Theoretical and technological difficulties and countermeasures of deep CBM exploration and development in the eastern edge of Ordos Basin
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摘要: 我国深部(层)(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。2019年以来，鄂尔多斯盆地东缘(鄂东缘)大宁–吉县区块逐步进入深部(层)煤层气“规模勘探+先导试验”阶段，直井日产气量突破2×104 m3，水平井日产气量突破10×104 m3，这一标志性成果既突破传统意义上煤层气勘探开发领域的深度禁区，使得煤层气总资源量有望在30.05×1012 m3基础上大幅度增加，又将成为“十四五”乃至长远煤层气产业实现规模发展的重点勘探开发方向。面对以地面传统钻井、压裂(储层改造)、排采(举升)、集输和数智化等为主体技术及开发方式的迫切需求，鄂东缘深部(层)煤层气面临许多基础理论和技术难点，包括：成藏机理和赋存规律，有利区优选方法；高产主控因素及控制机理，解吸–渗流机理与开发规律，“地质–工程一体化”开发甜点分类评价标准，关键开发指标确定方法和依据；低成本优快高效钻完井技术，水平井水泥环高效密封控制技术；煤岩缝网形成机理，低成本、高效、环保压裂入井材料，改造后缝网孔渗特征、流动规律；高盐、高水气比、出砂等工况下排采及举升控制技术；高效节能集输、规模开发所需复杂集输管网稳定运行理论与实践体系；数智气田建设和人工智能应用研究。在系统梳理上述难点基础上，针对性地提出勘探地质、开发地质、钻完井、压裂(储层改造)、排采(举升)、集输与数智化等理论与技术的研究方向和具体对策，这一成果不仅对加快鄂东缘深部(层)煤层气规模上产具有重要的指导意义，而且对国内外深部(层)煤层气规模开发具有很强的引领和示范作用，也可有力推动煤层气产业高质量发展、支撑实现国家碳达峰碳中和目标与保障清洁能源安全。Abstract: Deep coalbed methane (CBM) resources (hereinafter referred to the CBM resources with the buried depth greater than 2 000 m) are abundant in China and have great potential in exploration and development. Since 2019, Daning‒Jixian block in the eastern edge of Ordos Basin has entered the stage of "scaled exploration + pilot test" of deep CBM, with the daily gas production exceeding 2 × 104 m3 in vertical wells and 10 × 104 m3 in horizontal wells. This remarkable achievement has broken through the traditional depth limitation in CBM exploration and development. Thus, the total resource of CBM is expected to increase significantly on the basis of 30.05 × 1012 m3, and the deep CBM resource will become a key direction of exploration and development for the scaled development of CBM industry in the "fourteenth five year plan" and even in long term. In view of the urgent needs of development mode with traditional surface drilling, fracturing (reservoir stimulation), drainage and production (lifting), gathering and digital intelligence as the main technologies, many basic theoretical and technical difficulties are faced in the development of the deep CBM in the eastern edge of Ordos Basin: the optimization method of favorable areas based on accumulation mechanism and occurrence state, the main control factors and control mechanism of high yield, the desorption-seepage mechanism and development law, the evaluation standard of development dessert with “geology-engineering integration”, and the determination method and basis of key development indicators, the low-cost, fast and efficient drilling and completion technology, the efficient cement sheath sealing control technology for horizontal wells, the formation mechanism of deep coal rock fracture network, the low-cost, efficient and environmentally friendly fracturing materials, the porous and permeable characteristics and flow law of fracture network after fracturing, the drainage and lifting control technology under the working conditions of high salinity, high water-gas ratio and sand production, the theory and practice system for stable operation of complex gathering pipeline network required for the efficient and energy-saving gathering and the scaled development, the digital and intelligent construction of gas field, and the application research of artificial intelligence. On the basis of systematically sorting out the above difficulties, the research direction and specific countermeasures were put forward for the theory and technology on exploration geology, development geology, well drilling and completion, fracturing (reservoir stimulation), drainage production (lifting), gathering and digital intelligence. This achievement not only has important guiding significance for accelerating the scaled production of deep CBM in the eastern edge of Ordos Basin, but also has a strong leading and demonstration role for the scaled development of deep CBM at home and abroad. In addition, it could also effectively promote the high-quality development of CBM industry, and support the realization of the national goal of "carbon peaking and carbon neutrality", so as to ensure the security of clean energy.
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图 1 区域构造纲要及大宁−吉县区块位置
Fig. 1 Outline of regional structure and location of Daning‒Jixian block
图 2 大宁–吉县区块深部(层)煤层气典型井排采曲线
Fig. 2 Drainage production curve of typical wells for deep CBM in Daning‒Jixian block
图 3 深部(层)煤层气勘探开发全息大数据分析与数智化平台框架
Fig. 3 Holographic big data analysis and digital intelligence platform for deep CBM exploration and development
图 4 鄂东缘深部(层)煤层气成藏理论及高效开发技术研究对策技术路线
Fig. 4 Countermeasure and technical route for research on accumulation theory and efficient development technology of deep CBM in the eastern margin of Ordos Basin
图 5 深部(层)煤层气成藏理论与勘探有利区优选技术路线
Fig. 5 Accumulation theory and technical route for optimization of favorable area of exploration of deep CBM
图 6 深部(层)煤层气开发甜点分类评价及技术政策优化研究技术路线
Fig. 6 Technical route for evaluation of deep CBM development dessert and research on technical policy of development
图 7 深部(层)煤层气水平井大规模压裂(储层改造)关键技术研究技术路线
Fig. 7 Technical route for research on key technology of scaled fracturing (reservoir stimulation) of deep CBM horizontal wells
表 1 大宁−吉县区块深部(层)与中深部(层)8号煤层地质−气藏特征对比[4]
Table 1 Comparison of geological and gas reservoir characteristics of deep and middle-deep No.8 coal seam in Daning‒Jixian block[4]
地质气藏条件 中深部(层)8号煤层 深部(层)8号煤层 深部(层)煤层特征 深部(层)相比中深
部(层)的定量关系埋深/m 1 000~1 500 2 000~2 520 埋深更深 煤层厚度/m 平均5.49 平均7.8 厚度相对更大 含气量/(m3·t−1) 6.14~20.84，平均12.36 18~26，平均25.2 含气量更高 2倍 孔隙率/% 平均3.98 平均3.13 均属特低孔隙率 渗透率/10−3 μm2 0.005~3.01/1.51(注入/压降试井) 0.053~0.054/0.0535(注入/
压降试井)渗透率更低，属特低渗透率
储层低2个数量级 割理/裂缝 面割理16~18条/5 cm；
端割理
12条/5 cm，
呈网状面割理6~10条/5 cm；
端割理7~15条/5 cm，
割理呈线状、网状面割理相对较少，端割理相当 含气饱和度/% 49.6~86.2/69.5 97.99~100/98.95 含气饱和度更高 1.4倍 甲烷体积分数/% 92.82~98.64/96.48 94.81~96.65/95.43 甲烷占比相当 等温吸附特征 VL平均24.9 m3/t，pL平均2.09 MPa VL平均28.29 m3/t，
pL平均3.06 MPaVL、pL，吸附能力强 宏观煤岩类型 半亮煤、半暗煤为主 光亮煤、半亮煤为主 光亮煤、半亮煤为主 煤体结构 碎裂、碎粒煤为主 原生结构煤为主 原生结构煤为主 煤岩显微组分 镜质组为主，体积分数60% 镜质组为主，
体积分数85.5%镜质组含量更高 1.4倍 镜质体平均反射率/% 2.2 2.7 相对较高 1.2倍 煤储层压力/MPa 7.64~7.66 17.02~20.74 煤储层压力更高 2.6倍 地层压力系数 0.61~0.94 0.902~0.936 系数相对更高 煤储层温度/℃ 30.50~51.19 61.3~73.4 温度更高 1.5倍 顶底板特征 顶板以灰岩为主，
底板以泥岩为主，含水性弱顶板以灰岩为主，底板以
泥岩为主，含水性弱相当 水文地质条件 承压区–弱径流区 承压区 水动力条件更弱 地层水特征 水型为CaCl2–NaHCO3型，
矿化度4 300~12 700 mg/L水型CaCl2型，矿化度
40 158~332 006 mg/L矿化度更高 20倍 甲烷碳同位素
δ13CPDB/‰−38.8 −20.9 相对更高 
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表 2 吉深6-7平01井水质分析结果
Table 2 Analysis results on quality of produced water from JS6-7P01
检测项目 结果/(mg·L−1) 检测项目 结果/(mg·L−1) K+ 572.00 Cl− 35 500 Na+ 35 400.00 SO4 2− 11.42 Ca2+ 16 050.00 NO2 − 4.29 Mg2+ 5 100.00 NO3 − 26.55 Fe3+ 2.04 PO4 3− 2.09 Al3+ − HCO3 − 579.50 NH4 + 1 770.12 CO3 2− 0 阳离子总值 58 894.16 阴离子总值 36 123.85 总硬度 21 150.00 总矿化度 223 913.00 总碱度 475.50 游离CO2 192.20 COD(化学需氧量) 20 000.00 侵蚀CO2 0 可溶性SiO2 300.70
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表 3 大宁−吉县区块深部(层)煤层气水平井钻完钻情况
Table 3 Drilling and completion of deep CBM horizontal wells in Daning‒Jixian block
井号 水平段/
m钻遇率/
%钻井周期/d 完井周期/d 完钻井深/m 大吉−平25-3H 902 93.10 99.29 112.69 3 422 吉深−平01 1 270 61.47 85.79 96.87 3 812 吉深−平02 1 285 74.20 54.21 74.88 3 745 吉深6-7平01 1 000 94.80 30.83 34.40 3 601
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