Jidong Oilfield Company, PetroChina
School of Energy Resource, China University of Geosciences (Beijing)
Coal Reservoir Laboratory of National Engineering Research Center of CBM Development & Utilization
Frontiers Science Center for Deep-time Digital Earth, China University of Geosciences (Beijing)
School of Emergency Management and Safety Engineering, North China University of Science and Technology

我国深部(以下均指埋深大于2 000 m)煤层气资源丰富，勘探开发潜力巨大。与中浅部相比，深部煤层气在富集成藏规律与开发方式方面均具有显著的差异性，急需针对重点区块开展解剖性分析研究。神木–佳县区块位于鄂尔多斯盆地东北部，目前尚处于深部煤层气勘探的起步阶段，深部煤层气富集特征及开发潜力等尚不明确。基于研究区近期实施的地震资料、300余口井的测井资料和4口取心井的参数资料等，系统分析煤储层基础地质特征，总结煤层气富集主控因素与富集规律，类比剖析研究区深部煤层气勘探开发潜力。研究区深8号煤的镜质体反射率介于0.7%~1.8%，大部分区域煤层演化已处于热解生气高峰，区域上煤层净煤厚度高达7~8 m，煤层发育稳定，构造相对简单、水动力封闭性较强、顶底板封盖条件较好，为煤层气大面积连续成藏提供了优越条件，其中佳县南区的煤层气资源条件最好。与鄂尔多斯盆地东部其他区块深部煤层相比，研究区煤层中游离气占比明显更高(15.21%~46.47%)，煤层中吸附气主要受吸附压力封存控制，而游离气受毛管力封闭与浮力重力分异双重控制，两种封存机制共同决定了深部煤层含气量的垂向分带与平面分区，以佳县南部为例总结了吸附气吸附压力主控、游离气毛管压力封闭与重力分异耦合控制的典型深部煤层气富集模式。与临兴区块和大宁–吉县区块类比分析结果表明，神木–佳县区块具有较好的煤层气资源基础、储层改造条件和高产潜力，预示了此区块深部煤层气规模化开发的美好前景。此外，大宁–吉县区块深部属典型的高煤阶煤，而神木–佳县深部为中煤阶煤，因此，该研究认识进一步丰富完善了深部煤层气富集理论，对于全国深部煤层气勘探开发实践有重要指示意义。

China boasts abundant coalbed methane (CBM) resources in deep layers (burial depths: greater than 2000 m), with considerable potential for CBM exploration and development. Compared to medium and shallow CBM, deep CBM differs significantly in enrichment and accumulation patterns and exploitation means. Therefore, there is an urgent need to dissect key CBM blocks. The Shenmu-Jiaxian block, situated in the northeastern Ordos Basin, is currently in the early stages of deep CBM exploration, with enrichment characteristics and exploration potential remaining undefined. Based on recently obtained seismic data, logging data from over 300 wells, and analytical results from four cored wells, this study conducted a comprehensive analysis of the fundamental geological characteristics of coal reservoirs, identified the primary controlling factors and patterns for CBM enrichment, and analogically dissected the potential for deep CBM exploration in the study area. The No.8 deep coal exhibits vitrinite reflectance of 0.7%‒1.8%, indicating that the coalification in most parts of the study area is currently in the peak stage of pyrolytic gas generation. The No.8 deep coal seam exhibits regional net thicknesses of up to 7‒8 m, stable distribution, comparably simple structures, highly closed hydrodynamic conditions, and favorable roof and floor sealing conditions, which create favorable conditions for widespread, continuous CBM accumulation. Across the study area, the southern portion of Jiaxian County demonstrates the optimal CBM resource conditions. Compared to other deep blocks in the eastern Ordos Basin, the No.8 coal seam in the study area exhibits significantly higher proportions of free gas (15.21%‒46.47%). Moreover, its adsorbed gas is primarily governed by adsorption pressure-induced trapping, whereas its free gas is subjected to the dual controls of capillary pressure and buoyancy-gravity differentiation. Both trapping mechanisms jointly determine the vertical and planar zoning of gas content in the deep part of the coal seam. Taking the southern area of Jiaxian County as an example, this study summarized a typical deep CBM enrichment pattern, which consists of the predominant control of the adsorption pressure for adsorbed gas, followed by the control of the coupling of capillary pressure and buoyancy-gravity differentiation for free gas. The comparative analysis with the Linxing and Daning-Jixian blocks indicates that the Shenmu-Jiaxian block enjoys a solid resource foundation of CBM, favorable reservoir stimulation, and great potential for high production, hinting at a promising prospect for large-scale exploitation of deep CBM in this block. In addition, the deep part of the Daning-Jixian block is characterized by high-rank coals, while that of the Shenmu-Jiaxian block features medium-rank coals. Therefore, this study contributes to the enrichment and improvement of the theory about deep CBM enrichment, serving as indicators for the exploration and exploitation of deep CBM in China.

国家自然科学基金杰出青年基金项目(42125205)；国家自然科学基金重点基金项目(42130806)；中央高校基本科研业务费深时数字地球前沿科学中心“深时数字地球”中央高校科技领军人才团队项目(2652023001)

李国永，姚艳斌，王辉，等. 鄂尔多斯盆地神木–佳县区块深部煤层气地质特征及勘探开发潜力[J]. 煤田地质与勘探，2024，52(2)：70−80.

LI Guoyong，YAO Yanbin，WANG Hui，et al. Deep coalbed methane resources in the Shenmu-Jiaxian block, Ordos Basin, China: Geological characteristics and potential for exploration and exploitation[J]. Coal Geology & Exploration，2024，52(2)：70−80.