E-Library15464 Mud and Cement for Horizontal Wells

8/2/2019 E-Library15464 Mud and Cement for Horizontal Wells

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SPESPE 15464Mud a! 1 Cement for Horizontal Wellsby C. Zur JO and C, Georges, E/f Aquitaine, and M. Martin, h?st. Franqais du Petro/e

Copyright 1986, Society of Petroleum EngineersThis paper was prepared for presentation et the 61s! Annual Technical Conference and Exhibition of the Society of Petroleum Engineers held in NewOrleans, LA October 5-8, 1966.This paper was selected for presentat ion by an SPE Program Committee following review of information contained in an abstract submitted by theauthor(s). Contents of the paper, as presented, have not been reviewed by the Society of Petroleum Engineers and are subject to correct ion bytheauthor(s). The material, aapresented, does not necessarily reflect any position of the Society of Pelroleum Engineers, its officers, or members. Paperspreaenled at SPE mee!inga are eubject to publication review by Editorial Committees of the Socialy of Petroleum Errginaers. Permission to copy iarestricted to an abatract of not more than 300 words. Illua!rations may not be copied. The abalract should contain conspicuous acknowledgment ofwhere and by whom the paper iaprasanted, Write Publicafiona Manager, SPE, P.O. Box 833836, Richardson, TX 75083-3838. Telex, 730989 SPEDAL.

ASSTRACT Therefore,several full-scaletest benches (25 to300 m in length)were set up in order to studyHigh-angle and horizontal well bores raise many the following cement placement parame-questions concerning the characteristicsof mud ters : caaing-hole eccentricity, drilling fluidand cement. This paper is a summary of our know- rheological behaviour, hole geometry, spacerledge and work on these two subjects. design (rheology and density), flow rate, etc.Furthermore, slurries without free-water wereFor all researchcarried out, large or full-scale studied for varying downholeconditions.laboratorytest plantswere used. INTRODUCTIONCutting tranaport la not only a problensin hori-zontalconditionsbut hole angles of 25 to 65 can The successful dr?.llingand production of abe even more criticalwhen parameter cuch aa mud horizontal well degends largely on the fluidstheological properties and velocities are not used during the drillingand completionphases.optf .zed. If actual horizontal drilling techniquesappearDrillinga long horizontaldrain createaa dynamic to have been perfectednowadaya in more or lessaanulus pressure unbalance. This can lead to a favorableenvironmenta,it shouldneverthelessbel.ossand kick situation. Two teat benches were borne in mind that numerous difficulties maythus used to obtain a good understandingof the arise and that a well-designedmud will ofteninefficiencyof conventionalpluggingmethods and solve such problemsas :of the difficultiesof gas migration control insubhorizontalwell bores. High concentrationsof - poor borehole stabtlity,unconsolidatedaand,LCM, high theologicalpropertiesof fluidsand low awelling$ ruptures due to tectonic stress,flow rates increase the chances of solving the shale sloughing,etc.,first problem. Tne results of the second benchdemonstrate the difficulties of annulus gaa - hole cleaningdifficulties,incorrectapprecia-evacution for angles varying from 90 to 100 tion of actual hole diameter and thus of muddegreea,or from o~-er-gaugedections in horizon- velocity, difficult evacuation of cuttingstal holes, according to angle, and possible build-u: on

the undersideof the well bore, etc.,Cementing horizontal casing strings is still afairly new practice. However a good casing/forma- - annulus pressure instability in a constmtion cement bond is certainly the beat neana of pressurereservoir,etc.obtainingcorrect well productivity.A successfulhorizontalcement job shouldpreventthe formation Successful cementingin heavily inclinedor evenof mud, water and gas channelsand of a free water horizontalsectionsla often a necessaryprerequi-channelon the upper part of the drain hole. site for eased completion.

Referenc= and illustration at end of paper.


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2 MID AND CEMENTFOR HORIZONTALWELLS SPE 1546

To obtain this goal, cement slurry compositionand HOLE CLEANINGdisplacementwill have to meet numerous criteriacommon to all cementing procedures but will also Once al,lother parametershave been studied andanswer to much strictertheologicaland free water defined (mud weight, filtrate, salinity, solidsconditions. content, etc..), it is necessary to adapt therheology to provide a sufficientcarrying capa-The followingchaptersprovidea globalview of the city of the mud along the annulus varying inproblemswe encounteredand our attemptsat dealing inclinationand size.with these problems, taking advantage of standardpractices, of our know-how, of our research~ and As opposed to what happena in conventionalwellsfinally of our wide experience in horizontal (increasing thixotropy improves cutting trans-drilling carried Out on our own behalf and for port), in highly deviatedwells and even more soother companies. in horizontalwells, the drilled cuttingshave tocome up through variously inclinedsectionsfromCHOICEOF MDD TYPE 90 to 0 where the optimum parameters requiredfor hole cleaning may vary greatly Zrom oneA combinationof very high angle and poor quality section to the other.When drillinghorizontally,reservoir 1 might require more complex drilling cuttings transportationphenomenacan be classi-fluid specificationscompared to those used when fied in three different ranges of inclinationdrilling conventionaldirectionalwells, not only separatedby two criticalangle values Oa andbecause of the increase in angle, but above all o) .because poor quality reservoirsdo not tolerateanyfurtherdegradationand in order to avoid expensive Why two criticalangles ? (Fig. 1)and/or problematic stimulating treatments. Thusbefore talking about hole-cleaning techniques it When drilling a horizontal well from O to 90,should be pointed out that as we expect more from the in~luenceof the axial component (V ) of thehorizontal wells than from vertical wells, particle slipping (V ) decreases as %eviationadditionalprecautionshave to be taken to : increaaes. $n the con rary the radial component(VSR) of he particle slipping velocity (VS)

avoid damage to reservoircharacteristics, increaaestowardsthe low part of the well.avoid incompatibilitybetween reservoirformation 1. Sectionswhere the inclination rangesbetweenand fluid used, 0 andllm .ensure bore hole stability (in inconaolidated In this section the radial component of theformations), slipping velocity (V ) is null and increasesas O increases.tJasRia the critical angle

- provide lubricity to decrease torque and drag, here % is sufficientto make the particlesand hence, the possibilityof sticking of drill leave t e mud flow and lie on the low aide ofstringand casing. the annulua with a tendency to slide downagainst the currentdue to Vaa.When examining these specifications, it seemsevident that an oil-base mud will be the aafeat ?. Sectionswhere the inclination rangesbetweenchoice of drilling fluid. In fact, when oil-base @a ande~ .mud haa not been the fluid used for drillizgneighboring verticalwells, as for as we know this As 6 increases from 8 w to 0/! , V conti-mud type has never been chosenbecause of the high S$nues to grow thus increasing the ten ency ofangle of deviation. The main reason for this is the particles to lay on the low side of thethat when properly designed (choice of salt and hole, but in the meantimeV decreasesandconcentration) and when enhanced with specific Ofl is the critical anglea%here V ia notadditives (lubricants,asphalts,diesel or mineral sufficient to make the cuttings s~~de backoil), low solids brine water-basemud has auccess- against the current.ftillycompeted with oil-base mud. Their characte-ristics are easily and rapidly adjustableto hole 3. Sectionswhere the inclination rangesbetweenrequirements.In addition,leases can be prevented 6P and 90.and cured more eaaily (sizedcalcium carbonatecanbe often used eitheir as a weightingagent or as a Aa d increasesfrom (7/3to 90 the influencetemporarypluggtngagent).This ability iS @f prime of the axial component of the slippingvelo-importancewhen drilling through fractured forma- city decreasesand reacheaa value of O whentiona and alao to build up a firm and acid-soluble O equals90.cake againat unconsolidatedaand formations (i.e.Chateaurenard- 350 meters ( ..1150 ft) horizontal Discussionper Intervalof Inclinationthrough incosolidztedsand). Horizontaltest benches, theoreticalcalculation,and field experienceallow an estimationof the

criticalangles :25 to 35 for @a55 to 65 for 0~


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SPE 15464 Ch. ZURDO,Ch. GEORGES,M. MARTIN 3.

1. Sections whe~.~ the inclination is less than This table does not integratethe effect :(25/350) - particlesize distributionof cuttings*,Laminar flow is convenient in the event oftroublesomecoarse cuttings.The YP/PV ratio has - cuttingsconcentration**,to be increaaed.If required,the circulationofhigh viscosity pluga is suitable in this range - ahape of cuttings,of deviation. tendencyof the cuttingsto agglomerateor not,2. Sectionswhere the inclinationis greater thanOm and less thanO/~ (25/350to 55/650) - differenceof densitybetweenmud and cuttings(tulkdensity),These sections are critical not only becausecuttingsbuild a bed on the low side of the hole - ovalizationof bore hole,but because the bed may have a tendencyto slidedownward by the effect of gravity at least when - pipe rotation.the pumps are stopped.This might eaailylead toa stuck pipe situation,unless all the cuttings FLUID BALANCE IN HORIZONTALWELL BORESare circulatedout prior to tripping.The bestcompromise to clean up these critical aectiona Horizontalwell borea often have to cross reser-is to ensure a sufficientmud velocity (0,9 to voirs of varying permeability (e.g. fracture1 meter/second = 3,3 ft/s) associated with a production) but will remain in formations ofhigh YP/PV ratio (greater than 1 with yp approximatelyequal pressure.(lb/100ftz) and PV (cp)). If the minimumvelocity is not possible (rig pump capacity, Given ;R reservoirpressurebore instabilityor down hole motor limitation) mud pressureunder the bit

the YP/PV ratio and circulatingtime have to be JP2 annuluspressurein the horizontalincreased. part3. Sections where the inclinationis greater than We immediatelysee the difficultyin maintaining(55/650) a fluid balance in a long horizontalwell bore,above all when certain porosityand permeabilityOvalizationof the bore hole should be expected characteristicsof the reservoir will not with-and, in addition, the cuttings have a tendency atand a big difference between the reservoirto settleand concentrateon the low side of the preaaure and the equivalentcirculatingpressurehole around the drill pipes. In this range of (see Figure 2).angle, the bed of cuttings does not tend to

slide downwards even when circulation is PR constantstopped. When acceptable, turbulent flow iSdefinitelyrecommendedto prevent cuttings from -IfPB=Psettling andlor to erode them. If a bed still B - A!a < PR risk of kick at theexists, it thickness will be related to velo- beginningof hori-city. Tle time of circulationmust be increased zontalwell borewhen turbulentflow is not permitted.Note thatpipe rotation will help to unstaliblize such -IfP -APa = PRbeds of cuttings. P: > PR risk of circulationloss at bottom ofBefore leavin~ the question of hole cleaning, we horizontalwellwould like to point out that sophisticatedcalcu- borelationswill bz useless if not backed up by commonsense and empirical knowledge. The best way to It is thereforeimportantto have a better under-monitor hole cleaning is to take a look at the standingof LCM pluggingand hydrocarbonbehaviourshakers, to maintain a regular watch of solids phenomenain horizontalwell bores.concentrationin the mud (which is a good indica-tion of solids regrinding)and to make a massic Lost CirculationPluggingflow balance of solids control equipment, ratherthan relyingonly on theoreticalvelocityvalues. Plugging difficulties encountered in certainhorizontal drillings acrosa fracture-producingTable 1 gives a broad descriptionof which type of reservoirsled us to designa test set-upallowingtransportationwill take place in a section of the simulationof this type of loss for a better

annulus characterizedby its inclinationand the understanding of the phenomenon and to try toaverage flow velocity.This is purely a guide line provide a solutionto this problem.and only represents a synthesis of literature2,3,4, our experiments,and what we have suspectedduring the drilling of our horizontal and high * a certain amount of cuttings are transportedout of the hole as mud particleswhen erodeddeviatedwells. ** when the Ca r ryfn g ca pa cit y of the mud is not

sufficientand high concentrationsof cuttingsare generated in the annulus, these plugsrestrictthe flow paasage and are iiftedby thedifferentialpressurethrough them


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4 NIJDAND CEMENT FDR HORIZONTALWELLS 5PE 15

The first phase of testing,using mesns classically Remarksemployedin the field (60 kg~ms < LCM concentration[C] < 130 kg/m), showed that the upper half- The previousrecommendationsbring us to an impor-circumferencecf the well bore is not at all or tant conclusion: the high parametersused in suchonly slightly plugged, whereas the lower part is a procedurewill call for seriousprecautionssuch

regularlyplugged as shown in Figures 3.1, 3,2. aa turbine run-out,the runningdown of a specificpluggingstring,etc.1 Hydrocarbon in HorizontalWell BoresVarious solutions were then studied and a greatnumber of tests performed measuring the influence 1. Appearanceof Hydrocarbonsin the StaticMudof the followingmain parameters: Phase

choice of LCM (granulometry, ahape, density On all drilling sites, reference is commonlycontrasts,etc.), made to the gas bottom plug when drillingisresumedafter a round trip, i.e. a long staticrheologyof the base mud, periodof mud in the well servingto provideacertainback pressureon the reservoir.

- LCM concentration[C], This phenomenonexists even thoughPB is often- placementflow regime. greater than PR. The capillary forces arethen apparently not sufficient to avoid anIn this way, a certain number of interestingideas exchange simply due to the density unbalancewere developed,likely to help solve often specific of the fluids present, at equal pressure atproblemsencounteredin the field. the point of contact : hydrocarbon densityd < mud density .

E % Schematicallyspeaking,1. Light LCM, by floating,ought to have countered t e lighterpaases a ove the heavier.the effect of gravity previously encountered,but unfortunatelymost typeswere unsuitablefor A horizontal well bore will then favorizethis type of loss. LCM shape and granulometry this phenomenon in as much as the exchangeshouldbe chosen as far as possibledependingon surface is infinitely greater (lower half-formation and type of loss. In our own parti- cylinder)and due to the fact that the permea-cular case, it turned out that granular LCM bilitymay be of the fracturetype.alone vas relatively inefficient (e.g. CaCo340 Mm, etc.). However, granular, fibrous, e.g. Surfacearea of the bot~omof an 215,9 mmlamellar mixtures gave excellent results. (8 1/2)hole : 366 10- m2Finally, the solution to fracture enlargementwas found by simply adding elements of similar Surfacearea of the horizontalprojectionsize to that of the fractureitselfto the basic of a 300 m long 8 1/2 wellmixtures, these elements then serving as a bore : 65.5 mz.support structurefor LCM. A number of laboratory experiments enabled2. As the supply of LCM to the upper part of well this phenomenon to be demonstratedand alaobores by floatingproved unsuccessful,we found showed the importanceof the density unbalancethe followingsolutions(Fig. 4.1, 4.2) : as may be seen in Figure 5. Thus for anidentical reservoir fluid, the back pressureon the one hand theologicalmodifications,byincreasing exerted for the same vertical height willthe carrying capacity of the increasewith increasingmud density, and yetfluid : yield value YP > 20 lb/100 ft2 the exchangewill occur more rapidly and flowplasticviscosityPV > 30 cp, :atewill be higher. Likewise, if the reser-voir fluid happens to be gas, the density- on the other hand statistically,by increasing unbalance will be very great and the pheno-the chances of LCM passing along the upper menon will be accentuatedeven more.part of well bores by increasingLCM concen-tration [C] > 150 kg/ins. Therefore,a sub-hydrostaticreservoirmight,in certain circumstances (high permeability,3. The two previous ideas are the most important fracture permeability,no cake, etc.), yieldand plugging was achieved regardleas of the in staticphase. To make the mud heavier mightplacement regime. But it is interestingto note even be dangerous in this case, having thethat the slower the placement regime, the less opposite effect to that desired. A bettertime is needed for plugging. This is highly solutionwould be to form a relativelyimper-

advantageouain the field,where flow rates tend meable cake or to plug fissures aa seento be reduced to avoid any furtherdeterioration previously.of the situation.Finallyp a number of squeeze placement teatashowed that for rapid reaulta, the above-men-tioned conditions would have to be increasedeven further : equivale.,trheology but withhigher LCM concentrations, [C] >200 kg/ins.


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,.-,- l C,.,,. rh mmnn Ph. CFflR12FS. M. MARTIN>r~ L21+c2w -,, . -, ,..?.- , -,, --------- ,.. .

2. Evacuation of Gas Accumulated in a Horizontal CementingOutfitsWell Bore The cementingplugs (w?perplug + pump-downplug)Kicks during drilling or round trips will and check valves were tested on a 300 m long testcause points of hydrocarbon accumulation in bench in a 177.8mm (7)casing.overgauged zones, in high points, even in thebottom of the well bore if this is a high A classicalliner cementingwiper plug was circu-point. This phenomenon will be even more lated over more than 900 m (2,950ft) in waterworrying and difficult to deal with as the gas (no lubrication of the inner walls of the 7in question will not expand, being at equal casing), ti.ndhen a pressure5test was performedpressur2. correspondingto P = 50 .10 Pa. No leakagewasobservedand there were no signs of abnormalwearW[:carried out tests to study the behaviour of after dismantling.However, use of a float shoethese accumulationsduring annulus circulation or float collarproved inconclusive.of various drillingfluids. The sealingqualitiesof these systemsare unre-By simulating overgauged holes and a slight liable due to the relative or total lack ofangle (91 to ?2), regardless of the fluid annulusback pressureat the end of cementing.It(water, low rheology mud, high rheolok~ mud), is therefore safer to use spring-loadedvalvesan annulus velGcity greater than approximately (e.g.flappervalves).30 m(mn is sufficient to systematicallyevacuate the trapped gas. For lower flow rates Free Waterof below 25 mlmn, flu~ds with W < lb/100 ftzand PV < 10 cp do not manage to tOtallY The developmentof slurries without free waterevacuate these accumulations. The logical was extremelyimportantaa the appearanceof suchconclusion may therefore be drawn that the a phenomenonin horizontalsituationsresults inhigher the flow rate andlor rheology, the the formation of a water drain along the upperbetter the evacuation. Finally, a few tests part of the annulus. This drain calla for awere carried out for rising well bores at complete rethink on the seal required by cemen-approximately 100 These tests showed that ting. In fact, full-scale cementing tests withwhile at 90 the bubble moved at the same slurries not perfectly meeting this free waterspeed as the drilling fluid, at 100 this cancellation criterion ahowed not only thespeed was around 10 times slower. Thus~ for accumulationof water on the upper part of the215,9 mm (8 1/2) pipe annulus circulation at bore, but also migrationof this water along the60 m/mn in a 300 m long well bore at 100, the bore towardsthe high points of the annulus (thefluid would take 5 mn to travel the whole test benches presented inclinations varyingdistance, whereas the gas would only be between 88 and 920). Thus, a slurry with 0.5 cmevacuatedafter approximately45 m. API (0,2 %) free water in a 177.8 mm/254 mm(7/10)nnuluswould result in a water drain ofHORIZONTALCENENTING from 2 mm to more than 1 cm. Numerous possiblesolutionswere tested,often dictatedby tempera-As in vertical wells, good cementing of produc- ture, in three directions:tion casings in horizontalwells often results inimprovedyield (insulationof water in flow zone,

varying permeabilityzones, etc.). A long research - aid to rapid hydrationand aluminatecrystalli-program was undertakenon the feasibilityof such zation by the addition of certain diapersantscementing with the main aims being to solve creating oversaturationin sulfate ions. Thespecific problems posed by horizontality, to combinedaction of sulfate and aluminate formsunderstandthe influenceof each parameter,and, as ettringite, a veritable support structurefar as possible, to perform surf:(cetests at or between the grains of cement. When possible,near scale 1. the addition of CaCl forma the same type ofsupport structure an~ thus prevents aedimen-The principal preoccupationswere thus concerned tation :with : viscosificationof interstitialwater, e.g.the reliabilityof cementingoutfits, with latex emulsions,resulting in increasedwater pressure loss in the event of migra-the appearance and accumulation of free water tion,along the upper part of the well bore,addition of solid inert microelementswhich,- the best placementmethod(s), due to their very small size (10 to 100 timessmaller than a grain of cement) and large- trapppingand fingeringat the levelof reatric- number (representing5 to 25 % of the weighttions, of the cement), would occupy to a largeextent the gapa between the grains ofthe influenceof geometrichole accidents. cement and would greatly increase pressureloss in the event of interstitial watermigration.


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/ ham &Nn rFMFNT FnR HrlRT7flNTAlFIIS SPE 1546b ,= r!!. -- ,-. . . . . ..-. .--... ..- - -

Rheologyand Displacement(Fig.6.1, 6.2, 6.3) Unfortunately,horizontalwell drillir,gis oftendue to difficultpay zone characteristicsas hasNumerous 25 and 50 m (82 ft and 164 ft) teat alreadybeen underl~ned1. Consequently,the moatbenches and a 300 m (984 ft) bench allowed us to frequentlyused placement regime will be of theperform on the surface 177.8 mm/241.3mm S1OW flow type, thus avoiding the risks of(7/9 1/2)annulus cementing.We were thus able to fractureand lossesduring cementing.A number ofstudy the relative influenceof various parameters tests with poor centering,sloughing,etc, weresuch as centering, the presence of caving, etc.., carried out with slurries, high spacer densityfor suitabletheologiesand displacementregimes. with a length equivalentto approximately200 m(656 ft) of annulus, and a cement excess repre-A test bench w!:h variab?eannalar distanceallowed senting 100 to 150 m (328 ft to 492 ft) ofus, as will be seen later on, not only to study the annulus. Over-gaugi~g was well filled in, andproLlems of centering and fingering,but also the only a few highly restricted sections showeddisplacementof interfacesbetween mud, spacer a.ld intermittenttrapping (between 2 m (6.5ft) andslurry. In the case of turbulent displacement of 5 m (16.5ft) in length)on the lower part of theall three fluids or even for only the mud and well bore, insufficient to affect the overallspacer, excellent hole cleaning was observed. seal of the annulus.However, slow flow displacement showed the verygreat influence of the density unbalance para- CONCLUSIONmeter between the fluids.As soon as this unbalancebecomes large, a wedge phenomenon occurs during The aim of this paper is neither to solve nordisplacement both inside the casing and in the demistify the problems created by horizontalannulus, resulting in the heavier fluid passing drilling, which is no longer an extraordinarybelow the lighter fluid. If this phenomenon is practice. It is simply a presentation of ouradmissible for the mud-spacer interface, this is approach with regard to uud and cementing,not the case for the spacer-slurryinterface, as bearing in mind that today, cases of horizontalthe combinationof the two phenomena for a major drilling are guided by economic considerationscementjob could lead to pollutionof the cementby often related to difficult zones. Thus, ourthe mud or even trappingof the latter.This is why observationsat each well, our research,and ourwe opted rather for a relativelylong splcerdesign(200 to 250 m (656 ft to 820 ft) of anlulus,with practicalsolutionsto each new case that arises,have given us a know-how which will no doubtan intermediaterheology between that of mud and continue to evolue during future horizontalslurry, and a density near that of slurry. As in drillingjobs.vertical drilling, the casing string should beperfectly centered if a good cementationis to be ACKNOWLEDGEMENTobtained. The more the well is inclined, evenhorizontal,the less centeringand runningdown the The authors would like to thank Soci.5t6Elfcasing stringare compatible.However, restrictions Aquitaine and Institut FranCais du P6trole forprejudicial to correct mud displacementshould be permissionto publish this paper.avoi~,.das much as possible.Our researchled us totwo conclusions.On the one hand, a minimum annular REFERENCESdistanceis necessary,e.g. for a slow flow displa-cement regime, there should be a passage of at 1. Reiss, L.H. : Horizontal wells productionleast 2 x 2.54 cm 2 x 1 or even more to have any after five years, Society of Petroleumguaranteeof good cementing.Knowledgeof centering Engineers 14338,Las Vegas, Sept. 22 1985.reactions in horizontalopen holes being far fromcomplete,reducedcasingstringdiametersshouldbe 2. Tomren, P.M., Iyoho, A.W., Azar, J.J. : Anadopted for a given hole diameter. A 139.7mm5 1/2 liner will be preferred, for example, to a experimental study of cuttings transport indirectional wells, Society of Petroleum177.8 mm 7 or a 168.275mm 6 5/8 in a theore- Engineers12123,San Francisco,Oct. 5-8 1985.ticalhole of 215.9 mm 8 1/2 . On the other hand,even in the least favorable cases (casing string 3. Okrajni, S.S., Azar, J.J. : Mud cuttingslying on the bottom and slow flow displacement), transport in directional well drilling,fingeringwill remain very localizedas opposed to Society of Petroleum Engineera 14178, Lasthat occurring in vertical wells. Here too, the Vegas, Sept. 22-25 1985.effect of density is preponderantand will rapidlytend to close up trapping.Finally, not only will 4. Martin, M., de Lautrec, J., Marti-this fingering often stop in line with well-cen- gnon, A., : Essaia doptimisationdes carac-tered sections,but the ensuing passage of cement t6ristiques boues pour le forage dea puitswill tend to shorten it even more. horizontaux.Rapport Elf Aquitaine- InstitutFranGaisdu P6troleOctobre 1981.Armed with all the above knowledge,we carried outa great deal of annulus cementing on the surfaceand at scale 1, using both gel cement and neatslurries and displacementscorrespondingto rheo-logiea. With turbulentslurry regimes,mud displa-cement occurs perfectly and trapping at restric-tions or between shoe and well bottom (pockets)istotally cancelled out, but at the same time, theformulationof slurrieswithout free water is moredifficult.


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l:,!,lr 1 WE... !! ,, . .! ,!

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Fig. 3-l - Plugging zone with non sophisticated designLossesFlow t TF ,0,,~ L F

, / F

/

/ /

/ ) ~ F

f? , , : ;:;:;;,:!/// . .

K-. S.F. = S iO W f !O W/ 5 15 mnFig. 3-2 - Plugging curves with non sophisticated designVolume of Oil at surface

/! /111 /// / .tt/ /// // // /

Losses ),Flow rateS?E 15464

T F-------------------- -/

I f , IF =SF

Ivo 5 10 15

Fig. 4-l - Plugging agent concentration > 150 kLow rheology

LossesFlow rate

,,< /-/,/ /.+ /*,*, A , I > Hourso 24 50 100Complex brine d = 1,90

----- Satureted Na Cl brine d = 1,20Fresh water dl.Oil d :0,87

Fig. 5- Oil migration in static phase of dril ling mud

I

____ ~F//remnig. 4-2 - Plugging agent concentraikm > 150 kHigh rheology

Fig. 6-l - Cement slurry d = 1,90 slow flogood centralization

Fig. 6-2 - Cement slurry d = 1,90 slow f lbad centralization

oRis;;o..:.::.::i:J:/:.v*:.:,..Fig. 6-3 - Cement slurry d = 1,90 turbule

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E-Library15464 Mud and Cement for Horizontal Wells