Technology for efficient production of deep coalbed methane in the Shenfu block

Objective Deep coalbed methane (CBM), representing one crucial resource successor for ensuring the oil and gas security of China and achieving peak carbon dioxide emissions and carbon neutrality of the country, exhibits broad prospects for production. However, due to the small low universality of CBM production technologies under varying geological conditions, a technology that has been successfully applied in some blocks cannot be directly extended to other blocks. This leads to blind deployment of well types and well patterns in the early-stage exploration and development of new blocks to a certain extent. Given this, it is necessary to develop a suitable reservoir stimulation technology for efficient deep CBM production in the Shenfu block.

Methods First, based on the actual data of 79 production wells in the Shenfu block, this study compared the performance of vertical and horizontal wells from the aspects of production capacity and economic benefits. Second, taking the geological conditions of deep coal seams in the Shenfu block as input parameters, this study conducted a simulation analysis of the reasonable horizontal well length for deep CBM production. Last, by combining multiple disciplines such as geology, gas reservoirs, drilling and completion, engineering, and economic evaluation and taking the economic benefits per unit area as the goal of optimization, this study determined the specific technological parameters of reservoir stimulation for efficient deep CBM production in the Shenfu block.

Results and Conclusions The results indicate that horizontal wells are suitable for the production of deep CBM in the Shenfu block, with maximum economic benefits being obtained under a horizontal well length range of 800‒1500 m. Furthermore, the optimal well spacing, cluster spacing, and fracture half-length were determined at 300 m, 15‒20 m, and 120 m, respectively, corresponding to a total fracturing fluid volume ranging from 18000 to 24000 m³ and a total proppant volume varying between 2 500 and 3 500 m³. Based on these results, this study developed a set of reservoir stimulation technologies suitable for deep coal seams in the Shenfu block, with the core consisting of multiple clusters within a perforation section, shortened cluster spacing, high injection rates of fracturing fluids, fracturing and proppant transport via variable-viscosity slickwater, high-intensity proppant injection, propping of fractures on various scales, equal-aperture limited-entry perforating, creation of complex fracture networks. This study achieved the efficient production of deep CBM in the Shenfu block, providing a reference for the production of deep CBM in other basins of China.