Research On Evaluation Technology Of Shale Gas Reservoir Of Longmaxi Formation In Zhaotong Demonstration Area

China's shale gas exploration and development is mainly concentrated in the Sichuan Basin and its surroundings,with the black shale of the Wufeng Formation-Longmaxi Formation as the main target layer.With the rapid rise of shale gas exploration and development,its testing technology and content have gradually become richer and more diverse,and its measurement accuracy has continued to increase.The experimental technology has developed in the direction of local microcosm and multiple methods.This article takes the Longmaxi Formation shale in the Zhaotong Demonstration Area as the research object,and studies the evaluation technology of shale reservoirs and its application in the study area.Based on field profile measurements,core observations,outcrops and core samples,X-ray diffraction analysis,field emission scanning electron microscopy,nano-CT,focused ion beam scanning electron microscopy,nuclear magnetic resonance,nitrogen adsorption,overlying pore infiltration,and ground A series of experimental technical methods such as chemical parameter testing,on-site desorption,and isothermal adsorption clearly defined the lithology,physical properties,geochemical properties,gas-bearing properties,and pore development characteristics of shale reservoirs in the study area.Then,by comparing each parameter with the gas content The relationship between them is studied on the influencing factors of shale gas-bearing properties.Finally,a multi-parameter combination evaluation method is used to comprehensively evaluate the shale reservoirs in the study area,and to classify the reservoir types in the study area.The main results show that the mineral composition of the Longmaxi Formation shale in the study area is mainly quartz,carbonate,and clay minerals,and contains a small amount of minerals such as feldspar and pyrite;the types of pores include intergranular pores,intragranular pores,organic pores,and Microcracks and nitrogen adsorption experiments show that the pore morphology is mainly parallel plate-shaped holes,tubular holes and ink bottle-shaped holes.According to BET and BJH theory,the total pore volume and total specific surface area of the Longmaxi Formation shale are large.Among them,Mesopores provide most of the pore volume.Micropores have the largest contribution to the total specific surface area.The pore size distribution is mainly micropores and narrow mesopores below 10nm.The porosity of the shale sample is determined based on the d V/d W pore size distribution of the sample.The types are divided into three types,corresponding to different organic matter contents.Among them,the TOC value and gas content of the shale at the bottom of the Longmaxi Formation are high,and the organic matter types are mainly type?and type II₁,which are in the stage of mature to overmature evolution.Overall quality is better.By studying the conditions of shale gas accumulation,and referring to the evaluation indexes and standards of shale gas reservoirs at home and abroad,the paper superimposes the four main parameters of organic matter content(TOC),porosity,formation pressure,and gas content,and integrates them.Considering shale thickness,burial depth,sedimentary facies zone,organic matter maturity(Ro)and other relevant parameter indicators,a shale gas reservoir evaluation system suitable for the study area was established,and the shale gas reservoirs in the study area were divided into 4 categories.It will provide a reference for the next exploration and development of shale gas in this area.