鄂尔多斯盆地神木地区侏罗系延安组煤层微观孔隙结构特征  

Micro-pore structure characteristics of coal seams of Jurassic Yan’an Formation in Shenmu area,Ordos Basin

作　　者：李启晖 任大忠[1] 甯波[2] 孙振[3] 李天 万慈眩 杨甫 张世铭[5] LI Qihui;REN Dazhong;NING Bo;SUN Zhen;LI Tian;WAN Cixuan;YANG Fu;ZHANG Shiming(Engineering Research Center of Development and Management for Low to Ultra-Low Permeability Oil&Gas Reservoirs in West China,Ministry of Education,College of Petroleum Engineering,Xi’an Shiyou University,Xi’an 710065,China;PetroChina Research Institute of Petroleum Exploration&Development,Beijing 100083,China;No.6 Gas Production Plant,PetroChina Changqing Oilfield Company,Xi’an 710018,China;Key Laboratory of Coal Resources Exploration and Comprehensive Utilization,Ministry of Natural Resources,Xi’an 710021,China;PetroChina Research Institute of Petroleum Exploration and Development-Northwest,Lanzhou 730020,China)

机构地区：[1]西安石油大学石油工程学院/西部低渗-特低渗油藏开发与治理教育部工程研究中心,西安710065 [2]中国石油勘探开发研究院,北京100083 [3]中国石油长庆油田公司第六采气厂,西安710018 [4]自然资源部煤炭资源勘查与综合利用重点实验室,西安710021 [5]中国石油勘探开发研究院西北分院,兰州730020

出　　处：《岩性油气藏》2024年第2期76-88,共13页Lithologic Reservoirs

基　　金：陕西省重点研发计划基金“致密砂岩油藏微纳米孔喉内压裂液渗吸滞留的微观渗流机理研究”(编号:2021GY-140);西安石油大学研究生创新与实践能力培养项目“鄂尔多斯盆地神木地区侏罗系延安组煤层储层特征”(编号:YCS23113027);国家自然科学基金“水力压裂裂缝轨迹可控性理论基础-非均质地层裂缝控制理论基础研究”(编号:51934005)联合资助。

摘　　要：煤层孔隙结构对煤层气的吸附与扩散具有显著影响。通过气体吸附、核磁共振、扫描电镜等实验,对鄂尔多斯盆地神木地区侏罗系延安组煤岩开展煤层孔隙结构多尺度、多参数的联合表征研究,厘清了煤层气解吸—扩散—渗流的规律。研究结果表明:(1)神木地区延安组煤层平均孔隙度为6.89%,平均渗透率为4.82 mD,属典型的特低渗煤层,主要发育方解石、黏土矿物以及非晶质组分等,其中方解石平均质量分数为54.8%,黏土矿物平均质量分数为35.7%,非晶质平均质量分数为15.0%。(2)研究区煤层主要储集空间为狭缝形和墨水瓶形等,包括气孔、屑间孔、胞腔孔、铸模孔和少量微裂缝,孔隙以2~50 nm的介孔为主,大孔次之,微孔最少,但微孔是孔比表面积及孔容的主要贡献者,表明煤层气主要吸附在微孔中。(3)研究区煤层孔喉尺寸为纳米—微米级,对渗透率的贡献主要来自于亚微米—微米级的孔喉,其孔隙连通性好。煤样可动流体饱和度为38.72%~65.06%,退汞效率为0.84%~44.30%,均质系数为1.86~10.95,且不同深度煤层孔喉半径对渗透率的贡献存在较大差异,表明该区煤层具有较强的非均质性。The pore structure of coal seams has a significant influence on the adsorption and diffusion of coalbed methane.By means of gas adsorption,nuclear magnetic resonance and scanning electron microscopy,a multiscale and multi-parameter joint characterization of coal seam pore structure of Jurassic Yan’an Formation in Shenmu area of Ordos Basin was carried out to clarify the law of desorption,diffusion and seepage of coalbed methane.The results show that:(1)The coal seams of Yan’an Formation in Shenmu area have average porosity and permeability of 6.89%and 4.82 mD respectively,which belong to typical ultra-low permeability coal seams,mainly developing calcite,clay minerals and amorphous components,of which the average mass fraction is 54.8%,35.7%and 15.0%respectively.(2)The main reservoir spaces of coal seams in the study area are narrow-slit shaped and ink bottle shaped,including stomata,interchip pores,cell pores,mold pores and a few microcracks.The pores are dominated by mesoporous pores with pore size of 2-50 nm,followed by macropores,with the least amount of micropores.However,micropores are the main contributors to the specific surface area and pore volume of pores,indicating that coalbed methane is mainly adsorbed in micropores.(3)The pore throat size of coal seams in the study area varies in nano-and micron-level,the contribution to permeability mainly comes from submicron to micro pore throats,indicating that the pore connectivity in this range is good.The mov-able fluid saturation of coal samples is 38.72%-65.06%,the mercury removal efficiency is 0.84%-44.30%,the homogenization coefficient is 1.86-10.95,and the contribution of pore throat radius to permeability at different depths were significantly different,indicating strong heterogeneity in this area.

关 键 词：核磁共振 气体吸附 非均质性 微孔 孔隙结构 煤层 延安组 侏罗系 鄂尔多斯盆地 

分 类 号：TE122.2[石油与天然气工程—油气勘探] P618.13[天文地球—矿床学]