Characteristics And Logging Evaluation Of Tight Limestone Reservoirs In The Da'an Village Of The Jurassic In Central Sichuan

The Da'anzhai section of the Jurassic in the central Sichuan area is mainly composed of dense limestone reservoirs,which are affected by the destructive effects of diagenesis,such as compaction,recrystallization and cementation.The reservoirs are characterized by low porosity,low permeability,diverse pore structure and heterogeneity,resulting in complex reservoir structure in the Da' anzhai area,the type and characteristics of the hole inside the reservoir is changeable,which is not conducive to the exploration and development of dense oil and gas.Therefore,to realize the production in the central Sichuan area to be stable and yield,and it is of great practical significance to carry out the characteristics of dense limestone reservoir and logging evaluation.In this paper,the Da'anzhai section of Jurassic in central Sichuan is the research stage,the characteristics and types of dense limestone reservoirs are analyzed by core,ordinary flakes,cast sheet and rock experiment.Using the high-pressure mercury analysis the pore structure of tight limestone reservoir,and the physical and saturation models of the reservoirs in the Da' anzhai section of the Jurassic are established by using conventional logging data.In addition,based on the evaluation of reservoir space,pore structure and fracture characteristics,the physical limit of reservoirs is determined by empirical statistic method,pore structure classification method and capacity constraints,and then the characteristics of dense limestone reservoir type and logging characteristics are analyzed.Research shows:(1)The main lithology in this area is conquinoid limestone,which has high biodegradation content,mainly lake material such as ostracods,petal gills and gastropods,dissolution pore and microfracture are developed in the conquinoid limestone.(2)The storage space of the reservoir can be divided into three types according to its size,and the development of the micro-scale hole is more.The pore structure is dominated by the ? type,and has the characteristics of high discharge pressure,high median pressure,small pore throat radius and poor throat separation.The fractures are mainly medium-microcracks.The standard of electrical characteristics of reservoir characteristics is established by conventional logging.The pore and crack of micro-scale have a good response and good effect in resistivity curve.(3)The porosity and permeability of the reservoirs in the Da'anzhai section Jurassic in central Sichuan are 0.5%?1.5%and 0.001×10-3?1×10?pm2 respectively.The physical properties of the conquinoid limestone are better,and the physical properties of mud-bearing conquinoid limestone are poor.And the calculation model of reservoir physical properties and saturation parameters is established by using core hole permeability data and rock parameters.The results are obtained and the reservoir type can be analyzed more effectively.(4)Tight limestone reservoir was devided into four categories,among which the physical property of the class I reservior is the best,it was mostly development in the first members.Through the analysis of conventional logging characteristics,we found that when log facies is box type,it will mostly develop tnto class ? and class ?,when log facies is bell type,it will mostly develop into class ? and class ?,when log facies is funnel-finger type or tooth type,it will deveioped into class ?.(5)When the reservoir type division standard is applied to Zhongtai Mountain area,we found that the area around the SH2-SH6-SH1-SH4 in the first member,the SH2-SH6-N16-N1 in the first and third member,the ZHT1-SH2-SH4 and the N14-N13-N9-N6 in the third member belong to class I,and it will develop into a key area for exploration and development.In this paper,the characteristics of the conquinoid limestone of Jurassic Da'anzhai section in central Sichuan are studied,including reservoir characteristics,reservoir parameter calculation,reservoir type and reservoir logging characteristics.And it provide a more reliable basis for the exploration and development of the Da'anzhai section.