我国深部煤层气资源丰富且开发潜力巨大,实现规模开发有助于形成煤系气大产业,服务 油气增储上产,保障国家能源安全。 在系统总结近年深部煤层气勘探开发成果基础上,结合实验测 试和理论分析,揭示了深部差异含气系统模式,并针对性提出了开发策略。 研究结果表明,受构造 演化和保存条件差异影响,煤层气存在过饱和干煤系统、饱和 ~ 近饱和湿煤系统和欠饱和湿煤系 统。 干煤系统游离气含量高,且在深煤层中呈压缩状态,在储层压力>10 MPa 条件游离气含量可以 达到并超过吸附气,易形成高产。 湿煤系统中煤岩裂隙或者大孔隙中饱和地层水,需要排水降压解 吸产气。 煤层在煤化作用过程中生烃超压,纳米孔隙中饱和游离气且地层水难以侵入。 深部吸附 气和游离气处于动态转化,受范德华力、毛细管力和浮力作用综合影响,深煤层形成连续型天然气 藏,具有“ 源岩控储” ( 连续稳定煤层控制储层质量) 和“ 物性控藏” ( 物性差异影响甜点分布) 特征, 可在封盖条件良好的稳定高渗煤层寻找甜点区。 深煤层压实致密且地应力高,煤岩抗压强度增加, 储层改造裂缝有序性增强,可在不同粒径支撑剂下形成立体渗流网络。 干煤系统改造以体积改造 和“碎裂化”为主要目的,考虑采用水平井大规模分段压裂,扩大渗流面积,提高产气速度;湿煤系 统以适度改造和“疏导化”为主要方式,并考虑水平井顶板间接压裂等开发策略。 煤成气在地质历 史中持续向邻近层系充注运聚,形成全含气系统,应当充分利用成熟探区地质和工程基础,整体部 署,分类突破,多气合采,实现深部煤层气规模化开发和多类型天然气总体动用。

The realization of large-scale development of deep coalbed methane (CBM),which is abundant and has huge development potential in China,is beneficial to establish a large coal measure gas industry,serving the incre- ment of oil and gas reserves and ensuring national energy security. Based on the systematic summary of the exploration and development achievements of deep CBM in recent years,the differences of deep CBM bearing system models and corresponding development strategies are revealed by the combination of experiments and theoretical analysis. The results show that the deep CBM can be divided into over-saturated dry coal system,saturated to near-saturated wet coal system and under-saturated wet coal system due to different tectonic evolution and preservation conditions. In the dry coal system,when the reservoir pressure is higher than 10 MPa,the free gas can be compressed in the coals and exceeds the maximum content of adsorbed gas, which is easy to have a high production. The fractures or some macropores in the wet coal system are saturated by water,which needs the process of drainage,depressurization and desorption to produce gas. In the process of continuous hydrocarbon generation in coals,a large amount of free gas is generated from nanopores to form overpressure,which inhibits the formation water invasion. The adsorbed gas and free gas in the deep coals are in dynamic transformation. However, under the comprehensive influence of Van der Waals force,capillary force and buoyancy,the coals can form continuous - quasi continuous natural gas reservoirs, showing the characteristics of “source rock controlled reservoir” (continuous and stable coal seams influence reservoir quality) and “physical property control reservoir” (physical property affects sweet spots distribution),and thus the sweet spots can be found in stable high permeability coal seams with good sealing conditions. The deep coals are com- pacted densely with high in-situ stresses,which leads to the increment of compressive strength of coals and enhance- ment ordering of reservoir reconstruction fractures. Thus,the three-dimensional seepage network can be formed by dif- ferent particle size proppants. For the successful production of dry coal system,a large-scale staged fracturing of hori- zontal wells can be adopted to expand the flow area,improve the gas production rate,and achieve the main purpose of volume fracturing and “fragmentation”. However,the wet coal system mainly adopts moderate transformation and “dredging”,and considers strategies such as an indirect fracturing of horizontal well roof. During the geological history,coal derived methane continues to migrate and accumulate in adjacent strata,forming a full gas bearing system. In the mature exploration areas,the basic geology and engineering understanding should be fully evaluated,making strategies for “overall deployment” and “categorized breakthrough”,to achieve a large-scale development of deep CBM and an overall recovery of multiple natural gases.