鄂尔多斯盆地深部本溪组煤孔隙特征及成因探讨以榆林M172井8煤为例  

Discussion on pore characteristics and forming mechanism of coal in the deep area,Ordos Basin:Case study of No.8 coal seam in Well M172 of Yulin area

作　　者：赵伟波 刘洪林 王怀厂[1] 刘德勋 李晓波 ZHAO Weibo;LIU Honglin;WANG Huaichang;LIU Dexun;LI Xiaobo(Exploration and Development Research Institute,PetroChina Changqing Oilfield Company,Xi'an 710018,China;Key Laboratory of Unconventional Oil and Gas of PetroChina,Beijing 100083,China;National Energy Shale Gas Research and Development(Experiment)Center,Langfang 065007,China;PetroChina Research Institute of Petroleum Exploration and Development,Beijing 100083,China)

机构地区：[1]中国石油长庆油田勘探开发研究院,陕西西安710018 [2]中国石油非常规油气重点实验室,北京100083 [3]国家能源页岩气研发(实验)中心,河北廊坊065007 [4]中国石油勘探开发研究院,北京100083

出　　处：《天然气地球科学》2024年第2期202-216,共15页Natural Gas Geoscience

基　　金：中国石油前瞻性基础性项目“煤层气新区新层系新领域战略与评价技术研究”(编号:2021DJ2303);中国石油攻关性应用性科技专项“深地煤岩气成藏理论与效益开发技术研究”(编号:2023ZZ18)联合资助。

摘　　要：寻找深部煤层气资源分布,亟待查明深部煤储层显微组分和孔隙分布特征。以M172井8#煤为例,开展鄂尔多斯盆地榆林地区煤岩显微组分、核磁共振孔隙和电镜成像,分析了榆林地区煤岩的孔裂隙类型、孔隙连通性、孔隙度和孔径结构分布等参数,探讨了孔隙结构与显微组分、煤气孔成因机制等影响煤层储集性能的主控因素。研究结果表明:①饱和水煤样核磁弛豫时间T2发育3个峰,峰值位于0.2ms、8ms和300ms处,分别对应吸附孔、过渡孔和游离孔,并以吸附孔为主。煤样总孔隙度、有效孔隙度都随着镜质组分的含量增加而增大;煤岩中气孔与液态烃产生有关,基质镜质体发育液态烃裂解产生的气孔群。③深层煤层存在游离气与吸附气2种赋存状态,煤层含气量更高,含气饱和度普遍超饱和,煤层气成藏主控因素更为复杂,发育断层遮挡、水动力圈闭、构造-岩性和微幅构造等多种成藏类型,成藏类型比中浅层更加丰富。通过对深部煤岩孔隙结构特征的研究与成因分析对于明确深部煤层气成藏规律具有一定地质意义。To search for the distribution of deep coalbed methane resources,it is urgent to identify the macerals and pore distribution characteristics of deep coal reservoirs.Therefore,taking the No.8 coal seam in Well M172 as an example,the paper conducted coal macerals,nuclear magnetic resonance porosity,and electron microsco⁃py imaging in the Yulin area.The paper analyzed the parameters such as pore fracture types,pore connectivity,porosity,and pore structure distribution of coal rocks in the Yulin area,and explored the main controlling fac⁃tors that affect coal seam reservoir performance,such as pore structure and macerals,as well as the mechanism of gas pore formation.The research results indicate that:(1)There are three peaks in the nuclear magnetic re⁃laxation time T2 of saturated water coal samples,with peaks located at 0.2 ms,8 ms,and 300 ms,correspond⁃ing to adsorption pores,transition pores,and free pores,respectively,with adsorption pores being the main ones.(2)The total porosity and effective porosity of coal samples increase with the increase of vitrinite content;pores in coal rocks are related to the production of liquid hydrocarbons,and the matrix vitrinite develops a group of pores generated by the cracking of liquid hydrocarbons.(3)There are two types of occurrence states in deep coal seams:free gas and adsorbed gas.The coal seam has a higher gas content,and the gas saturation is general⁃ly supersaturated.The main controlling factors for coalbed methane accumulation are more complex,with multi⁃ple types of reservoir formation developed,such as fault shielding,hydrodynamic traps,structural lithology,and micro structures.The types of reservoir formation are more abundant than those in the middle and shallow layers.The study and genetic analysis of the pore structure characteristics of deep coal and rock in this article have certain geological significance for clarifying the formation laws of deep coalbed methane reservoirs.

关 键 词：深部煤层气 气孔 气泡变孔效应 核磁共振技术 鄂尔多斯盆地 

分 类 号：TE122.2[石油与天然气工程—油气勘探]