四川盆地绵阳—广安浅水陆棚周缘上二叠统长兴组储层特征及主控因素OA

In recent years,significant breakthroughs have been achieved in the exploration of the Upper Permian Changxing Formation deep limestone reservoirs on the Mianyang-Guang'an shallow continental shelf in the Sichuan Basin,highlighting the immense natural gas exploration and development potential of this formation.However,the genesis and main controlling factors of high-quality reservoir development in this area are rarely studied,which restricts the exploration and development process.Based on the core,thin section and SEMobservations,and the cathodoluminescence and fluid inclusion analysis of key exploration wells,this paper clarifies the lithology,physical properties,sedimentary facies and storage space characteristics of the Changxing Formation reservoirs,and then analyzes the key diagenesis in the formation of the reservoirs and the pore evolution mechanisms.Additionally,the main factors controlling the development of deep high-quality limestone reservoirs in the Changxing Formation are identified based on the sedimentary facies-diagenesis-hydrocarbon generation coupling relationships.The following results are obtained.First,the Changxing Formation reservoirs are primaril developed in the pinnacle reef subfacies of shallow continental shelf and the bioclastic beach and biogenic reef subfacies of marginal platform,and lithologically dominated by bioclastic and biogenic reef limestones.Second,the storage space is characterized by secondary pores including intergranular dissolved pores,biogenic cavity dissolved pores,moldic pores,intercrystalline pores,and intercrystalline dissolved pores.Third,deep high-quality limestone reservoirs exhibit favorable physical properties,with moderate porosity(avg.12.21％)and moderate permeability(avg.5.15 mD),and their development takes dissolution the key diagenetic process.In conclusion,the high-quality limestone reservoirs of Changxing Formation in the Mianyang-Guang'an shallow continental shelf are under the joint control of three factors,with sedimentary facies belt laying the sediment foundation for reservoir development,diagenetic alteration controlling pore evolution,and hydrocarbon generation-diagenesis coupling and abnormal pressure ensuring pore preservation.The findings improve the theories on the development of deep carbonate porous reservoirs,and can provide important basis for regional oil and gas exploration.