Detection of gas reservoirs by the joint use of P- and PS-waves: A case study on the Ordos basin, China

(整期优先)网络出版时间:2009-03-13
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Wepresentanexampleofusingconverted-wavesforcharacterizingonshoregasreservoirsintheOrdosbasininNorthwestChina.TheOrdosbasinisthelargestgasprovinceinChina.Themaingasreservoirs(about3300mindepth)areinupperPaleozoicsandstonethathasloworreversedP-waveimpedanceandisimmediatelyaboveacoalseam.ThismakesitverydifficulttoimagethegasreservoirsusingconventionalP-wavedata.Analysisofcore,logandVSPdatashowsaweakPPreflectionbutarelativelystrongPS-convertedwavereflection,orbothstrongPP-andPS-reflectionsbutwithoppositepolarityfromthegasbearingsands,whichindicatesthepotentialofusingPS-wavestoimagethegasreservoirsintheOrdosbasin.Subsequently,thirteenseismiclineswereacquired,processedandinterpretedtoverifythePP-andPS-responses,andtwocorrespondingattributes(PP-andPS-amplituderatioandpolarityratio)areusedtomapthereser-voirsthroughjointPPandPSanalysis.