Diagenesis of the low-permeability sandstone reservoir of the first member of Shahejie formation in Gongshanmiao area and its influence on the reservoir property

Through the systematic study on the diagenesis of the studied reservoir,it is held that compaction,cementation,metasomasis and dissolution are its main diagenesis types,and that A phase of early diagenesis to B phase of middle diagenetic stage is its main diagenesis stage,and while B phase of middle diagenetsis is present diagenesis stage.The diagenesis series is of chlorite membrane on the surface of grain to and filling action of phyllipsite or analcidite to evident overgrowth of and emergence of authigenic quartz to frequent cementation,evident metasomasis and fairly obvious dissolution of ferrocalcite.Four dominant diagenetic facies (calcite or ferrocalcite cementation facies,zeolite cementation facies,chlorite-calcite cementation facies,rock debris-feldspar resolution facies) can be recognized in the reservoir.According to quantitative study on the diageneses of the reservoir,it is held that continuous compaction and intensive cementation are the main diagenetic factors of forming the low permeability reservoir.The dissolution of the third is main diagenetic factor of improving the property of the extra-low permeability reservoir,which appears more obvious in medium-size sandstone than in fine-size sandstone.