Eefficient fracturing technology and fine drainage system of ultra-deep coalbed methane in southeast Chongqing：A case study of NY1 well

According to the results of China’s new round of coalbed methane (CBM) resource evaluation, the CBM development mainly focuses on medium and shallow coal seams, and the geological conditions of deep-ultra deep coal reservoirs are more complicated. Thus, the reservoir fracturing technology and drainage management technology are two major factors in the development of CBM wells for deep coal reservoirs. In the area of southeast Chongqing, the coal seam of Longtan Formation is as deep as nearly 2 000 m, and there is no experience in ultra-deep CBM well development in this area. The NYI well is taken as an example, and its fracturing operation is completed according to the technical idea of large displacement, low sand ratio, pulsed and composite sand addition of different particle sizes by optimizing the fracturing process based on fracturing fluid system of drag reducing water. In the drainage, the method of segmented control, gradual speed reduction, timely adjustment, and low-pressure production is adopted to increase the flowback rate of CBM wells before gas breakthrough, extend the air supply radius as much as possible, and avoid the formation of velocity sensitive effect caused by large fluctuation of the liquid level and affecting the seepage channels of coal reservoirs. The results show that during the fracturing process of the NY1 well, the construction pressure is stable without sand plug occurring, and the daily gas production maintains at 2 800-3 000 m³ in the drainage. In the practice, the NY1 well has achieved high and stable production. The successful application of the fracturing technology and drainage system provide certain guidance for the theoretical research and development of ultra-deep CBM wells.