Study On Interpretation Method Of Deep Shale Gas Horizontal Well Logging In Southern Sichuan

The shale gas resources in southern Sichuan are abundant,mainly formed in marine and coastal sedimentary environments,and the porosity of deep shale is low and the permeability is small,but due to the particularity of the rock structure,the natural gas in it can exist and flow in the rock,forming high-quality reservoir conditions,most of which are buried at a depth of more than 2500 meters,and the total reserves are estimated to reach trillions of cubic meters.With the continuous development of shale gas field exploration and development,the southern Sichuan region has accumulated rich experience,the geological conditions are becoming more and more complex and the pursuit of economic development benefits is higher,and the application of horizontal wells is becoming more and more extensive.Taking the deep shale reservoir of Longmaxi Formation in southern Sichuan as the research object,this paper first investigates and analyzes the regional geological overview of the study area,combines the logging,geochemistry,physical properties and gas test seismic data to spread and predict the shale gas dessert space,uses the multi-well explanation software and the horizontal well logging explanation software to preliminarily establish the horizontal well and its guide hole spatial model in the study area,and analyzes the logging response of the horizontal well in the study area in combination with the dessert location study to understand the logging response characteristics of the horizontal well in the area.Then,the organic carbon content was calculated by the regression analysis method of △ lg R method and organic carbon influencing factor regression analysis method,and the correlation between organic carbon content and organic carbon content of 37 cores was calculated by the regression analysis method established by density and uranium content according to the accuracy display was 0.9862,the absolute error range was 0.04%-0.06%,and the root mean square error range was 1.08～3.12.The porosity interpretation model was established by using the acoustic time difference formula,density-neutron argillaceous correction method and regression analysis method of porosity influencing factors,and according to the actual data analysis of the well area,the correlation between density,uranium content and porosity was good,and the degree of consistency between the calculated porosity and core porosity was high,and the relative error was less than 8%.The influence of Langermuir parameters was used to establish the Langemuir parameter model and then calculate the adsorbed gas content,and the free gas content under formation conditions was determined according to the formation pressure and formation temperature,and then the total gas content interpretation model was established according to the adsorption gas content and free gas content,and the correlation between the total gas content and the porosity of core analysis was good,and the absolute error was 0.88%.The gas saturation was calculated by using the Simmen formula and the rock power parameters obtained by rock power experiments,and the absolute error of calculating gas saturation and core gas saturation was 1.86%.In the study of the engineering dessert parameters in the study area,the rock mechanics method was selected to calculate the brittleness index,and the absolute error of the brittleness index and core brittleness index when treating coring wells was 0.67%.The Young’s modulus interpretation method was established by the mineral composition method,and applied to the comparative analysis of the well treatment results and core results,and the absolute error was 0.79%.According to the fact that it is impossible to sample the core of each point in logging production,on the basis of considering manpower and material resources,the calculation method of static rock mechanical parameters is used to simultaneously select the longitudinal and transverse wave time difference to realize the dynamic and static conversion of the elastic modulus,and the elastic modulus is calculated and compared with the elastic modulus of the 38 sample data of the core,with an absolute error of 0.91%,which proves the feasibility of the method.In the process of establishing the in-situ stress interpretation model,the typical kelly model,Anderson model and Huang’s model at home and abroad are listed,and the Huang’s model is selected to calculate the in-situ stress under the condition of fully considering the calculation limitations and feasibility of the study area,and the absolute error between the maximum horizontal in-situ stress and the core level is 0.82%,and the absolute error between the minimum horizontal in-situ stress and the core level is 0.92%,which further explains the applicability of the in-situ stress calculation in the region.In the process of establishing the in-situ stress interpretation model,the typical kelly model,Anderson model and Huang’s model at home and abroad are listed,and the Huang’s model is selected to calculate the in-situ stress under the condition of fully considering the calculation limitations and feasibility of the study area,and the absolute error between the maximum horizontal in-situ stress and the core level is 0.82%,and the absolute error between the minimum horizontal in-situ stress and the core level is 0.92%,which further explains the applicability of the in-situ stress calculation in the region.Finally,the above logging interpretation method is used to process the logging data of11 horizontal wells in the study area,and the comparative demonstration analysis of 4 of them,the core data comparison table and intersection chart are listed,and the results show that the logging interpretation method has good application effect in deep shale gas in this area and meets the requirements of reserve calculation accuracy.