深部煤岩地质特征及煤层气富集主控地质因素——以鄂尔多斯盆地东部M区为例

Geological characteristics of deep coal rock and main geological factors controlling coalbed methane enrichment: a case study of the M area in the eastern Ordos Basin

郭晓娇 王雷 姚仙洲 李旭 张林科 王晓双

GUO Xiaojiao WANG Lei YAO Xianzhou LI Xu ZHANG Linke WANG Xiaoshuang

1. 西安石油大学 地球科学与工程学院, 西安 710065; 2. 西安石油大学 陕西省油气成藏地质学重点实验室, 西安 710065; 3. 中国石油集团东方地球物理勘探有限责任公司研究院 长庆分院, 西安 710021

1. School of Earth Sciences and Engineering, Xi'an Shiyou University, Xi'an, Shaanxi 710065, China; 2. Shaanxi Key Laboratory of Petroleum Accumulation Geology, Xi'an Shiyou University, Xi'an, Shaanxi 710065, China; 3. Changqing Branch, Geophysical Research Institute, BGP INC., CNPC, Xi'an, Shaanxi 710021, China

鄂尔多斯盆地M区上石炭统本溪组顶部8#厚煤层分布广泛，有机质热成熟度高。该区煤层埋深大、横向变化快、非均质性强，且煤岩基础地质特征及深部煤层气富集规律尚不明确、有利目标优选标准尚未建立，这严重制约了深部煤层气的高效勘探。为了促进深部煤层气的增储和高效产出，进一步发展鄂尔多斯盆地东部深部煤层气富集理论，基于研究区76口井的岩心观察、实验分析测试、扫描电镜、测—录井资料，结合三维地震资料，开展了深部煤层地质特征及煤层气富集主控因素两方面的研究工作，初步明确了该区深部煤层气的勘探潜力。鄂尔多斯盆地M区上石炭统本溪组顶部8#煤以焦煤—瘦煤为主，为中高阶煤；亮煤和半亮煤厚度为2～6 m；有机组分以镜质组为主，占比79.8%；工业组分表现为中高挥发分及灰分、固定碳丰富、低水分；煤岩储层孔缝发育，以原生孔隙为主，其孔隙主要由微孔和大孔组成；含气量介于16～25 m3/t之间。鄂尔多斯盆地东缘深部煤层气富集情况主要受煤储层、构造2个因素控制。以6 m以上的厚煤层发育区、远离断裂带(断距小于5 m)的裂缝发育区、微构造高点作为深部煤层气有利勘探区优选原则，优选出8#煤有利勘探面积共207 km2，其中Ⅰ类区97 km2，Ⅱ类区110 km2。

The 8# thick coal seam is widely distributed with high organic matter thermal maturity at the top of the Upper Carboniferous Benxi Formation in the M area of the Ordos Basin. However, the coal seams in this area are characterized by large burial depth, rapid lateral changes, strong heterogeneity, and unclear basic geological features and enrichment patterns of deep coalbed methane (CBM). The criteria for selecting favorable targets are yet to be established. These severely restrict the efficient exploration of deep CBM. To promote increased reserves and efficient production of deep CBM, and to further develop the enrichment theory of deep CBM in the eastern Ordos Basin, a comprehensive study was conducted based on core observations, experimental tests, scanning electron microscopy, well logging data from 76 wells in the study area, and 3D seismic data. The geological characteristics of deep coal seams and the main controlling factors of CBM enrichment were investigated, preliminary clarifying the exploration potential of this area. The results indicate that: The 8# coal seam at the top of the Upper Carboni-ferous Benxi Formation in the M area of the Ordos Basin is mainly composed of coking coal and lean coal, which are medium to high-ranked coals. The thickness of bright coal and semi-bright coal ranges from 2 to 6 m. Organic components are mainly vitrinite, accounting for 79.8%. Industrial components exhibit medium to high levels of volatile matter and ash, abundant fixed carbon, and low moisture content. The coal rock reservoir has well-developed pores and fractures, primarily composed of micropores and macropores. Gas content ranges between 16-25 m3/t. The enrichment of deep CBM in the eastern margin of the Ordos Basin is mainly controlled by coal reservoir and structural factors. Favorable exploration areas for deep CBM include regions with coal seams thicker than 6 m, areas with developed fractures far from fault zones (fault displacement less than 5 m), and microstructure high points. Based on these criteria, a favorable exploration area of 207 km2 for the 8# coal seam was identified, with 97 km2 classified as Type Ⅰ and 110 km2 as Type Ⅱ.

中国石油“十四五”前瞻性基础性重大科技项目(2021DJ2101)和西安石油大学硕士研究生创新与实践能力培养计划(YCS23113044)联合资助。

https://doi.org/10.11781/sysydz2025010017