Study On The Control Of Shale Reservoir By High Frequency Sequence Of Wufeng-Longmaxi Formation In Southeast Chongqing

Based on the wavelet analysis of logging data,the high frequency sequence division of Wufeng Formation-Longmaxi Formation in the study area was carried out,the regional high frequency sequence stratigraphic framework was established,and the characteristics of shale reservoir development and the main control factors in the high frequency sequence were analyzed.The high frequency sequence stratigraphic framework of Wufeng Formation-Longmaxi Formation in the study area was established.On the basis of wavelet analysis of natural gamma data,the Wufeng Formation-Longmaxi Formation in the study area was divided into three tertiary sequences(SQ1?SQ2 and SQ3)and seven quaternary sequences(SQ1A?SQ2A?SQ2B?SQ2C?SQ3A?SQ3B?SQ3C).The sedimentary evolution characteristics of Wufeng Formation-Longmaxi Formation are discussed in the high frequency sequence framework.The sedimentary facies types of Formation-Longmaxi Formation in the study area include deep-water argillaceous shelf,shallow-water mixed shelf,shallow water arenaceous shelf,and shallow argillaceous shelf.The characteristics of shale reservoir in high frequency sequence strata are defined.The content of brittle minerals in shale reservoir is higher in SQ1A-SQ3 B,clay is the highest in SQ1A-SQ2 A,feldspar is the highest in SQ2 C and carbonate is the highest in SQ2 B and SQ2 C,all of which show the tendency of decreasing from deep to shallow in sequence.The law of TOC and gas content is consistent,with the highest in SQ1 A and SQ2 A.On the pore types,interbedded pores of clay minerals are more developed in SQ1 and SQ3,pyrite intergranular pores are the most in SQ3,and fractures are more developed in SQ1 and SQ3.Porosity,permeability is highest within SQ1 A and SQ3A?B in physical properties.In general,the content of organic matter and gas content of shale reservoir in Pengshui District is better than that in Qianjiang District than that in Youyang District,and the shale reservoir shows strong heterogeneity.The characteristics of shale reservoir development in high frequency sequence lattice are revealed,and the controlling effect of shale reservoir development is discussed.Shale reservoir development is mainly controlled by sedimentary environment,high frequency sequence and diagenesis,and deep-water argillaceous shelf is a favorable facies zone for high quality reservoir development.Sedimentary environment and high frequency sequence control the distribution of reservoir,organic matter content and distribution,the development of favorable reservoir is significantly related to transgression;physical source,sedimentary environment restricts the material composition of reservoir;mineral composition is closely related to specific surface area,porosity,gas content;shale reservoir has experienced compaction,cementation,dissolution,clay mineral transformation and organic matter thermal evolution,structural rupture and so on.The development mechanism of high-quality reservoir is discussed.