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1、Sand Exclusion and ManagementMBDCISand Controlor Sand Management?Maurice B. DusseaultSand Exclusion and ManagementMBDCIGoalsuTo develop a basic understanding of sand control and sand management physicsuTo understand the basic technical options for sand exclusionuTo explore completion and production
2、options other than sand exclusionuTo outline a decision-making environment for sand control and sand managementSand Exclusion and ManagementMBDCITwo Basic ApproachesSAND EXCLUSIONuScreened CompletionsScreens, filters, etc.Slotted linersGravel packsFrac-and-packuScreenless CompletionsOriented perfora
3、tionsGradient and rate controlHorizontal wellsOpen holes SAND MANAGEMENTuEncouraging sand influxHeavy oil productionCompletion approachuLiving with sand influxSand Management conceptEvolution of an oil welluDeliberate sand clean-upA workover and testing approach for wellsSand Exclusion and Managemen
4、tMBDCISand or No Sand?uThere now exist three possible routes:A: Totally avoid sand ingressB: Live with low rates of sand ingressC: Encourage sanding to enhance oil ratesuA: Total exclusion screens, packs, linersuB: Live with some sand better oil rates, but a Sand Management framework is requireduC:
5、Encourage sand has proven highly valuable in heavy oil development in CanadaSand Exclusion and ManagementMBDCIDecisions, Decisions, Decisions uQuantitative answers based on risk analysis, good data, and experience are required to make the best economic decisions.Sand Exclusion and ManagementMBDCIOpt
6、ion A: Sand ExclusionuWhen are total exclusion techniques necessary? (i.e.: when are quantitative predictions needed?)uExclusion must be applied when sand influx consequences are absolutely unacceptable:Usually in high-rate natural gas (high steel erosion)Inadequate facilities to handle the sanduHow
7、ever, exclusion costs money:Reduced oil production rateCAPEX (e.g. 1M$ for a North Sea gravel pack)Sand Exclusion and ManagementMBDCIOption B: Sand ManagementuWhen can we live with “some” sand?When oil rates are thereby enhancedIf sand management costs are modestIf well and facility risks can be man
8、ageduThere are costs and risks involvedAllowing sand influx is more “risky”Facilities modification requiredConstant surveillance is needed to manage riskuProbably inapplicable in high gas rate wellsSand Exclusion and ManagementMBDCIOption C: Encouraging SanduWhen do we want to produce sand?When prod
9、ucing heavy oil (CHOPS)As a completion approach (higher k)As a workover approach (eliminate “skin”)uThere are costs and risks involved, butNo choice in most cases (no sand-no oil)Sand erosion in heavy oil is minimalPumping problems have been solvedSand management costs 10-25% of OPEXSand Exclusion a
10、nd ManagementMBDCISanding and GeomechanicsuSanding is a Rock Mechanics IssueuThe important geomechanics factors are:uUnderstanding the physics is vitalu Completion strategy is vitaluWell management is vitalThe tensile and shear strength of the reservoirThe in situ stresses and pore pressuresThe hydr
11、odynamic drag forces on the matrixAlteration of rock properties (damage)Alterations of stresses and pressures with timeSand Exclusion and ManagementMBDCIEconomics and RiskECONOMIC FACTORSuProduction RateEffect of screens on QQ and reduction of p/ruCompletion CostsCAPEX for installing gravel packs, s
12、creensuIntervention NeedsFrequency of workoversScale and fines RISK FACTORSuSand erosion riskSurface facilitiesSafety issuesuWell impairment riskPlugging the well? Casing loss? uSand handling requirements Separation, storage, disposal$-$Sand Exclusion and ManagementMBDCIWhat the Industry NeedsuA sof
13、tware environment to make intelligent well completion decisions in sanding casesEconomic factors must be incorporatedA method of assessing risk in terms of $uAnalysis tools to support decision makinguHard data on costs and benefitsuA repository of practical experience in various areas, environments
14、(e.g. offshore)uA clear understanding of the physicsSand Exclusion and ManagementMBDCIGeomechanics Impact Flow PathSand Exclusion and ManagementMBDCICauses of SandinguPerforations damage the rock (next slide)uConfining stress are reduced ( no friction)uCohesion is destroyed, weakeninguThus, seepage
15、forces can pluck grains freeuAs “cavity” grows, high shear stresses on the walls lead to weakening and dilationuOnce the yielded zone approaches the size of the reservoir thickness, the high v aids the process Sand Exclusion and ManagementMBDCITypes of Sand ProductionuSand clean up after perforating
16、 before placing the well on productionuEpisodic sand bursts during productionuContinuous sand influx (heavy oil in UCS)uFine-grained particles migration through the formation matrixuDeliberate sand clean-up activities during initial completion or during a workoveruNew sand influx late in the well li
17、feSand Exclusion and ManagementMBDCIPerforation Clean-UpuPerforating damages the formationuGenerates crushed and disaggregated sanduOften in the form of an emulsionuClean-up is designed to remove this sandSwabbing (generating high p/r, F) Build-up of p, then sudden drawdownFlushing produced sand to
18、surfaceuBut! - Real-time measurements are difficult, and field control almost impossibleSand Exclusion and ManagementMBDCIDamage From Perforatingintactweakened“remolded”shearstressnormal stressstrengthplotsloss of tensile strengthwellweakeningUsing a Mohr-Coulomb strength plot to illustrate damagepe
19、rforationSand Exclusion and ManagementMBDCIFines MigrationuThe matrix stays intact, but small interstitial clay and mineral grains are mobilized by:High local gradients at pore throatsGeochemical alterations (waterflood, T)uFines tend to block the well, plug screensuQ, p/r , & more fines are mobiliz
20、eduSerious fines problems tend to lead to many workovers, chemical solutions (acids)u“Living with” fines is an attractive solutionSand Exclusion and ManagementMBDCIFines ProductionThroat blockageFines mobilized by: geochemistryp (drag force)sand strainsclaysgrainsFines are less than 1/20th mean grai
21、n sizeSand Exclusion and ManagementMBDCIContinuous Sand InfluxuUsed in CHOPS (Cold Heavy Oil Production with Sand, m 50 20,000 cP)uA valuable, low-risk production strategy in UCS with viscous oils and gas in solutionuEntire matrix is produced (not only fines)uTypical rates are from 0.25 to 10% sand
22、by volume of the dead liquidsuSanding increases well productivity, eliminates fines or asphaltenes blockagesuMust cope intelligently with sandSand Exclusion and ManagementMBDCIContinuous Sand ProductionYielded and channeled zone generated by large-scale sanding Heavy oil UCSAs much as 10% sand by vo
23、lume liquids Sand Exclusion and ManagementMBDCIIntermittent Sand BurstsuOccurs in poorly consolidated sands, perforated high rate oil and gas wellsuBursts are “self cleaning” events, and tend to remove near-well flow impediments (“skin”)uBeneficial effects on Q, fewer interventionsuLower CAPEX for w
24、ell completionsuHigher risks because of episodic sand influxuFacilities must be designed to handle sandSand Exclusion and ManagementMBDCISand BurstsuSanding in high rate oil wells in poorly consolidated sandstones comes in “bursts” A burst may be from a few kg to as much as 100 kgmini-burststimesand
25、 rate,g/m310-100 minsharp rise timeslow decayBursts may occur every few days to every few weeksSand Exclusion and ManagementMBDCIClean-Up and Well TestsuDeliberate aggressive clean-up carried out on wells suffering from productivity lossesPressure build-up (skin assessment)Aggressive drawdown to gen
26、erate sand burstsPeriod of productionBuild-up again, drawdown, produceRepeat 3-4 times and study skin dropuThis methodology carries little risk, only time, and in the right candidates, QSand Exclusion and ManagementMBDCILate Well Life SandinguCaused by stress changes from depletionSand fabric is dam
27、aged by high Cohesion is reduceduCaused by phase changes (capillarity effect)Water influx so that Sw increases locallyuCaused by operators trying to maintain QoilIncrease in p, sanding triggereduAn oil well in a UCS changes its behavior over its life time, souWell management strategy changes neededS
28、and Exclusion and ManagementMBDCIProblems With SandinguWellbore sand flow and blockage risks uErosion of downhole screens, devicesuErosion of surface goods and safetyuSand separation technology issuesuSand disposal or sand clean upuParticular horizontal well issuesBlocking at the toe (sand dunes in
29、low parts)Difficult and costly cleaningWe can handle some but not a lot of sandSand Exclusion and ManagementMBDCIThe Seepage Force on GrainsuThe hydrodynamic or seepage force FFree flow in perforation channelporous medium flowpSeepage Force = F = sAwp/lp + pp + pp + pThe pressure gradient leads to a
30、 seepage force that destabilizes individual sand grains or groups of grainsFSand Exclusion and ManagementMBDCIHydrodynamic Drag (I)uAlso called “seepage force”uResults from p, is proportional to gradientuA = cross-sectional area of grain or “chip”uw = a measure of grain diameterus = a shape factor t
31、o account for geometriesuGradient is directional (vector), F is coaxial to the gradient directionSand Exclusion and ManagementMBDCIHydrodynamic Drag (II)uTo reduce force, reduce the gradient!uAt a grain or fragment level, this is very difficult to quantify rigorouslyThe geometry must be specifiedGra
32、dients fluctuate locallyIt is independent of velocity for Darcy flowTurbulence can change drag forceOther complicating factors can arise in practiceuThus, some “continuum approach” is neededuDebate continues on which method is bestSand Exclusion and ManagementMBDCIConditions Around a Tunnelconvergen
33、t flowspallingdamagedrockFFqrseepage forceRock matrixRock matrixPerforation tunnelSand Exclusion and ManagementMBDCIPerforation Tunnelr = 0Zone of highest seepage forceDamaged zone (low c)Intact formationConvergent flow regionFlow linesCased, cemented wellSand Exclusion and ManagementMBDCIRock Stren
34、gth ConsiderationsuIf rock is very weak in cohesion, drag forces overcome the tensile strength at a free faceuIf the rock is weak in shear, higher stresses caused by drawdown can lead to shearing and loss of strength (cohesion damage)uChanges in H2O saturation destroys capillary cohesion (which acts
35、 as a tensile strength)uIf rock strength can be preserved, or even enhanced, sanding risk can be reducedSand Exclusion and ManagementMBDCIRock Strengthshearstressnormal stress - Mohr-Coulombplot of stressesRock strengthstrong rockweak rockc1c2Y1Y2Good cohesionPoor cohesion2143114Sand Exclusion and M
36、anagementMBDCISanding and Rock StrengthuUCS UnConsolidated Sandstone, is the usual sanding rock (+ Chalks)uThe strength of sand is related to its density and the amount of cohesion (cementation)uStraining destroys cohesion and also can lead to shearing, dilation, weakeninguIf a UCS remains well-conf
37、ined by stresses in all directions, it can resist thisuThus, good confining stress - 3 - is positiveSand Exclusion and ManagementMBDCIRock Strength (I)uIt is possible to reduce sanding risk by increasing the strength of the rockIncrease the cohesionIncrease the confining stressReduce the shear stres
38、suMany sand exclusion methods are based on these three basic conceptsuFor example:Fracturing increases the confining stress - 3Silicate injection increases the cohesionSand Exclusion and ManagementMBDCIRock Strength (II)uMethods to increase the strength include:uResin treatment of weak layers, squee
39、zesuPlacing gravel-packs to maintain 3uUse Frac-and-pack & other fracturing meth-ods to re-stress the sand and maintain 3uMaintain high water-flood pressures to avoid increasing , reducing 3, or losing cohesionuUse expanding screens to maintain 3Sand Exclusion and ManagementMBDCIWeakening of SanduDr
40、illing damage can reduce cohesion and cause dilation near the boreholeuPerforation damage can generate a large zone in which the cohesion is destroyed and the rock “granulated”uToo aggressive production can trigger disruption of fabric, weakened zoneuDepletion can change stressesuThermal shocking, h
41、igh p injection others? Sand Exclusion and ManagementMBDCIStrengthening Weak SandsuAdd cohesion, restress, minimize damageuCohesive methodsuRestressing methodsResin injection, several approachesSilicate injectionResin-coated sand use in fracturing and Frac-PackFracturingFrac-Pack methodsRadical idea
42、s (expand a steel liner in the wellbore?)Sand Exclusion and ManagementMBDCIScale Effects in SandinguThe stability of a cavity or weakened zone is a function of its radiusuSmall radius . successful archinguLarge-radius . arching less likelyuIf cavity grows, unstable sanding more likelyuHowever, large
43、 cavities also have lower exit gradients so F is lower!uClearly an optimization issue (how large?)Sand Exclusion and ManagementMBDCIPerforation Opening uScale effect is important as welluSmall openings have a better chance to develop a stable arch behind casinguLarge openings will tend to always hav
44、e the arch collapse under seepageuHow big? Roughness, packing density, angularity, are important (unquantified)poor arching better archingSand Exclusion and ManagementMBDCIScale Effects, Opening6DperfholecasingSand Exclusion and ManagementMBDCIScale Effects, TunnelstableunstableSand Exclusion and Ma
45、nagementMBDCIPerforating and SandinguDo you want to reduce the risk of sanding?uUse small diameter entry portsSand will form stable arches behind the casingSmaller diameter, the more stable the archuUse deep penetration chargesLarger flow area, lower local gradientsSmaller tunnel diameter, greater s
46、tabilityuReduce perforation densitySmaller damaged zones that do not overlapuOriented perforations in the stress fieldSand Exclusion and ManagementMBDCIReality of AnalysisuUncertainty prevails in geo-problemsuTrue “predictive” analyses are impossibleuDeterministic analyses are to “explore” sensitivi
47、ty, improve understandinguUltimately, a risk-based approach is essential, but still totally lackinguEmpirical correlations and “calibration” of models are used to improve predictability, and this is a “type” of risk analysisSand Exclusion and ManagementMBDCISand Exclusion CompletionsuOpen-hole compl
48、etion (-Y-Q analysis)uOH Gravel-pack or slotted liner, no cementuConventional perforated casing with:No sand exclusion devices or controlGradient or rate control to reduce sand riskScreen in the casingARCO-frac, Frac & Pack, resin sand.Gravel pack, inside or outsideResin, furan, other consolidation
49、methods highercost, lower riskSand Exclusion and ManagementMBDCIResin SqueezeLow k bed poor contactIntermediate k, OKHigh k, deep penetrationSand Exclusion and ManagementMBDCIChemical ConsolidationuEpoxy, furan treatment, silicate injection uAdvantagesLow risk if successfuluDisadvantagesCostly to pl
50、ace in long and horizontal wellsHeterogeneity causes placement problemsFlow rate reduction will occurFines, scale, asphaltenes can still block the welluShell uses epoxies in NigeriaSand Exclusion and ManagementMBDCISelective Resin SqueezeResin into troublesome zonePackerPackerUsed in wells on Sand M
51、anagement if one seriously troublesome zone must be isolatedSand Exclusion and ManagementMBDCISlots, Screens, Wire-WrappedCement Cement Open holeSlotted linerLiners are susceptible to scale and pluggingOpenings are sized and shaped using various empirical criteriaSand Exclusion and ManagementMBDCIOp
52、en-Hole & Liners, ScreensuPlacement of a sized (slotted) filter lineruAdvantagesEasy to place in long open holesGood sand exclusion is provideduDisadvantagesLiner can collapse (formation often does)Slotted liners often plug and develop scaleErosion of liners is commonAs always, reduction in PI usual
53、ly developsSand Exclusion and ManagementMBDCIScreens Inside Cased HolesCasing & tubingCarefully sized screen is placed inside perforated cased wellScreens are prone to scale, erosion, and plugging with fine-grained minerals, but intervention is relatively easySand Exclusion and ManagementMBDCIScreen
54、s, Slotted Liners, FiltersuPhysical exclusion of the particlesuAdvantagesSome fines can still flush throughReduces sanding risk to almost zerouDisadvantagesNot usually a selective process Usually reduces PI and susceptible to erosionProvides a substrate for chemical scalePore throat plugging not eli
55、minatedInterventions can be extremely costlySand Exclusion and ManagementMBDCIFracturing MethodsIncrease in3Fracture propped by resin-coated sandSand Exclusion and ManagementMBDCIFracturing Using Zone ExclusionIncrease in3Fracture propped by resin-coated sandVery weak, high-k sandResin-coated sandSa
56、nd not perforatedSand Exclusion and ManagementMBDCIPropped Fracture ApproachesuRe-stress borehole with fracture & proppantuAdvantages“Locks” sand by increasing 3, stops influxuDisadvantagesAs usual, PI often suffers (positive skin)Difficult in inclined wells (tortuosity effect)Premature tip screen-o
57、ut during placementFracture containment and placement controlProppant flow-back (use resin-coated sand)Sand Exclusion and ManagementMBDCIHigh Proppant Fracturingbottomhole pressurevirgin reservoir pore pressuretime (constant pumping rate)least principal stressProppant concentrationTreatment pressure
58、svertical stress“Frac-and-pack”Sand Exclusion and ManagementMBDCI!High Rate Fracturesproppant forced between casing and rock, sometimes called the halo effect, verified in 1999fat fractures,close to holecementcasing3extrawingsFrac & pack, high rate fracs, high m fracsq increases!r increases!Sand Exc
59、lusion and ManagementMBDCISelective PerforatingSensitive zone left unperforated; now, it cannot produce sandOften bad zone is high k zone as wellWell models cannot handle thisFull numerical model neededEconomic analysis is requiredFormation cross-flowSand Exclusion and ManagementMBDCISelective Perfo
60、ratinguAvoid weak zones likely to cause problemsuAdvantagesRelatively effective and economicaluDisadvantagesWeakest zone often highest permeability zoneTools to assess PI effect poorly developed yetProblematic in homogeneous reservoirsRock strength assessment is neededSand Exclusion and ManagementMB
61、DCIPhasing of Perforations3hmin=333hminHMAX112231 2 3PrincipalStressesWhich phasing to use?Sand Exclusion and ManagementMBDCISpacing of PerforationsFewer perforations:Higher p/r at each perf = greater sand riskNo overlap of damage zones = less sand riskMore perforations:Lower p/r at each perf = less
62、 sand riskOverlap of damage zones = greater sand riskSand Exclusion and ManagementMBDCIOriented, Phased PerforationsuPhased perforations in the best orientationsuAdvantagesUseful in cased cemented wells, reduces riskuDisadvantagesOrientation tool for perf placement requiredSand probability assessmen
63、t models are poorFull in situ stress mapping is neededField validation remains in its initial stagesReduces but does not eliminate sanding risksSand Exclusion and ManagementMBDCIPerforation StrategyuUse 180 phasing in the direction where stresses on perforation tunnel are leastuUse small diameter, d
64、eep penetrating charges: increases flow area, reduces port and tunnel diameter, favoring archinguPerforate a long intervaluPerforate selectively in reservoir sections least likely to become destabilizedSand Exclusion and ManagementMBDCIExpanded Screens, LinersqrqrUnexpanded screenr 0r 0Steel mandrel
65、Sand Exclusion and ManagementMBDCIExpanded Screens or LinersuSteel liner expanded against the holeuAdvantagesAdds radial stress with excellent effectsuDisadvantagesCostly, particularly in long horizontal wellsRelatively new technologyMetal screen is still prone to scale, pluggingSand Exclusion and M
66、anagementMBDCIExpanded Screen EffectYield criterionfor the sandstoneshearstress normal stress - Small +rSand far from shear or tensile failure after liner expansionSand near shear and tensile failureSand Exclusion and ManagementMBDCIOpen-Hole Gravel PackOpen casing or tubingPlaced gravel, D50 6D50 o
67、f sandAfter placement, intervention is almost impossibleGravel may tend to scale, perforations plug with finesCement Open hole may be reamed to larger dia.Sand Exclusion and ManagementMBDCIOpen-Hole Gravel PackuFilling the hole with a carefully sized graveluAdvantagesHighly effective in long horizon
68、tal wellsTechnology has improved greatly recentlyuDisadvantagesPositive skins (+5 - +10) always developRemoval impossible, chemical treatment hardRequires re-drilling a hole if blocksDoes not prevent fines and mineral scaleSand Exclusion and ManagementMBDCIInside-Casing Gravel PackOpen casing or tub
69、ingPlaced gravel, D50 6D50 of sandAfter placement, intervention is extremely difficultGravel may tend to scale, perforations plug with finesSand Exclusion and ManagementMBDCIInside-Casing Gravel PacksuEliminates sanding by placing granular filteruAdvantagesStops sand very effectivelyuDisadvantagesCo
70、stly and difficult to install properly, particularly in long horizontal & inclined wellsGravel often plugs and scalesFormation plugging is not eliminatedRemoving a pack or treating it is problematicPositive skin always develops (reduced PI)Sand Exclusion and ManagementMBDCIWell Placement to Avoid Sa
71、ndVertical fractures placed to overcome low kvlow klow kNeed good flow modelsNeed good fracturingBed susceptibleto sand productionhigh kkhkv?Sand Exclusion and ManagementMBDCIHorizontal Well PlacementuAvoid the sand producing layer entirelyuAdvantages:Sanding risk greatly reduced by avoidanceuDisadv
72、antages:uProblems if kh kv (e.g. if kh = 10kv)Only works if the weak layer is easily identified and consistent in the reservoirInstallation of vertical fractures is expensiveStill doesnt eliminate skin and scale problemsSand Exclusion and ManagementMBDCI Exit Gradient ControluThe greater the in-flow
73、 area, the lower the gradient to achieve a given flow rateuVarious approaches to lower gradient:Use a very long perforation interval, lower pUse a horizontal or steeply inclined well, lower pUse many narrow, deep penetration charges“Bean-up” the well conservativelyFractures reduce exit gradients (&
74、restress the sand)Displace gradients away from the sand free surfaceOther ideas? (e.g.: Cavity completion in Coal)Sand Exclusion and ManagementMBDCIReducing Gradientpressurer - distancewellboreortunnelpohighlow at the exit pointslow “bean-up” reduces exit gradients at early time, lower Fearly timela
75、ter timeSand Exclusion and ManagementMBDCISand Management IntroductionLearning to live with sand to increase profits in conventional oil wellsSand Exclusion and ManagementMBDCIIs Sanding Good or Bad?uIt may lead to well plugging, erosion, but:uIt almost always increases production (Q)!uThus, detaile
76、d cost benefit analysis is neededuSanding vital for CHOPuSand Management is now used in high-rate, conventional oil wells (higher Q, more $)uSurface equipment redesign implementeduProblematic if free gas is being producedSand Exclusion and ManagementMBDCILiving With Sand ProductionuNecessary in cold
77、 heavy oil productionuIn conventional oil, can we live with sand production? (Modest quantities only)uNew production system design (steel goods)uUse surface separators with back-pressure on the well to capture sanduMonitor steel goods, replace valves, etc.uNot yet suitable for subsea completionsSand
78、 Exclusion and ManagementMBDCIForces Promoting SandingwellborevHMAXhminIN SITUSTRESSperfdamaged rockconvergent flow(elevated dp/dl)Sand Exclusion and ManagementMBDCIDamaged ZonesuCohesion damageuIntroduction of a “flaw”uFocusing of flow pathscased holedrilling damagecementperforation damageSand Excl
79、usion and ManagementMBDCITensile SpallinguDamaged formationuReduced TouNo confinementuHigh gradients dp/dl lead to large forcesuSpalling takes placeuThe hole enlarges, becomes unstableconvergent flowspallingdamagedrockFHydrodynamic drag:FSand Exclusion and ManagementMBDCISand BurstsuSanding seems to
80、 comes in bursts: Is the sanding “event” a stable or unstable burst?A: unstable sandingB: Burst decays, stability is recoveredmini-burststimesand rate,g/m3Sand Exclusion and ManagementMBDCINature of Sand BurstinguSand does not enter the well continuouslyuThere are “mini-bursts” that are not detected
81、uThere are detectable bursts (clean-up events)They last 10 min to perhaps 100 minutesSand weight is perhaps 5 100 kg uSand burst peaks rapidlyuDecays to below detection limit more slowlyuWell returns to stable flow with little sanduWell skin has been reduced, PI goes up! Sand Exclusion and Managemen
82、tMBDCIOperating RangeConceptFlowRateSand StrengthMassive sanding?No sandingSand burstsSand #2Sand #1Upper limit dictated by safe operation or capacity of facilitiesSand-freelimit lineProductionenhancementQ1Q2Q3Sand Exclusion and ManagementMBDCIA Case History (North Sea)uSnorre Field, sandstonesuWell
83、 “A” throttled back to 2300 m3/d uGravel pack or other “cures” were assesseduSand Management protocols resulted in:No packs or screens whatsoever ($ savings)Oil rates of 3900 m3/d achieved ($ made)Minor sand bursts easily handled (low risk)Project costs paid for in one days oil!Sand Exclusion and Ma
84、nagementMBDCIDrawdown and Sanding-10-5051015202530050100150200250Maximum Total Drawdown (bar)Skin FactorNorth Sea Field “A”(18 wells):Trend line:Sand Exclusion and ManagementMBDCIA Case History (North Sea)Well Sand Clean Up (+44 % Oil)Sand Exclusion and ManagementMBDCISand Management, North Sea 0246
85、81012141600-20 20-4040-6060-80 80-100100-120120-140140-160160-180180-200Percentage IncreaseNumber (47 wells)Productivity Increase through Sand ManagementNorth Sea Field BThree platformsMean increase 36%Statfjord FormationSand Exclusion and ManagementMBDCI-ve Skin DevelopmentuSand bursts clean up wel
86、l more and moreuNo scale or asphaltene precipitation+100-5MONTHSSKIN NUMBER1234Typical well clean-up behaviortoSand Exclusion and ManagementMBDCISand ManagementuUsed in liquid-dominated production from relatively unconsolidated sandstonesuSanding can be controlleduSand bursts clean up the well regio
87、n of scale, fines, etc., = negative skins (-5 to -9)uMuch better production occurs ( +40%)uNo screens or gravel packsuGeomechanics assessment and monitoring!Sand Exclusion and ManagementMBDCIContrasting ApproachesuExclude the sanduReduction in PIuAdditional costsuNo sand to handleuPlugging can occur
88、uSkins values can riseuWell-understooduNo risk managementuManage the sanduPI goes up with burstsuNo pack or screen costsuSand handling requireduPlugging “self-cures”uSkin values drop (-ve)uNew technologyuRisk management reqdSand ExclusionSand ManagementSand Exclusion and ManagementMBDCIApplications
89、Areas for Sand ManagementuUnconsolidated and poorly consolidated SSuIn cases with no free gas in casing?uWhere oil rates can lift sand adequatelyuWhere sand grain size cannot block chokeuSeemingly, no depth limitation for thisuOffshore or onshore applications possibleuHorizontal wells must be carefu
90、lly assessedSand Exclusion and ManagementMBDCIWell Management IssuesuOther technologies still possible in a well using Sand ManagementuApproach may be valuable for several years, then another method installed if the well changes its characteristic behavioruSanding improves long-term PI, even in anot
91、her method is eventually installeduThus, Sand Management should always be considered as a primary alternativeSand Exclusion and ManagementMBDCISand Monitoring SystemAcoustic trigger detects sand burstFlow diverted to cyclone separatorSand quantifiedDecisions madeconventionalseparatorchokeacousticcol
92、larswellssandV/toilproductionsandV/tSand Exclusion and ManagementMBDCICore and Logging DatauTests on cores remain a vital data source for mechanical parameters, lithologyuCore data (granulometry, mineralogy) may tell where sand originatesuWell logs are the only way to interpolate mechanical data ove
93、r producing intervaluBehind-the-casing logs can identify zonesuNecessary for avoidance strategiesuStresses necessary for analysis, designSand Exclusion and ManagementMBDCISand Production PredictionsuWhen will sand influx begin?= (rock mechanics parameters: , Y, )= (completion, production approaches,
94、 k, po)uHow much will be produced? How fast?Assessment of sand management approachuConsequences of sand influx?On steel goods and system integrityOn oil production rateOn profits (CAPEX + OPEX)Sand Exclusion and ManagementMBDCIWhy Does Sanding Continue?uUnstable cavity created and propagates outward
95、s, large-scale stress redistributionuWell is drawn-down more and more aggressively to try and maintain QuSaturation changes may have an effect (most likely in fine-grained strata, North Sea chalk)u“Skin” removal (e.g. acetic acid) affects local cohesion, leading to instabilityuOther possibilitiesSan
96、d Exclusion and ManagementMBDCIWhy Does Sanding Stop?uA limited sanding zone is pinched offuGradients drop below the critical values as reservoir depletion continuesuSanding causes a higher permeability zone, displacing gradients from the welluA stable stress condition is achieved after the damaged
97、material is slowly removeduArching of cs.-gr. material behind perfs.Sand Exclusion and ManagementMBDCIToolkit for Sand ManagementuModels for onset of sandinguModels for rate of sand influx predictionuStrength models for overlapping perf zonesuSemi-analytic models: cross-formation flowuBetter well as
98、sessment models in generaluProtocols for special Sand Management testsSand-free rate testsSand clean-up proceduresSkin quantification testsSand Exclusion and ManagementMBDCISand Management ToolkituSand lifting capacity modelsuReliable sand detectors (downhole!)uInversion models for sand burst analys
99、isuSteel goods erosion models and monitoringuProtocols for well management decisionsuMethods to track well life quantitativelyuData bases for verification, risk analysisSand Exclusion and ManagementMBDCISand Signal Characteristicsdistance along well axis(Note: the same concepts apply for horizontal
100、wells)QZsanding bedcasing velocityor oil flow rateSand “event” just above perforationsEvent at surfacee.g. 30 second timeinterval, high amplitudee.g. 15 minute timeinterval, low amplitudeSand Exclusion and ManagementMBDCISand Clean-Up WorkoversuUsed to deliberately produce sand so as to remove near-
101、well blockages, open perfsuPressure build-up test, then rapid drawdownuHigh local p/r “pops off” blockagesuBuild-up tests allow assessment of skinuHas been very successful in the North SeauCan be used in combination with other workover approaches to improve Q, but generally cannot be used in screene
102、d wellsSand Exclusion and ManagementMBDCISand Clean-up Test1801601401201008060402012345Time,daysliquid rate m3/hrwellhead pressure - bardetectedsand bursts=1300 m3/dsand-freeflow rateRate - m3/hrSand Exclusion and ManagementMBDCIModeling NeedsuWe must predict:The upper, unstable limit where massive
103、sanding risk unacceptably highThe lower limit below which there is virtually no risk of sand influxQuantitative inclusion of CAPEX and lost oil costs associated with exclusionProduction rate or pressure gradientGeneralized strength measureequal riskcontoursweaksandstrongsanddoes increased production
104、 warrantspecial completions?Sand Exclusion and ManagementMBDCIGeomechanics Sanding ModelsuAccount for natural stressesuAccount for the strength of the formation sanduAccount for seepage forcesvHMAXhminIN SITUSTRESSnFSand Exclusion and ManagementMBDCICurves, Triaxial Testsstress difference1 - 3 axial
105、 strain -a peakstrengthseating, microcrack closure“elastic” part of curve massive damage, shear plane developsdamage startssudden dropcohesionbreakingcontinued damageultimate or residual strengtharr = 3 a = 1 max planesslipplanesaxial cleavageSand Exclusion and ManagementMBDCIRock StrengthuTo plot y
106、ield criteria from triaxial tests, on equally scaled axes, plot 1 and 3 at failure, join with semicircle: tangent = Y31YToncohesioncSand Exclusion and ManagementMBDCIMethods of Analysis (I)uAnalysis must be founded on a “conceptual” model which is adequate (good physics!)uEmpirical models are based
107、on practice and “qualitative” assessments uExperience is a powerful tool, and requires a strong intuitive understanding of physicsuAnalytical (closed-form) and semi-analytical models are sets of equations which can be solved directly (e.g. T or i,j around hole)Sand Exclusion and ManagementMBDCIMetho
108、ds of Analysis (II)uNumerical models are for complex geometries, non-constant boundary conditions, departures from linearity, coupling of processes (eg: flow + T + -)uDifferent approaches are best for different problems (FD for T, p; FEM for -, etc.)Finite difference formulations (FD)Finite element
109、approaches (FEM)Boundary discretization methods (BE, DD, BI)Discrete element methods (DEM)Sand Exclusion and ManagementMBDCIMethods of Analysis (III)uProbabilistic models use “sampling” techniques for the variables to study the probabilities of an outcome (Monte-Carlo methods)uStochastic models coul
110、d mean that properties are varied according to pre-defined distributionsuTo date, in Petroleum Geomechanics, these types of models have been sparingly used; generally, “deterministic” models are favoreduThese may be very important for risk analysisSand Exclusion and ManagementMBDCINew Completions Te
111、chniquesuUse slotted liners fitting in unperforated open holes (i.e.: much less damage)uFracture the well conventionally to restress the sand, reduce gradientuUse aggressive Frac-Pack approachesuProduce sand for a while, then recomplete with a Frac-Pack Gives a high-k zone near the well, lower gradi
112、entsRestresses the sandUse a resin-coated strategy to reduce flowbackSand Exclusion and ManagementMBDCIA New Completion ApproachCoarse sand placed by frac-&-packThe dilated and channeled region outside the frac-&-pack15-20 m?Sand Exclusion and ManagementMBDCIFormation Parametersrparameterpermeabilit
113、yaverage pore throat diameterporosityThe new method improves the formation characteristics around the well, reducing fines blocking, increasing the well productivitySand Exclusion and ManagementMBDCIHybrid CompletionuTest to determine if sand control necessaryuIf yes, continue the test and produce 2
114、0-30 m3 of sand from the formationuReduce flow circulate out sanduInstall a frac-&-pack in the wellbore, using more sand than normal to restress the zoneuTail in with 30% resin-coated coarse sanduShould not need screens, liners or sand exclusion methods thereafter, + more oil Sand Exclusion and Mana
115、gementMBDCIEconomics and RiskECONOMIC FACTORSuProduction RateEffect of screens on QQ and reduction of p/ruCompletion CostsCAPEX for installing gravel packs, screensuIntervention NeedsFrequency of workoversScale and fines RISK FACTORSuSand erosion riskSurface facilitiesSafety issuesuWell impairment r
116、iskPlugging the well? Casing loss? uSand handling requirements Separation, storage, disposal$-$Sand Exclusion and ManagementMBDCICompletion Approach HeirarchyuBased on strength, stress, Q, risk, $, etc.uVarious completion approaches possible:uOpen-hole (strong rock, relatively speaking)Uncemented li
117、ner (do strata collapse around it?)Perforations + Sand ManagementPerforations plus some exclusion method: gravel packs, screens, frac-and-pack, ARCO fracResin impregnation and re-fracturinguRational approach is to use geomechanics and risk assessment to find cheapest methodSand Exclusion and Managem
118、entMBDCIRisk Reduction ApproachesuOrient perforations in optimum directionuUse small port, deep penetration chargesuAvoid perforating intervals known to cause serious sanding problemsuA conservative staged production build-up may be used in sensitive casesuHorizontal wells (low entry gradients)uLong perforation intervaluOther methods
