Practice and understanding of efficient development of Deep CBM in Southern Yanchuan CBM field

Taking the practice of adjusting the development of Yanchuan South coalbed methane (CBM), the first medium-depth CBM field in China, as an example. Depth CBM is confronted with challenges of high reservoir non-homogeneity, single deployment mode of development well network, poor applicability of early conventional hydraulic fracturing, excessively long traditional drainage and extraction cycle, and large proportion of inefficient wells, etc. The exploration and practice of high-efficiency development and adjustment of Yanchuan South CBM Field provides a successful experience and technical reference for the effective exploitation of deep CBM in China. Practical research shows that: (1) Yanchuan South Deep Coalbed Methane Field has gone through three stages of development, including scale production, technology research, and innovation promotion. By deepening the research on the geological enrichment patterns of CBM, the geological understanding of the “Quadruple Coupling”for geological-engineering double-sweet-spot preferential selection has been formed. The concept of “effective support” was proposed innovatively, and key supporting technologies for reservoir reforming have been developed. The “four sections, three stabilizing and three controlling” technology of optimizing the production and discharge of mining has been established. The new technique shortened the average gas cycle from 240 d to 30 d. And the production of single wells has been greatly increased, with the daily gas production of directional wells reaching 2.0×10⁴m³ and horizontal wells reaching 6.5×10⁴m³. (2) Deep coalbed methane has strong non-homogeneity and difficult to develop effectively. The idea of overall development, batch implementation, integrated evaluation and construction, and rolling production construction is used to build production capacity. The Company constantly evaluates and adjusts the geological and technical double sweet spot areas, optimises the development plan in a timely manner, and effectively avoids the occurrence of low-efficiency wells in the batches. The economic impact of the programme has been significantly improved, with production rates increasing from 84% to 100%. (3) Based on the full life cycle of the gas reservoir, including well positioning, drilling and completion, reservoir stimulation, testing and production, and gathering, processing and treatment, the project adheres to the concept of geological-engineering integration and has formed a rational well spacing that matches the reserves, well networks and fracture networks. The reserve recovery rate of each well was increased by 30-50%. The project has established a fast and cost-effective drilling and completion technology, with the drilling speed increased by 34% compared to the early stage. It has also proposed a low-pressure gathering and processing technology involving "high-low pressure separation + three-stage boosting + inter-station connectivity", resulting in a 10.8% reduction in platform investment and a 20% saving in land use. The geological-engineering integration practice in the Yanchao South coal seam gas field provides technical support for deep coal seam gas development, and has good demonstration and promotion significance.