Study On The Prediction Of Reef In Changxing Formation Of LHC Area In Eastern Sichuan

Carbonate oil and gas reserves account for more than 50% of global oil and gas resources,and most of the carbonate oil and gas are mainly distributed in reefs.Reef oil and gas reservoirs are an important lithologic reservoir.The Changxing Formation of the Permian in the Sichuan Basin is widely developed and has great potential for exploration.The reservoirs and the surrounding rocks have similar impedance values,and the conventional post-stack wave impedance inversion can not distinguish between the surrounding rocks.The results show that the reservoirs and the surrounding rocks have similar impedance values.And the reef reservoirs are relatively poor in the transverse direction of the reservoir and have a large variation in the longitudinal thickness.It is difficult to identify the exact time window when the fluid is identified,resulting in a lower accuracy of the reef fluid identification.In this paper,reservoir prediction and fluid identification of Changxing Formation reefs in LHC area of eastern Sichuan Province are carried out.Based on the investigation of technical methods and research results,this paper combine slogging,drilling,geology,earthquakes and predecessors Scholars on the eastern Sichuan Changxing group reef research,developed a targeted technical route.The main research contents are as follows:(1)The logging response characteristics,seismic response characteristics,lithological characteristics and physical properties of the reef reservoirs are analyzed and summarized in detail.(2)The LHC area of Changxing Formation reef identification model is established by using the seismic facies analysis method and seismic sedimentology theory;(3)In view of the difficulties in the identification of reefs and surrounding rocks in the study area,the reservoir parameters are optimized by the actual logging and drilling data,the natural gamma parameters have a good ability to identify high degree of albino reef reservoirs and muddy mud with high mud,and can identify the reef reservoirs accurately with wave impedance difference;(4)spectrum analysis technology for the reservoir section of the bypass channel spectrum analysis,combined with the domestic dual phase Media theory based on the Klinversion system for fluid identification,reducing the impact of the surrounding rock on fluid identification and improve the accuracy of biological reef fluid identification;(5)analysis of the seismic attributes of the reef identification and fluid identification capabilities,the study area root Amplitude attribute(RMS Amplitude)and instantaneous acceleration IAcc(Inst.Acceleration)have good recognition effect on the reef fluid;(6)In order to reduce the multi-solution and error of single attribute fluid prediction,two kinds of attributes of oil and gas-sensitive seismic attributes are selected to improve the accuracy of attribute fluid prediction.(7)Based on seismic inversion reservoir prediction,combine spectrum analysis technology and attribute ratio fusion comprehensive forecast,it is preferable to study the favorable area of Changxing Formation reef.Based on the actual data,it could be describe the distribution of the reefs in the Changxing Formation of the study area,and to effectively predict the distribution range of the reef favorable area in the Changxing Formation of the study area,which provides a strong support for further reef oil and gas exploration.But also provides a reliable reference for the study of the reefs of the Changxing Formation in the adjacent Permian.