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2页岩气的测井响应特征2.1页岩气的常规测井响应页岩气的常规测井响应主要包括页岩储层的自然伽马、井径、声波时差、中子孔隙度、地层密度、岩性密度和深浅电阻率等。吴庆红等(2011)研究认为斯伦贝谢公司于2004年开展了页岩气测井解释,建立了页岩气测井系列,包括自然伽马、补偿中子、补偿密度、电阻率、声波扫描、电阻率成像(FMI)、伽马能谱(HNGS)和元素俘获能谱测井(ECS)等,其中声波扫描、电阻率成像、元素俘获能谱测井是页岩测井的关键技术10。潘仁芳(2009)研究总结了对页岩气储层有效的测井曲线及对应的响应关系11,见表3。表3页岩气测井曲线响应特征(文献11)Tab.3Responsecharacteristicsofshalegaswelllogging(data11)测井曲线输出参数曲线特征影响因素自然伽马自然放射性高值(大于100API),局部低值泥质含量越高,自然伽马值越大;有机质中可能含有高放射性物质。井径井眼直径扩径泥质地层扩径;有机质的存在使井眼扩径更加严重。声波时差时差曲线较高,有周波跳跃岩性密度;泥岩页岩砂岩,有机质丰度高,声波时差大;含气量增大声波值变大;遇裂缝发生周波跳跃,井径扩大。中子孔隙度中子孔隙度高值束缚水使测量值偏高;含气量增大使测量值偏低;裂缝地区的中子孔隙度变大。地层密度地层密度中低值含气量大密度值低;有机质使测量值偏低;裂缝地层密度值偏低、井径扩大。岩性密度有效光电吸收指数Pe低值烧类引起测量值偏小;气体引起测量值偏小;裂缝带局部曲线降低。深浅电阻率深探测电阻率浅探测电阻率总体低值,局部高值;深浅侧向曲线几乎重合地层渗透率;泥质和束缚水均使电阻率偏低;有机质干酪根电阻率极大,测量值局部为高值。2.2页岩气的常规测井系列裸眼井测井常用三大测井系列、十一条测井曲线,可解决储层的岩性划分、物性评价和含油气性评价等。由于页岩气测井的特殊性,需要对常规测井系列进行方法组合优选。笔者认为,页岩气测井的主要内容应包括:岩性定性识别和定量评价、含气层的划分与评价、储集空间和渗流空间物性评价。开展页岩气测井的关键问题是,那里是页岩层、源岩有机质含量如何、页岩含气性如何、裂缝等储渗空间发育程度怎样。页岩气测井评价中,岩性定性识别和定量评价的常规测井方法主要包括自然电位测井、自然伽马测井和井径测井;含气层划分与评价的主要测井方法包括深浅侧向或深中感应电阻率测井、声波时差测井、密度测井和中子测井;储集空间和渗流空间物性评价的主要测井方法是声波时差测井、密度测井和中子测井。但页岩气测井值得指出,页岩气常规测井系列从方法上似乎涵盖了现代测井全部方法,方法组合和资料解释的侧重点却与石油测井有所不同。这与页岩气本身的特殊性密切相关。测井新技术中的核磁双Tw测井,进行差谱分析后,可根据差谱识别油、气、水层,对双TE测井进行移谱分析,可以判断气层。时间推移测井,下套管后最佳时间测量的中子与固井后24h内测量的中子曲线重叠,利用其差值可以评价气层2。2LoggingResponseCharacteristicsofShaleGas2.1 ConventionalLoggingResponseofShaleGasConventionalloggingresponsesofshalegasmainlyincludenaturalgammaray,welldiameter,acoustictime,neutronporosity,formationdensity,lithologydensityanddepthresistivityofshalereservoir.Onthebasisoftheresearchin2011,WuQinghong,etcthinkthatSchlumbergerCompanyhascarriedouttheloggingdatainterpretationofshalegasandhasestablishedloggingsuiteofshalegasin2004.Thisloggingsuiteincludesnaturalgammaray,compensationneutrons,compensationdensity,resistivity,soundwavesscanning,resistivityimaging(FMI),gammarayspectrum(HNGS)andelementcapturedspectrometrylogging(ECS)andsoon.Andamongthese,thekeytechnologiesofshaleloggingaresoundwavesscanning,resistivityimagingandelementcapturedspectrometrylogging10.In2009,PanRenfanghassummarizedtheloggingcurvesthatareeffectivetoshalegasreservoirandtheircorrespondingrelationshipsasshowninTable3.2.2 ConventionalLoggingSuiteofScaleGasOpenholeloggingusuallyusesthreeloggingsuitesincludingelevenloggingcurvestosolvetheproblemoflithologydivision,physicalparametersevaluationandoilinessevaluationofthereservoir.Becauseoftheparticularityofshalegaslogging,conventionallogseriesneedtobechoosedandcombinedrenewedly.Intheauthorsopinion,themaincontentofshalegasloggingshouldincludethequalitativeidentificationandquantitativeevaluationofthelithology,theclassificationandevaluationoftheaerationzoneandthephysicalparametersevaluationofthereservoirspaceandseepagespace.Theimportantproblemsofscalegasloggingarethesituationofshalestrata,organicmattercontentofsourcerock,gascontentofshaleandpermeabilityspaceabundanceofreservoir.Inshalegasloggingevaluation,theconventionalloggingmethodsofthequalitativeidentificationandquantitativeevaluationofthelithologymainlyincludenaturalpotentiallogging,naturalgammarayloggingandwelldiameterlogging;theconventionalloggingmethodsoftheclassificationandevaluationofaerationzonearemainlyincludedepthlateralloggingordepth-midinductionresistivitylogging,acoustictimelogging,densityloggingandneutronlog;theconventionalloggingmethodsofphysicalparametersevaluationofreservoirspaceandseepagespacemainlyincludeacoustictimelogging,densityloggingandneutronlog.Itisworthpointingoutthatshalegasconventionalloggingseriesseemstocoverallmodernloggingmethods,buttheemphasisofthecombinatorialmethodsanddatainterpretationofshalegasloggingisquitedifferentfromoilwelllogging.Thisisrelatedwiththespecialdensityoftheshalegasitself.MRIdoubleTwloggingisoneloggingmethodofofnewloggingtechnology.Thestepsofthisloggingmethodareasfollow:First,thedifferentialspectrumshouldbeanalsized.Second,accordingtothedifferentialspectrum,oil,.wanterandgasshouldbedistinguished.Third,theshiftedspectrumanalysistothedoubleTEloggingshouldbedone.Then,theairlayercanbeidentified.TimelapseloggingisthatairlayerisevaluatedbytheD-valueofdataoftheneutronmeasuredatthebesttimeafterrunningcasingandtheneutronmeasuredwithin24hoursaftercementing2.Tab.3Responsecharacteristicsofshalegaswelllogging(data11)LoggingCurvesOutputParametersCurvesCharacteristicsInfluencingFactorsnaturalgammaraynaturalradioactivityhighvalue(100API),partiallowvaluethehighershalecontent,thehighervalueofthenaturalgammaray;highradioactivematerialmaycontainedinorganicmatterwelldiameterholediameterholeenlargementholeenlargementofshalyformation;moreseriousholeenlargementbecausetheexistenceoftheorganicmatteracoustictransittimetimeequationcurvehigh,cycle-skipsexistinglithologydensity:mudrockshalesandstone,thehigherabundanceoforganicmatter,thehighervalueofacoustictransittime;thecontentofgasandthevalueofacoustictran
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