Unique connotation of geological-engineering dual sweet spot evaluation for effective coalbed methane exploitation

Authors

• LUO Pingya, State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610599, ChinaFollow
• ZHU Suyang, State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610599, ChinaFollow

Abstract

Objective In China, the exploitation of deep and shallow coalbed methane (CBM) still relies on the evaluation approach oriented to the geological-engineering dual sweet spots of unconventional hydrocarbons. However, exemplary CBM production technologies delivered unsatisfactory performance in other blocks and failed to find wide application even in zones with overlapping geological and engineering sweet spots. This issue represents the principal theoretical and technical challenge confronting the comprehensive development of the CBM industry in China. Methods This study aims to elucidate the causes of this issue and provide corresponding solutions, as well as clarifying the conditions for the effective linkage between geological and engineering sweet spots. Based on the unique chain-like CBM mass transfer pattern consisting of desorption from pore walls, diffusion in matrix, seepage into cleats, and flow in fractures with high hydraulic conductivity, this study explored the coupling relationship between the fluid and solid mineral attributes of CBM reservoirs. Then, based on the CBM flow rate from matrix to cleats, this study analyzed the conditions for the linkage between geological and engineering sweet spots and revealed the unique connotation of geological-engineering dual sweet spot evaluation tailored to effective CBM exploitation. Results and Conclusions Different from other unconventional gas reservoirs, CBM reservoirs are characterized by distinct solid and fluid mineral attributes. The recoverability assessment of fluid mineral resources necessitates the assessment of reservoir physical properties, while the reserve recoverability of solid mineral resources should involve the physical properties of surrounding rocks. In the case where the CBM flow rate from matrix to cleats is inherently high or can be significantly enhanced using engineering measures, the fluid mineral attribute of CBM predominates. In this case, the high production of CBM wells can be achieved only when geological and engineering sweet spots overlap in space. Therefore, in addition to existing parameters for geological-engineering dual sweet spot evaluation, the recoverability evaluation of CBM reservoirs should highlight the CBM flow rate from matrix to cleats. To investigate the geological sweet spots of CBM, the saturation and abundance indices of free gas in cleats should be supplemented. For the engineering sweet spot evaluation of CBM, greater emphasis should be placed on the coupling effect between coal seams and surrounding rocks’ physical properties in the solid mineral attribute of CBM.

Keywords

coalbed methane (CBM), chain-like mass transfer, geological sweet spot, engineering sweet spot, CBM mobility in matrix, fluid mineral attribute, solid mineral attribute

DOI

10.12363/issn.1001-1986.26.02.0073

Recommended Citation

L Z. (2026) "Unique connotation of geological-engineering dual sweet spot evaluation for effective coalbed methane exploitation," Coal Geology & Exploration: Vol. 54: Iss. 9, Article 2.
DOI: 10.12363/issn.1001-1986.26.02.0073
Available at: https://cge.researchcommons.org/journal/vol54/iss9/2

Reference

[1] 邹才能,林敏捷,马锋,等. 碳中和目标下中国天然气工业进展、挑战及对策[J]. 石油勘探与开发,2024,51(2):418−435. ZOU Caineng,LIN Minjie,MA Feng,et al. Development,challenges and strategies of natural gas industry under carbon neutral target in China[J]. Petroleum Exploration and Development,2024,51(2):418−435.

[2] 贾爱林,程刚,陈玮岩,等. 双碳背景下中国天然气供需形势预测[J]. 石油勘探与开发,2023,50(2):431−440. JIA Ailin,CHENG Gang,CHEN Weiyan,et al. Forecast of natural gas supply and demand in China under the background of "Dual Carbon Targets"[J]. Petroleum Exploration and Development,2023,50(2):431−440.

[3] 徐凤银,侯伟,熊先钺,等. 中国煤层气产业现状与发展战略[J]. 石油勘探与开发,2023,50(4):669−682. XU Fengyin,HOU Wei,XIONG Xianyue,et al. The status and development strategy of coalbed methane industry in China[J]. Petroleum Exploration and Development,2023,50(4):669−682.

[4] 李国欣,张水昌,何海清,等. 煤岩气:概念、内涵与分类标准[J]. 石油勘探与开发,2024,51(4):783−795. LI Guoxin,ZHANG Shuichang,HE Haiqing,et al. Coal–rock gas:Concept,connotation and classification criteria[J]. Petroleum Exploration and Development,2024,51(4):783−795.

[5] 秦勇,申建,史锐. 中国煤系气大产业建设战略价值与战略选择[J]. 煤炭学报,2022,47(1):371−387. QIN Yong,SHEN Jian,SHI Rui. Strategic value and choice on construction of large CMG industry in China[J]. Journal of China Coal Society,2022,47(1):371−387.

[6] 罗平亚,朱苏阳. 中国建立千亿立方米级煤层气大产业的理论与技术基础[J]. 石油学报,2023,44(11):1755−1763. LUO Pingya,ZHU Suyang. Theoretical and technical fundamentals of a 100 billion–cubic–meter–scale large industry of coalbed methane in China[J]. Acta Petrolei Sinica,2023,44(11):1755−1763.

[7] 赵喆,徐旺林,赵振宇,等. 鄂尔多斯盆地石炭系本溪组煤岩气地质特征与勘探突破[J]. 石油勘探与开发,2024,51(2):234−247. ZHAO Zhe,XU Wanglin,ZHAO Zhenyu,et al. Geological characteristics and exploration breakthroughs of coal rock gas in Carboniferous Benxi Formation,Ordos Basin,NW China[J]. Petroleum Exploration and Development,2024,51(2):234−247.

[8] 杨帆,李斌,王昆剑,等. 深部煤层气水平井大规模极限体积压裂技术:以鄂尔多斯盆地东缘临兴区块为例[J]. 石油勘探与开发,2024,51(2):389−398. YANG Fan,LI Bin,WANG Kunjian,et al. Extreme massive hydraulic fracturing in deep coalbed methane horizontal wells:A case study of the Linxing Block,eastern Ordos Basin,NW China[J]. Petroleum Exploration and Development,2024,51(2):389−398.

[9] 陈新军,刘曾勤,申宝剑,等. 深层煤层气勘探开发标准体系的战略布局与优化路径[J]. 煤田地质与勘探,2026,54(4):50−60. CHEN Xinjun,LIU Zengqin,SHEN Baojian,et al. Strategic layout and optimization paths of the standard system for the exploration and exploitation of deep coalbed methane[J]. Coal Geology & Exploration,2026,54(4):50−60.

[10] 许浩,汤达祯,陶树,等. 深、浅部煤层气地质条件差异性及其形成机制[J]. 煤田地质与勘探,2024,52(2):33−39. XU Hao,TANG Dazhen,TAO Shu,et al. Differences in geological conditions of deep and shallow coalbed methane and their formation mechanisms[J]. Coal Geology & Exploration,2024,52(2):33−39.

[11] 罗平亚. 关于大幅度提高我国煤层气井单井产量的探讨[J]. 天然气工业,2013,33(6):1−6. LUO Pingya. A discussion on how to significantly improve the single–well productivity of CBM gas wells in China[J]. Natural Gas Industry,2013,33(6):1−6.

[12] 李勇,徐立富,刘宇,等. 深部煤层气水赋存机制、环境及动态演化[J]. 煤田地质与勘探,2024,52(2):40−51. LI Yong,XU Lifu,LIU Yu,et al. Occurrence mechanism,environment and dynamic evolution of gas and water in deep coal seams[J]. Coal Geology & Exploration,2024,52(2):40−51.

[13] 张学英,王钧剑,王刚,等. 煤层气藏气体产出路径研究:以沁水盆地南部马必东区块为例[J]. 油气地质与采收率,2020,27(2):137−142. ZHANG Xueying,WANG Junjian,WANG Gang,et al. Gas production path of coalbed methane reservoir:A case study of Mabidong Block,southern Qinshui Basin[J]. Petroleum Geology and Recovery Efficiency,2020,27(2):137−142.

[14] 卢义玉. 建井开采过程中甲烷解吸、扩散、渗流过程及其运移规律研究[R]. 中国工程院2025年重大咨询项目《我国建成千亿方级煤层气大产业发展战略路径研究》审查会，2025年12月21日.

[15] ZHU Suyang,SALMACHI A,DU Z. Two phase rate–transient analysis of a hydraulically fractured coal seam gas well:A case study from the Ordos Basin,China[J]. International Journal of Coal Geology,2018,195:47−60.

[16] SALMACHI A,CLARKSON C,ZHU Suyang,et al. Relative permeability curve shapes in coalbed methane reservoirs[C]//SPE Asia Pacific Oil and Gas Conference and Exhibition. Brisbane:Society of Petroleum Engineers,2018:SPE–192029–MS.

[17] CLARKSON C R. Unconventional reservoir rate–transient analysis[M]. Oxford:Elsevier,2021.

[18] 朱苏阳,向东流,彭小龙,等. 一种煤层气可采性的矿场快速评价方法:CN117759236B[P]. 2025-05-23.

[19] 姚艳斌,王辉,杨延辉,等. 煤层气储层可改造性评价:以郑庄区块为例[J]. 煤田地质与勘探,2021,49(1):119−129. YAO Yanbin,WANG Hui,YANG Yanhui,et al. Evaluation of the hydro–fracturing potential for coalbed methane reservoir:A case study of Zhengzhuang CBM field[J]. Coal Geology & Exploration,2021,49(1):119−129.

[20] 张兵,李勇,贾雨婷,等. 薄–超薄煤层特征及天然气合层开发突破:以沁水盆地潘河区块为例[J]. 天然气工业,2023,43(10):83−93. ZHANG Bing,LI Yong,JIA Yuting,et al. Characteristics and commingled natural gas production breakthrough of thin and ultra–thin coal beds in the Panhe Block of the Qinshui Basin[J]. Natural Gas Industry,2023,43(10):83−93.

[21] 张万春,郭布民,孔鹏,等. 柿庄南煤层气重复压裂裂缝形态反演及效果分析评价[J]. 非常规油气,2022,9(1):119−128. ZHANG Wanchun,GUO Bumin,KONG Peng,et al. Fracture morphology inversion and effect evaluation of CBM refracturing in southern Shizhuang Block[J]. Unconventional Oil & Gas,2022,9(1):119−128.

[22] 许耀波,朱玉双,张培河. 沁水盆地赵庄井田煤层气产出特征及其影响因素[J]. 天然气地球科学,2019,30(1):119−125. XU Yaobo,ZHU Yushuang,ZHANG Peihe. The characteristics of coalbed methane production and its affecting factors in Zhaozhuang field,Qinshui Basin[J]. Natural Gas Geoscience,2019,30(1):119−125.

[23] 尹帅,丁文龙,高敏东,等. 樊庄北部3号煤层现今应力场分布数值模拟[J]. 西南石油大学学报(自然科学版),2017,39(4):81−89. YIN Shuai,DING Wenlong,GAO Mindong,et al. The in-situ stress field distribution numerical simulation of No. 3 coal seam in the north of Fanzhuang CBM well blocks[J]. Journal of Southwest Petroleum University (Science & Technology Edition),2017,39(4):81−89.

[24] 叶建平,吴建光,房超,等. 沁南潘河煤层气田区域地质特征与煤储层特征及其对产能的影响[J]. 天然气工业,2011,31(5):16−20. YE Jianping,WU Jianguang,FANG Chao,et al. Regional geological and reservoir characteristics of the Panhe CBM gas field in the southern Qinshui Basin and their influences on CBM gas production capacity[J]. Natural Gas Industry,2011,31(5):16−20.

[25] 安琦,杨帆,杨睿月,等. 鄂尔多斯盆地神府区块深部煤层气体积压裂实践与认识[J]. 煤炭学报,2024,49(5):2376−2393. AN Qi,YANG Fan,YANG Ruiyue,et al. Practice and understanding of deep coalbed methane massive hydraulic fracturing in Shenfu Block,Ordos Basin[J]. Journal of China Coal Society,2024,49(5):2376−2393.

[26] 刘晓. 不同压裂规模下煤储层缝网形态对比研究:以延川南煤层气田为例[J]. 油气藏评价与开发,2024,14(3):510−518. LIU Xiao. Comparison of seam network morphology in coal reservoirs under different fracturing scales:A case of Yanchuannan CBM gas field[J]. Petroleum Reservoir Evaluation and Development,2024,14(3):510−518.

[27] 吴群. 延川南煤储层地应力条件及其对煤层气产能的影响[D]. 西安:西北大学,2012. WU Qun. Study on in-situ stress condition of coal reservoir and effects on CBM well production in Yanchuannan Block,Ordos Basin[D]. Xi'an:Northwest University,2012.

[28] 王小华. 韩城区块浅层煤层煤岩类型制约下的水力裂缝扩展规律研究[D]. 北京:中国石油大学(北京),2019. WANG Xiaohua. Investigation on the propagation of hydraulic fracture under the influence of coal macrolithotypes in shallow coal seam of Hancheng Block[D]. Beijing:China University of Petroleum (Beijing),2019.

[29] 高杰. 含煤系产层组压裂裂缝穿层扩展机制研究[D]. 北京:中国石油大学(北京),2018. GAO Jie. Propagation mechanism of through strata fractured cracks in multi–layered reservoir[D]. Beijing:China University of Petroleum (Beijing),2018.

[30] 黄赛鹏. 沁南郑庄区块煤储层地应力特征与压裂裂缝扩展机制研究[D]. 北京:中国地质大学(北京),2017. HUANG Saipeng. Study on the in-situ stress characteristics of coal reservoir and hydraulic fracture propagation mechanism in Zhengzhuang field,Qinshui Basin,China[D]. Beijing:China University of Geosciences (Beijing),2017.

[31] 吴百烈. 煤层气井水力压裂几何参数优化设计[D]. 北京:中国石油大学(北京),2011. WU Bailie. Geometry parameter designing of hydraulic fracturing in coalbed methane wells[D]. Beijing:China University of Petroleum (Beijing),2011.

[32] 刘度. 复杂煤体结构煤储层水力压裂裂缝起裂及扩展机制研究[D]. 北京:中国矿业大学(北京),2021. LIU Du. Study on the crack initiation and propagation mechanism of hydraulic fracturing with complex coal structure in coal reservoir[D]. Beijing:China University of Mining and Technology (Beijing),2021.

[33] 梁萧磊. 滇东老厂地区多煤层水力压裂数值模拟研究[D]. 北京:中国地质大学(北京),2021. LIANG Xiaolei. Numerical simulation of hydraulic fracturing of multiple coal seams in Laochang area of eastern Yunnan[D]. Beijing:China University of Geosciences (Beijing),2021.

[34] 王博. 老厂雨旺区块煤储层特征及水力压裂优化设计[D]. 徐州:中国矿业大学,2018. WANG Bo. Coal reservoir characteristics and hydraulic fracturing optimization design of Yuwang Block in Laochang[D]. Xuzhou:China University of Mining and Technology,2018.

[35] 朱苏阳,刘伟,彭小龙,等. 一种基于围岩聚焦效应的深层煤层气可采性评价方法:CN118378840B[P]. 2025-03-28.