Abstract:

:Inordertoidentifytheformationanddistributionofhigh-qualityreservoirunderconditionsoftightsandstonereservoirs,the distributionsandoriginsoftheanomalouslyhighporosityzonesoftheBayingebiFormationintheCretaceousintheChaganSagwere studiedbyusingthedataofmeasuredporosity,loggingporosity,thinsections,blueepoxyresin-impregnatedthinsectionsandSEM. Theresultsshowthattherearetwoanomalouslyhighporosityzonesatdepthsof1900-2300mand2500-3100m,respectively,withan averageporosityrangeof7%to5.2%.Thefirstanomalouslyhighporosityzoneismainlydistributedinthemiddle-shallowhorizons, andconsistsoffinesandstoneandconglomeratereservoirsthatweredepositedinthefandeltafrontoftheCentraltectoniczone.The secondoneisdistributedinthedeephorizons,andconsistsoffinesandstonereservoirsinthefandeltafrontofWulijitectoniczoneandEhensubsag.Theoriginofanomalouslyhighporosityzonevariesindifferenttectoniczones.Theoriginofhighporosityzoneisrelated totheleachingofmeteoricwaterinCentraltectoniczone,geothermalfluiddissolutioninWulijitectoniczone,andorganicacid dissolutionintheEhensubsag.

Key words: Anomalouslyhighporosityzone;organicacid;geothermalfluid;tightsandstone;BayingebiFormation;ChaganSag