Abstract:

Cretaceoussandstonesarecharacterizedbytheheterogeneity,thedifferentporosityevolutionprocessofdifferentdeposition settingandthedifficultyofthereservoirpredictioninHonghaoershuteDepression.Basedonthestudyofdepositionalcharacteristicsof theCretaceoussandstones,variousmethods,suchascorethinsection,castthinsectionandcoreobservation,areusedtosystematically studythediagenesisanditsinfluencesontheporosityevolutionprocess.Thereservoirs-qualityevolutionisstronglyinfluencedbythe burialhistoryanddiageneticeventsintheCretaceousofthemiddlesub-sagoftheHonghaoershuteDepression.Burialcompactionis themainfactorcausingthelossofporosityforthesandstones.Thecementsalsohaveaneffectonreducingthereservoirqualityofthe sandstones.Theacidicliquidrelatedtothehydrocarbon-expulsionoftheAershanFormationsourcerocksduringmesodiagenesis,have resultedindissolutionofthedetritalgrainsandcontributedabetterretentionofreservoirqualitytothesandstones.Thesandstonesof

thebraideddeltaarecharacterizedbyfinegrainsize,wellsortedandlowmatrixcontents.Theporefluidmaybeflowingintothepore spacesoftherock,whichleadstotheformationofsecondaryporosity.Thinchloritefilmarounddetritalgrainspreventedpartofquartz overgrowth,whichresultedinapartofprimaryporepreservationinthesandstonesoftheslumpturbiditefan.Attentionshouldbepaid to both the negative effects of compaction and cementation on the reservoirs and the positive effects of secondary porosity and pore-liningchloritecementindifferentsedimentarybackgrounds.

Key words: HonghaoershuteDepression;Cretaceous;sandstonereservoir;diagenesis;reservoir-quailtyevolution