简介:Asinglesetofverticallyalignedcracksembeddedinapurelyisotropicbackgroundmaybeconsideredasalong-wavelengtheffectivetransverselyisotropy(HTI)mediumwithahorizontalsymmetryaxis.Thecrack-inducedHTIanisotropycanbecharacterizedbytheweaklyanisotropicparametersintroducedbyThomsen.TheseismicscatteringtheorycanbeutilizedfortheinversionfortheanisotropicparametersinweaklyanisotropicandheterogeneousHTImedia.Basedontheseismicscatteringtheory,wefirstderivedthelinearizedPP-andPS-wavereflectioncoefficientsintermsofP-andS-waveimpedances,densityaswellasthreeanisotropicparametersinHTImedia.Then,weproposedanovelBayesianMarkovchainMonteCarloinversionmethodofPP-andPSwaveforsixelasticandanisotropicparametersdirectly.Testsonsyntheticazimuthalseismicdatacontaminatedbyrandomerrorsdemonstratedthatthismethodappearsmoreaccurate,anti-noiseandstableowingtotheusageoftheconstrainedPS-wavecomparedwiththestandardsinversionschemetakingonlythePP-waveintoaccount.
简介: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.