Composite Coal Seam Multi-branch Horizontal Well Trajectory Optimization Design

The special geologic features of the coal-bearing pay zone group lead to thin coal seams,and the formation pressures on the upper and lower strata adjacent to the coal seam are independent.If mining is conducted for a single coal seam,the production is low and there is a lack of commercial extraction value.If multiple coal seams are used for integrated mining in an integrated fracturing manner,on-site practice indicates that there is a significant inter-layer interference phenomenon,which has a serious impact on the production life of wells.The development experience of foreign coal-bearing pay zone groups shows that the adoption of multi-branch horizontal well technology can effectively solve the current difficulties in the development of coal seams containing coal-bearing pay zones.This article will combine the rock mechanics,logging interpretation,mathematical model and other multi-disciplinary theoretical basis,on the basis of the actual geological data on the site,the optimal design of the multi-branch horizontal well trajectory of the coal seam with coal-bearing production layer group.Firstly,summarize the status quo of exploration and development technology of domestic coal-bearing paystone formations,conduct research on the status quo,define the wellbore structure design ideas for coal seams with coal-bearing strata,analyze the engineering difficulties and key technical problems in the drilling process,and summarize the horizontal The main factors that need to be considered in trajectory optimization such as segment orientation and horizontal segment length.Secondly,the site data were collected and the geological situation,lithology characteristics,stress distribution,and fracture development of the study area were statistically analyzed to analyze the accidental difficulties in the field drilling process.Again,according to the interpretation of logging data,the distribution characteristics of natural fractures in the study area are characterized,and the stress distribution model for the horizontal wells is established to provide the basis for optimizing the azimuth of the horizontal sections.Then,the relationship between the horizontal section and the production capacity is established based on the range of pressure drop spread in the horizontal section during the fracturing process,and the method for determining the optimal length of the horizontal section considering the friction of oil and gas is obtained.Finally,taking the multi-branch horizontal wells of the coal-bearing production group in the G-36 well as the engineering research object,according to the above research results,the application research on the optimal design of the wellbore trajectory for multi-branch horizontal wells in the coal seam-bearing formation group was carried out.The analysis shows that the horizontal well trajectory of the 8#coal seam branch is optimally located at 70° north west,110° north west,and 20° east east.The horizontal well trajectory of the 9#coal seam branch is optimally located at 10° in the west,170° in the west,and 30° in the east.By simulating the relationship between the branch lengths of 8#and 9#coal seams and the cumulative production,it can be determined that the branch length can be controlled at 200 meters to maximize the production capacity.According to the above methods and steps,a well-track optimization design scheme suitable for multi-combustion coal mining in the block is established.Through the above-mentioned theoretical research and analysis,the optimization of the wellbore trajectory of multi-branch horizontal wells in coal seams in the Linxing-Shenfu block has been optimized.The application results show that the research results of the paper have strong theoretical guidance significance for the efficient and safe development of the coal seam in the working area.