川西气田水合物防治工艺技术研究

CopyRight©2007LibraryofSouthWestPetroleumUniversity单位代码：10615西南石油大学硕士学位论文论文题目：川西气田水合物防治工艺技术研究研究生姓名：邓柯导师姓名：李颖川（教授）学科专业：油气田开发工程研究方向：采油采气工艺2007年4月25日CopyRight©2007LibraryofSouthWestPetroleumUniversityCopyRight©2007LibraryofSouthWestPetroleumUniversityI摘要川西气田在每年冬季和初春季节气井易生成水合物堵塞生产设备和管线，降低开井时率，严重影响气井正常生产。针对川西气田目前在井筒解堵过程中采用产量控制法存在储层伤害、影响气井产量，以及在集输管线解堵时采用高压管网气吹扫存在较大安全隐患、增加生产耗气等缺点。对生产年限较长的低压气井、井眼轨迹复杂、井筒内壁较脏的气井，以及新投产高压气井的水合物防治，本文开展了注醇工艺和井下节流工艺应用基础研究，在理论研究方面主要完成如下工作：1）在深入分析水合物生成热力学行为基础上，应用Du－Guo模型描述纯水体系水合物生成条件；针对含混合抑制剂（电解质和醇）水溶液体系，采用精度较高的JafarJavanmardi模型预测水合物生成条件，该模型在求解电解质溶液体系中水活度时，不需要进行复杂的闪蒸计算，同时考虑了含高溶解性的气体组份（如CO2和H2S）情况；2）本文建立了气井井筒及集输管线压力温度预测模型，在计算压力温度沿井深分布时，考虑了井筒与地层之间的传热，采用Ramey－Willhite井筒传热模型计算总传热系数；当井筒中下入节流器时，基于临界流动状态时气体嘴流过程的特性分析，建立了节流压降温降预测模型；3）应用天然气饱和含水量数学拟合方法，结合计算抑制剂最低液相浓度的Hammerschmidt经验公式，给出抑制剂合理注入量计算模型，用于注醇工艺参数设计。由临界流动时气产量与节流嘴径、嘴前后压力的关系式可导出节流嘴径计算公式。按照设计气产量和井口外输压力，运用基于径向传热的井筒压力温度耦合模型来计算节流嘴前温度，结合水合物生成条件、节流后气流温度，提出了适合川西气田、新的节流器下入深度计算方法，将上述理论和方法用VisualBasic语言实现，开发了水合物预测与防治应用程序。在工程应用方面，基于川西气田的生产特征，选取四口气井开展了注醇和井下节流工艺参数设计、现场施工。对联益101和105井进行注醇工艺设计，在对比甲醇和乙二醇抑制效果及经济效益的基础上优选出甲醇（工业酒精）作为施工药剂，并作出具体施工方案；通过对川孝452和马蓬43两口井的井下节流工艺设计，对该工艺适应性、工艺流程进行深入研究，并对节流后影响井口温度的诸多因素如节流器下入深度、井口压力等进行敏感性分析。通过现场应用，气井的生产压力及气产量保持稳定，生产形势良好，表明该两种工艺能有效防治水合物冻堵，保证了气井正常生产，提高了经济效益。关键词：川西气田，水合物防治，注醇工艺，井下节流，经济效益CopyRight©2007LibraryofSouthWestPetroleumUniversityIIABSTRACTAtfrigidwinterandspringprimeseason,gaswellsofWesternSichuanGasFieldprobablyformthegas-hydrate,whichblockupproductionfacilitiesandgatheringpipeline,itreducewellstartuptimeandseriouslyaffectregularproductionofgaswells.Atthemoment,WesternSichuanGasFieldmainlytakeproductioncontrolmeansandhigh-pressuregridgasscavenginglinemethodtopreventgashydrateblockageinwellboreandgatheringlinesepatately,manyproblemsarestillremains:harmingreservoir,affectinggasproduction,existingpotentialsafetyhazardandincreasinggasconsumption.Foreffectivelyprohibitingthehydrateblockageofgaswells,whichhavecomplexwellcourseordirtyinnerwalltube,orlongerproductionperiodandwhcihhavehigh-pressure.Thisarticledotheapplicationofbasicresearchesofalcoholinjectionanddownholethrottletechnologyrespectively.Intheorythemainresearchworkeshavedoneasfollows.1）Basedondeeplyanalysesingthethermodynamicsbehaviousofhydrateformation,usingtheDu-GuoModeltocomputethegas-hydrategenerationconditionforpurewatersystem.ApplyhighlyaccuracyJafarJavanmardiModeltopredictethehydrateformationtemperaturetogivingpressureforinhibiterssystem(electrolyteandalcohol),butnoflashcalculationalgorithmisneededforelectrolytesystem,whichcanbesuitfortheconditoncontaininghighsolubilitygasingredients,forexample:carbondioxideandhydrogensulfide.2）Thisarticleestablishtemperatureandpressurepredictionmodelsofwellboreandsurfacepipeline,whichconsidertheheattransferprocessbetweenboreholeandlayerwhencalculatepressureandtemperaturedistributionofentireborehole,usingRamey-Willhit’swellboreheattransfermodeltocomputetheoverallheattransfercoefficient.Whileplacingthebeanchokeinthewellbore,onthefoundationofperformanceanalysisforcriticalchokeflowprocess,suitablemodelcanbeseektocomputethechokedpressureandtemperaturedropingvalues.3）Applyingmathematicsfittingmeansofthegassaturatedmoisturechart,andcombiningHammerschmidtempiricequationtocalculateminimuminhibitor’sconcentrationinliquidphase,theappropriateinhibitorusagemodelcanbepresented,usingittodesignthealcoholinjectionparameters.Throughrelationalexpressionbetweengasflowrateandchokediameterandheel-and-toechokepressuresundercriticalflowcondition,calculationformulaofchokediametercanbederived.AccordingtodesignedwellflowratesandSWHP,onthegroundoftemperature-pressuremodelbasedonwellboreradialthermalconduction,couplinghyrateformationconditionandgastemperatureafterCopyRight©2007LibraryofSouthWestPetroleumUniversityIIIchoking,thisarticlebuildthenewcalculationmethodofchokesettingdepth,whichsuitedtoWesternSichuanGasField.UsingVisualBasic6.0softwaretocompilecomputerprogramsforforementionedtheoriseandmethods.Inengneeringapplications,basedontheanalysisofproductioncharacteristicsofWesternSichuanGasField,thisarticlemakealcoholinjectionanddownholethrottletechnologyparametersdesignsandsiteapplicationsoffourgaswells.DoingthealcoholinjectiontechnologicaldesignsforLianYi101and105.Comparingtheinhibitoryeffectandeconomicbenefitofmethanolorglycol.,methanol(industrialalcohol)betakenasexecutionmedicament,anddetailedconstructionschemebemaken.ThroughthedownholethrottletechnologicaldesignsofChuanXiao452andMaPeng43todeeplystudytheit’sadaptivenessandtechnologicalprocess,anddosomeresearchonthefactorssuchassettingdepthofchokeandwellheadpressure,whicheffectwellheadtemperatureafterchoking.Thefourgaswellskeepuppersistentproducingpressureandgasflowrateafterpractisingthistwohydratepreventionmeasures,whichdemonstratethatalcoholinjectionordownholechoketechnologycaneffectivelypreventhydrateblockage,guaranteeregularproductionofgaswellandimproveeconomicbenefit.Keywords:WesternSichuangasfieldhydratepreventionalcoholinjectiontechnologydownholethrottleeconomicbenefitCopyRight©2007LibraryofSo