Study On Lacustrine Carbonate Reservoirs In Shaojia Area

As an important reservoir,lacustrine carbonate rock is gaining more and more attention.During the deposition period of the upper fourth member of the Shahejie Formation,the eastern part of the Zhanhua sag was mostly alluvial alluvial plain.Only the area west of the isolated island was covered by lake water.The carbonate rock was only distributed in the west of the sag,mainly in the three areas of Yidong,Luojia and Shaojia.This paper mainly analyzes the sedimentary environment of reservoir development and the controlling factors of reservoir development from the regional tectonic background of Shaojia area,the sedimentary characteristics of lacustrine carbonate development and the reservoir characteristics,and then classifies and evaluates the reservoir and predicts Favorable zone.Through core observation and thin section observation under the microscope,the main rock types of carbonate rocks in the upper member of the fourth member of the Shahejie Formation in the study area are internal clastic limestone and biological limestone.The types of storage space are pores and fractures,among which secondary intergranular dissolution pores and algae lattice pores play a leading role.Sedimentary facies studies have shown that the upper part of the fourth member of the Shahejie Formation in the western part of the Zhanhua sag is the shore shallow lake subfacies and semi-deep lake subfacies.Sedimentary facies analysis was carried out by selecting the comparative profile of the continuous wells in the upper sub-segment of Shasi.It is found that the development of shallow lacustrine carbonate rocks in the Shaojia area may be due to the control of ancient sources.Through observation of ordinary thin slices and cast thin slices,the middle-low porosity and low permeability reservoirs in the study area were analyzed.The diagenesis developed in the study area mainly includes compaction and dissolution,dolomitization,cementation and dissolution.The control of reservoir quality by nearshore limestone beaches is mainly dissolution and dolomization.Dissolution and cementation in the high-energy area of the far-shore limestone beach dominate,and dissolution in the low-energy area is the main control factor of reservoir performance.The main controlling factors for comprehensive analysis of reservoir physical properties are rock type,sedimentary facies and diagenesis.Based on the geological characteristics of the reservoir,the favorable zone prediction is carried out.It is considered that the Yidong fault zone and the high-energy zone fault zone of the limestone beach in the far shore are good type ? reservoirs,and the limestone beach near the shore is controlled by dolomization and faulting.,Is a good reservoir of class ?,and the fault development zone of the low-energy limestone beach in the southeast is a favorable zone of class ?.