微观孔隙结构对页岩应力敏感影响的实验研究  

Experimental Study on Microscopic Pore Structure Controls on Shale Permeability under Compaction Process

作　　者：张睿[1,2] 宁正福[1,2] 杨峰[1,2] 赵华伟[1,2] 杜立红 廖新维[1,2] 

机构地区：[1]中国石油大学(北京)油气资源与探测国家重点实验室,北京102249 [2]中国石油大学(北京)石油工程教育部重点实验室,北京102249 [3]中国石油华北油田,河北任丘062552

出　　处：《天然气地球科学》2014年第8期1284-1289,共6页Natural Gas Geoscience

基　　金：高等学校博士学科点专项科研基金项目"页岩储层多尺度耦合渗流规律研究"(编号:20120007110012);教育部科学技术研究重大计划"页岩气流动机理与产能预测模型研究"(编号:311008)联合资助

摘　　要：研究页岩储层在开发过程中的应力敏感对产能评价具有重要意义。通过脉冲法测量了渝南下寒武统牛蹄塘组2块页岩岩心的应力敏感曲线,应用毛管理论推导了毛管半径随有效应力变化的关系式,结合扫描电镜图像分析了孔径变化对应力敏感的响应特征。最后采用低温液氮吸附实验研究了页岩的微观孔隙结构特征,同时对毛管半径应力敏感公式进行了验证。研究结果表明:该地区2块页岩岩样均体现出强应力敏感,其渗透率随有效应力的变化符合指数关系式;毛管半径随有效应力的变化同样符合指数关系,孔隙越容易被压缩,毛管半径保留率越低,应力敏感越强;低温液氮吸附实验结果验证了毛管半径应力敏感公式的有效性,表明了在MK64-2岩样中,大孔比例较少,压缩过程中平均毛管半径保留率更低,小孔的比例较高,其压缩后提供给大孔的渗流通道较少,因此该岩样应力敏感性更强。The investigation of stress sensitivity is of primary importance during the life cycle of a shale gas reservoir. Pulse-decay permeability was measured for two shale samples in Niutitang Formation with in- creasing effective stres. The relationship between capillary radius and effective stress was obtained based on capillarity theory. The pore throat geometry and pore size distribution are further investigated by Scanning Electron Microscope （SEM） and nitrogen adsorption test. The results demonstrated that the exponential correlation fit the permeability stress curves well. Effective pore sizes will decrease dramatically under stress,which leads to a decrease （more than 80%） of effective permeability in shale. Further, once the strong stress is applied, only the large sized throats can be effectively retained. The small sized pores are more sensitive to the applied stress than the large one. It is probably because those micro-sized channels/ pores will firstly close. As a result, the slot shaped nano-sized pores in shale reservoirs can lead to severe stress sensitivity according to the distorted characteristics, which favors the use of nitrogen adsorption method to verify capillary radius-pressure relation.

关 键 词：页岩 应力敏感 孔隙结构 毛管模型 

分 类 号：TE132.2[石油与天然气工程—油气勘探]