鄂尔多斯盆地东北部斜坡区深层煤层气地质特征与勘探潜力

Geological characteristics and exploration potential of deep coalbed methane in the slope area of the northeastern Ordos Basin

赵石虎 刘曾勤 申宝剑 罗兵 陈刚 陈新军 张嘉琪 万俊雨 刘子驿 刘友祥

Shihu ZHAO Zengqin LIU Baojian SHEN Bing LUO Gang CHEN Xinjun CHEN Jiaqi ZHANG Junyu WAN Ziyi LIU Youxiang LIU

近年来，鄂尔多斯盆地北部大牛地地区深层煤层气勘探取得重大突破。利用区域地质资料、岩心观察、显微组分分析、扫描电镜、工业分析、压汞测试、低温液氮吸附、二氧化碳吸附、甲烷等温吸附以及现场含量测试等多种技术多段，研究大牛地地区深部煤层的空间展布、煤岩煤质、储集性和含气性等地质特征，以明确该区深层煤层气勘探潜力。结果表明，大牛地地区主力煤储层太原组8煤层：①全区稳定分布，厚度2 ~ 14 m，镜质体反射率（）1.7 %，上部层段发育光亮-半亮煤，灰分较低，煤质条件较好，具备煤层气富集的物质基础。②微孔和宏孔都较发育，以微孔为主，占比为67.5 %，低灰光亮-半亮煤的总孔容、孔隙比表面积、微孔占比及孔隙度较大。③顶板发育厚层灰岩与暗色泥岩，构造简单，地层含水量低，属于干煤含气系统，总含气量20.3 ~ 47.1 m/t，游离气占比33.2 % ~ 66.2 %，煤储层具有吸附气-游离气双富特征。④含气面积2 003 km，资源量5 422×10 m，资源丰度2.71×10 m/km。鄂尔多斯盆地北部深部煤层具有有利煤层气地质特征，是重要的勘探开发目的层。

In recent years， significant breakthroughs have been achieved in the exploration of deep coalbed methane （CBM） in the Daniudi area， northern Ordos Basin. This study aims to determine the potential for deep CBM exploration in this area. Based on regional geology and data derived from core and maceral observations， scanning electron microscopy （SEM） image analysis， proximate analysis， mercury injection capillary pressure （MICP） analysis， low-temperature liquid-nitrogen adsorption measurements， and CO adsorption and methane isothermal adsorption experiments， along with on-site gas content tests， we delve into the geological characteristics of deep coal seams in the Daniudi area in terms of their spatial distribution， lithotypes， coal quality， reservoir properties， and gas-bearing properties. The No. 8 coal seam of the Taiyuan Formation is identified as the dominant coal reservoir in the Daniudi area. The results indicate that this coal seam is consistently distributed throughout the Daniudi area， with a thickness ranging from 2 to 14 m and vitrinite reflectance （） of 1.7 %. Bright to semi-bright coals occur in the upper part of the coal seam as featuring low ash content， indicating high coal quality and providing a material basis for CBM accumulation. The No. 8 coal seam shows well-developed micropores and macropores， with micropores being predominant， accounting for 67.5 %. The bright to semi-bright coals with low ash content therein display high total pore volume， specific surface area of pores， micropore proportion， and porosity. The roof of the coal seam contains thickly laminated limestones and dark mudstones， as characterized by simple structure and low formation water content， suggesting a dry-coal gas-bearing system. With total gas content ranging from 20.3 to 47.1 m/t and free gas proportion from 33.2 % to 66.2 %， the No. 8 coal seam is rich in both adsorbed and free gases. This coal seam manifests a gas-bearing area of 2 003 km， CBM resources of 5 422 × 10 m， and CBM resource abundance of 2.71 × 10 m/km. These findings indicate that deep coals in the Ordos Basin are characterized by favorable geological condition for CBM generation， representing a significant exploration and development target.

10.11743/ogg20240610