuldon cement, Thocomorrt slurry farermuro nevar dewmdn to the san presauro,

flo I 1

70 “ ●

●: Go. ●

~60 “ ●

t 40”a ●

: 30- ● ●m

c 20. ●O**

10”

0 ! 8 1 I -70 100 200 300 400

Time (mIn)

Fig, 13-Cr)nelrWroy of a baalc cement olurry oompooodau ehown In Table 6, An etmoapharloconslutometer waa appllod and wetor bothtemperature woo kept at 21 ‘C,

400