Study on technology of horizontal wells and vertical wells coupled depressurization in high rank coalbed methane

Low production and low efficiency area in high rank coalbed methane widely exist, which has already become one of the main bottlenecks in restricting the development of coalbed methane industry in China.In this study,the development of Zhengzhuang Block in Qinshui Basin of Shanxi Province was taken as an example.The reasonable development technology policy was studied using dynamic analysis and numerical simulation techniques. In view of the fact that the well spacing in this area was too large and the actual utilization of individual well was low, it was impossible to solve the problem of low production due to cooperative pressure reduction between wells.Utilizing the technical advantages of horizontal wells to develop CBM, the horizontal well- vertical well coupling pressure reducing activation technology was proposed innovatively. By interleaving series of cross-boreholes with vertical well fracturing cracks, the fractures in the coal seam were connected, largely improving the fracture diversion capability, and realizing coupling of the pressure between horizontal and vertical wells. Then the low-production vertical wells were revitalized.Research shows that this technology has acquired significant achievements in the Zhengzhuang Block. The average production of four infilled horizontal wells is 4 849 m3/d with stable production. Besides, adjacent vertical wells are activated. The average increasing production is 580 m3/d.The reserve productivity and recovery degree of the block are improved effectively.It is recommended to use this technology in the low production and low efficiency areas in high rank coalbed methane wells, which can effectively improve the recovery degree of geological reserves and activate inefficient old wells.