渝西地区志留系石牛栏组灰岩储层特征及有利储层形成机制OA

The Shiniulan Formation of the Silurian system in Western Chongqing overlies the Longmaxi Formation and exhibits significant exploration potential for near-source hydrocarbon accumulation.To explore new reservoirs and types of conventional gas in the Silurian system,it is necessary to further in-vestigate the characteristics and formation mechanisms of carbonate reservoirs in the Shiniulan Forma-tion in Western Chongqing,Sichuan Basin.Through comprehensive analysis of well cores,field out-crops,cuttings thin-section observations,reservoir physical properties and pore structure analysis(NMR T2 and mercury injection experiment),and rock geochemistry data(carbon and oxygen isotopes and trace elements)from the Shiniulan Formation,this study investigated the reservoir characteristics and re-vealed the synergistic influence mechanism of sedimentation-diagenesis to the formation of carbonate res-ervoirs.Key findings indicate that the main lithofacies of reservoirs in Silurian Shiniulan Formation is sparry bioclastic limestone,deposited in carbonate reef facies in the carbonate intra-slope belt whose for-mation controlled by sedimentation.The types of reservoirs are main residual primary biological pores and dissolved pores and fractures.The porosities and permeabilities are 2.00％-6.00％and(0.010-6.980)X 10-3 μm2 respectively.These reservoirs have undergone four diagenetic stages:syngenetic stage,penecontemporaneous stage,burial stage,and epigenetic stage.The precipitation and freshwater dissolution during both penecontemporaneous and epigenetic stages played constructive roles in the for-mation of carbonate reservoirs.The dominant controlling factors for sparry bioclastic limestone reser-voir development are identified as the favorable sedimentary facies combined with penecontemporaneous-epigenetic stage dissolution modified by precipitation and freshwater.This study identified the charac-teristics of the carbonate reservoirs in the Shiniulan Formation and the synergistic influence mechanism of sedimentation and diagenesis,providing a theoretical basis for efficient exploration and development of carbonate gas reservoirs in the Shiniulan Formation in Western Chongqing,Sichuan Basin.