The Dominant Factors And Distribution Characteristics Of High Quality Reservoirs Of Qianfoya Formation Of Jurassic In Nanjiang-Tongjiang Area,Sichuan Province

The paper takes the Qianfoya Formation as the research object,through identification of thin sections,statistics of outcrop data,interpretation of well logging data,analysis of physical properties and mercury injection data.The results show that dominated rock types are lithic sandstones and feldspathic litharenite of Qianfoya Formation,and their sorting degree is medium to good.The porosity range is between 1%to 8%,and the permeability range is0.001×10^-3?m²to 1×10^-3?m²,that belongs to extremely low porosity and extremely low permeability reservoir.The reservoir space is mainly secondary porosity.The Qianfoya Formation reservoirs are divided into three categories.Based on the classification and evaluation of reservoirs,the standard of high-quality reservoirs in study area is defined,the porosity is greater than 4%,and the permeability is greater than 0.1×10^-3?m²as a reference value for definition.The factors affecting for the development of high-quality reservoirs in the study area are sedimentation and diagenesis.The sedimentation is the basis,which mainly affects the physical properties of the reservoir by controlling the compositions and structures of clastic rocks and sedimentary facies;the influence of diagenesis on physical properties is twofold,such as strong compaction,which has a destructive effect on the reservoir.Due to the development of dark mudstone and part of the coal-bearing strata in the study area,some layers have a strong dissolution effect,which greatly improves the physical properties of the reservoir and becomes one of the important factors affecting the formation for high-quality reservoirs.Based on the analysis of favorable sedimentary facies and diagenesis,the vertical distribution of high-quality reservoirs in the study area is mainly distributed in the second member of Qianfoya Formation,and a small part is distributed in the first member of Qianfoya Formation.The plane distribution of the high-quality reservoirs in the first and second member of Qianfoya is further analyzed,the first member of Qianfoya is mainly distributed in the Yuanlu 176 well,Heba 104 well and Jinxi 1 well;the second member of Qianfoya is mainly distributed in the Yuanlu 176 well-Yuanlu 175 Well-Yuanlu 171 well,Yuanlu 28 well-Yuanlu 3 well,Renhe 1 well-Chuanba 88well,Ma 1 well and Jinxi 1 well.