Discussion on the three-dimensional development model of the old well pattern in coalbed methane field

In order to increase the degree of production of CBM development blocks, when the production of a single well enters a decline period, the development plan needs to be adjusted, and the production increase and stability can be achieved through the measures such as layer adjustment or layer compensation. In terms of time, it is believed that the main coal seam should be developed first when it is put into production. After the decline period, the secondary main coal seam should be supplemented and combined; in space, combined with the development dynamics, the analytic hierarchy process is used to determine the main control indicators that affect the output and their weights, and then calculate the difference of each index for different coal seams, and after normalization, the distribution characteristics of the main coal seams in the well area are finely determined; the remaining reserves distribution characteristics are obtained by gridding geological reserves and produced gas. Finally, through the superposition of the main coal seam distribution and the corresponding remaining reserves distribution, the best development sequence is determined; and the fracturing and drainage technology is optimized for different development sequences. The proposed three-dimensional development method in the old CBM well pattern has achieved good development results in the Zhengcun well area of the Fanzhuang block, and finally realized the long-term stable production of the block and improved the recovery rate. For blocks with multiple coal seams, it is of significance for promotion.