水化作用下页岩微观孔隙结构伤害特征  

Damage of Hydration Effect to Micropore Structure of Shale

作　　者：余致理 郭高峰 余恒 李庆[1] 张艳玲[1] YU Zhili;GUO Gaofeng;YU Heng;LI Qing;ZHANG Yanling(Chongqing Gas Field,PetroChina Southwest Oil & Gas Field Company,Chongqing 400021,China)

机构地区：[1]中国石油西南油气田分公司重庆气矿,重庆400021

出　　处：《西安石油大学学报（自然科学版）》2022年第1期44-50,100,共8页Journal of Xi’an Shiyou University（Natural Science Edition）

基　　金：国家科技重大专项“鄂尔多斯盆地大型低渗透岩性地层油气藏开发示范工程”(2016ZX05050)。

摘　　要：为明确压裂过程中水化作用对页岩微观孔隙结构的伤害特征,选取渝西地区龙马溪组页岩,通过扫描电镜、低场核磁共振和单黏土矿物水化实验,在对比蒙脱石和伊利石的单矿物水化特征的基础上,研究了页岩T_(2)谱分布变化特征,并建立了水化伤害程度评价指标,定量分析了页岩水化过程中微观孔隙结构的伤害特征。研究结果表明,黏土矿物水化后,易于在晶体表面形成水化膜,降低了岩石骨架颗粒间的引力与胶结强度,造成颗粒松动、脱落和运移。蒙脱石水化后的膨胀体积、膨胀应力和线性膨胀率均大于伊利石,其中应力膨胀的滞后性是导致微观孔隙结构变化的主要原因。水化伤害程度随浸泡时间的增加先快速增加后趋于稳定,而水化作用下的微裂缝则扩展延伸后趋于闭合。In order to clarify the damage characteristics of hydration on the micro pore structure of shale during fracturing,through scanning electron microscope,low field NMR and single clay mineral hydration experiments,based on the comparison of thehydration characteristics of montmorillonite and illite,the variation characteristics of T_(2) spectrum distribution of shale in Longmaxi Formation in Western Chongqing were studied,the evaluation index of hydration damage degree of the shale was established and the damage characteristics of shale micro pore structure caused by hydration process are analyzed quantitatively.The results show that after hydration,clay minerals are easy to form hydration film on the crystal surface,which reduces the gravitation and cementation strength between rock skeleton particles,resulting in particle loosening,falling off and migration.The expansion volume,expansion stress and linear expansion rate of montmorillonite after hydration are greater than those of illite,and the hysteresis of stress expansion is the main reason for the change of micro pore structure of shale.The degree of hydration damage first increases rapidly and then tends to be stable with the increase of immersion time,while the micro cracks in shale will expand first and then tend to closed under hydration.

关 键 词：页岩微观孔隙 水化作用 膨胀 微裂缝 

分 类 号：TE349[石油与天然气工程—油气田开发工程]