全国煤层气资源动态评价与可利用性分析

鄂尔多斯盆地东缘大宁−吉县区块深部煤层气勘探开发取得突破对煤层气产业带来重大影响，引起业内广泛关注和跟进。前期一些学者对深部煤层气勘探开发理论技术难点与对策开展了研究，但缺乏对典型气田开发先导试验系统总结。通过深入剖析深部煤层气地质特征与效益开发难点，总结大宁−吉县区块开发先导试验项目取得的进展和成效，明确开发规律并提出效益开发对策。结果表明：(1) 深部煤层具有广覆式发育、含气性好、游离气含量高、保存条件好、煤体结构好、脆性指数高、顶底板封盖性强等地质特征，但微构造发育、渗透性极差、矿化度高等因素制约了深部煤层气效益开发；(2) 不同地质条件下气井生产特征差异较大，通过先导试验落实气井产能和适应性开发技术对策，采用滚动开发模式可有效降低煤层强非均质性带来的开发风险；(3) 开展地质−工程一体化井网优化设计，构建井网与缝网高度弥合的人造气藏，可实现资源动用和采收率最大化；(4) “长水平段+多段多簇+大砂量”的大规模、大排量极限体积压裂技术可增大有效改造体积和井控储量，大幅提高单井产量；(5) 深部煤层气井具有“见气时间短、上产速度快、初期产量高、递减快”的生产特征，可实现短期快速规模上产，但气田长期稳产需持续新井投入；(6) 前期开发成本偏高，实现效益开发需不断提高工程作业效率、降低开发成本。综合认为，深部煤层气资源品质好，可动用性强，具备快速推广复制条件，大宁−吉县区块深部煤层气开发实践可为国内其他区块深部煤层气规模动用提供技术借鉴，对加快深部煤层气规模勘探开发具有重要意义。

Dynamic assessment of coalbed methane resources and availability in China

Breakthroughs in the exploration and production of deep coalbed methane (CBM) in the Daning-Jixian block on the eastern margin of the Ordos Basin exert a profound influence on the CBM industry, arousing extensive concern and follow-up. Although previous studies delved into the theoretical and technical challenges and corresponding solutions of deep CBM exploration and production, there is a lack a systematic summary of pilot tests for typical gas field exploitation. Through an in-depth dissection of the geological characteristics and challenges of cost-effective production of deep CBM, this study summarized the advances and outcomes of the pilot test projects in the Daning-Jixian block, determined the production patterns, and proposed strategies for cost-effective production. The results show that: (1) Deep coal seams exhibit extensive distributions, high gas content, rich free gas, favorable preservation conditions and coal structures, high brittleness index, and high sealing capacities of coal seam roof and floor. However, factors such as the presence of microstructures, extremely low permeability, and high total dissolved solids (TDS) content restrict the cost-effective production of deep CBM. (2) Different geological conditions result in significantly distinct production characteristics of gas wells. Therefore, by determining the production capacity of gas wells and the adaptive production technologies through pilot tests, the production risks caused by the high heterogeneity of coal seams can be effectively reduced using the progressive production mode. (3) Artificial gas reservoirs with highly bridged well patterns and fracturing networks, constructed based on the optimized geo-engineering integrated well pattern design, can maximize resource production and recovery. (4) The large-scale, high-injection-rate limit volume fracturing technology characterized by long horizontal sections, multiple sections and clusters, and large proppant volumes can increase effective stimulated reservoir volumes and well-controlled reserves, thus substantially enhancing single-well production. (5) deep CBM wells can achieve short-term rapid large-scale production growth owing to their production characteristics such as early gas production, rapid production addition, high initial gas production, and rapid decline. Nevertheless, long-term stable production of gas fields requires continuous drilling of new wells. (6) Given high early-stage production costs, it is necessary to constantly improve the engineering operation efficiency and reduce production costs in order to achieve cost-effective production. Overall, deep CBM resources, manifesting high quality and a production possibility, meet the requirements of rapid technological promotion and duplication. The deep CBM production in the Daning-Jixian block can provide a technical reference for the large-scale production of deep CBM in China's other blocks, holding great significance for accelerating the exploration and production of deep CBM in the country.