Well Completion Methods and Practice of Fishbone Controlled Horizontal Well for CBM Mining

Through optimizing the design of CBM multi-branch horizontal well body structure, well completion process, well wall stability and pollution removal, and drilling mode, a new drilling and completion technology of fishbone controlled horizontal well and its supporting technology are proposed. In the field test, 9 wells were successfully completed by running casing or sieve tube, which fundamentally solved the problems of open hole section of multi-branch horizontal wells, such as easy collapse, easy blockage, undredging and no stimulation and reconstruction. The forward drilling method is conducive to the re-entry of main supports and the down-entry of completion string during drilling, and reduces the risk of branch wall collapse by optimizing drilling parameters and drilling fluid system. The structure of the dual well body realizes the overall hole diameter of the well, which is conducive to the later maintenance and operation. The conflict between borehole wall stability and reservoir pollution can be effectively solved by stabilizing the degradable drilling fluid system of borehole wall and the process of nitrogen gas lifting and washing wells and segmental reconstruction.