重庆綦江地区龙马溪组页岩孔隙特征与页岩气赋存关系探讨  

Pore Characteristics and Relation with Shale Gas in the Longmaxi Formation Shale Reservoir

作　　者：刘宇[1,2] 夏筱红[1,2] 李伍[1,2] 李家宏[1,2] 

机构地区：[1]中国矿业大学资源与地球科学学院,江苏徐州221116 [2]中国矿业大学煤层气资源与成藏过程教育部重点实验室,江苏徐州221008

出　　处：《天然气地球科学》2015年第8期1596-1603,共8页Natural Gas Geoscience

基　　金：国家基础研究发展计划项目(编号:2012CB214702);国家自然科学基金(编号:41272155);煤层气资源与成藏过程教育部重点实验室(中国矿业大学)开放基金资助项目(编号:2015-004)联合资助

摘　　要：通过高压压汞实验、低温氮气吸附实验、氩离子抛光一扫描电子显微镜观测对重庆綦江地区龙马溪组页岩样品进行了储层表征，并结合分子势能理论揭示了龙马溪组孔隙与页岩气赋存的关系。研究表明：①龙马溪组页岩储层中以小于100nm的孔隙最为发育，比表面积主要由半径小于8nm的孔隙提供，且纳米级孔隙以有机质孔为主，孔表面普遍存在不光滑性，具有分形特征，大孔孔壁叠合成诸多小孔。②有机质孔中甲烷分子与孔壁距离小于2nm时，二者间具有较强相互作用力；大于2nm时，二者间相互作用力可以忽略，甲烷分子呈游离状态。③龙马溪组储层孔隙中吸附气体积随孔径的增大而减少，当半径大于30nm时，吸附气体积可以忽略；游离气体积呈先增大后减小的趋势，在半径45nm附近达到顶峰。在10nm附近游离区域体积开始大于吸附区域体积；1-75nm孔隙中吸附区域占此孔径范围内孔隙总孔容的66％-71％。By using high pressure mercury,low temperature nitrogen adsorption,argon ion polishing-scanning electron microscope observation,the reservoir of Longmaxi Formation shale samples has been characterized.Combined with the molecular potential energy theory,the relationship between the Longmaxi Formation porosity and shale gas occurrence has been revealed.The research shows that：（1）Pores smaller than 100 nm are most developed in the Longmaxi Formation shale reservoir,and the specific surface area is mainly provided by pore radius smaller than 8nm,and nano-pores are mainly organic matter pores.Those pores are not smooth,and have fractal characteristics.The surface of bigger pores has superimposed many small pores.（2）When the distance between CH4 and pore wall is shorter than 2nm,there are strong interactions between the two and when the distance is longer than 2nm,the interactions can be ignored,and the CH4 is in a free state.In pores larger than 2nm,adsorption capacity is proportional to the specific surface area,but in pores smaller than 2nm,average concentration has a great relationship with the aperture.（3）In the reservoir of Longmaxi shale,the volume of adsorbed gas decreases with increasing pore size,and when the radius is larger than 30 nm,the volume of adsorbed gas can be ignored.Volume of free gas first increased and then decreased with increasing pore size.It reached a peak in the vicinity of 45 nm.In the vicinity of the 10 nm,free gas volume became more than adsorbed gas volume;In pores with radius smaller than75 nm,adsorption region accounts for 66%-71% of the total.

关 键 词：龙马溪组 孔隙 气体赋存 孔隙模型 

分 类 号：TE122.2[石油与天然气工程—油气勘探]