Research On The Reservoir Characteristics Of Tight Oil Reservoirs In The Jurassic Da'anzhai Member In Central Sichuan

The tight oil has gradually becomes another new target for the exploration and development of unconventional oil and gas all over the world.According to the results of previous studies,Da'anzhai member reservoir of Jurassic Ziliujing formation in central Sichuan Basin is rich in tight oil and has a vast prospect for development,but there are still some problems in the reservoir which is difficult to use effectively.The main issues include mismatch between resources and production,small diversity between reservoirs,difficult to identify the regularities of distribution of the effective reservoir,the conventional characterization technology of pore throat system was difficult to effectively reveal the characteristics of micro and nano pore throat and storage capacity.The theoretical direction of this paper is sedimentary petrology,petroleum geology,oil and gas reservoir geology,geophysical logging and the latest research both here and abroad.Further analysis the reservoir characteristics of the tight oil reservoir in the Da'anzhai member of Jurassic in the central Sichuan Basin from the characteristics of reservoir petrology,reservoir space,pore structure,physical property,control,source and reservoir relationship and regularities of distribution to laying the foundations for the development of tight oil in central Sichuan Basin.Analysis the reservoir characteristics of the tight oil reservoir in the Da'anzhai member of Jurassic in the central Sichuan Basin by means of thin section observation,lithological data analysis statistical,SEM,high pressure mercury injection,CT scanning etc.and combined with basic data such as drilling,logging,oil test and production dynamics.The results show that the rocks of the tight oil reservoir in the Da'anzhai member include grain limestone,argillaceous limestone,micrite shell coquina,micritic dolomite,mudstone and other like.The brittleness index of the grained limestone is the highest,followed by the bright crystal shell limestone.Dissolution pores and structural fractures are the main reservoir spaces and rich oil stored in various types of reservoir space.In addition,a large number of nanoscale pores and micro fractures play an important role in the formation of tight oil in the Da'anzhai member of Jurassic in the central Sichuan Basin.The reservoir of Da'anzhai member heterogeneous and physical property is very poor,the average porosity less than 2%and the permeability less than 0.1×10-3?m2.Research shows the pore structure of the reservoir can be divided into two categories and 8 small classes,reservoir physical properties were affected by pore structure,the combined model of reservoir and permeability has two kinds of isolated pore and pores-fractures,the reservoir space of different pore throat configuration types exists in three physical areas.Due to the factors of sedimentation,diagenesis and tectonic action,the difference of dynamic productivity of reservoir is greatly different.The source and reservoir configuration of the reservoir in Da'anzhai member divided into thick source-thick reservoir,thick source-middle reservoir,thick source-thin reservoir,thin source-thick reservoir,thin source-thin reservoir.The best of source and reservoir configuration is thick source-thick reservoir,secondly source-middle reservoir and thick source-thin reservoir is better types,the three types of source reservoir configuration all have more than ten thousand tons of industrial oil well.The results of the study show that west zone,sunken zone and part of the south zone have great potential for development.This study provides a reference for the evaluation and development of tight oil reservoirs in the central Sichuan Basin.