应力加载过程中页岩超声波传播特性研究  

Investigation on the propagation characteristic of shale ultrasonic in the stress loading procedure

作　　者：白佳佳 司双虎 康毅力[2] 陈明君[2] 游利军[2] 陶磊 朱庆杰 BAI JiaJia;SI ShuangHu;KANG YiLi;CHEN MingJun;YOU LiJun;TAO Lei;ZHU QingJie(School of Petroleum Engineering,Changzhou University,Changzhou 213164,China;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Southwest Petroleum University,Chengdu 610500,China)

机构地区：[1]常州大学石油工程学院,常州213164 [2]“油气藏地质及开发工程”国家重点实验室,西南石油大学,成都610500

出　　处：《地球物理学进展》2022年第6期2351-2363,共13页Progress in Geophysics

基　　金：国家科技重大专项(2016ZX05061);非常规油气层保护四川省青年科技创新研究团队(2021JDTD0017)联合资助。

摘　　要：当有效应力发生变化时,会引起页岩孔隙结构发生变化,进而影响声波在页岩中的传播特性.前人工作多关注页岩纵/横波传播速度以及二者比值对有效应力的响应特征,而对有效应力与页岩声波波形、频谱以及声强之间的关系则很少研究.以渝东南彭水地区龙马溪组富有机质页岩为研究对象,利用SCMS-J型声电测试仪,采集围压加载过程(5~55 MPa)中页岩纵/横波传播信息,分析围压加载过程中页岩声波波形、频率以及能量的变化特征.研究表明:(1)页岩纵/横波波形对有效应力的敏感程度远远高于纵/横波传播速度,随着有效应力增加,波形相似系数迅速减小;(2)有效应力加载过程中,声波对页岩选择性吸收,形心频率f_(c)随围压呈指数增加,f_(c)变化特征与页岩孔隙结构变化特征具有一致性;(3)有效应力增加时,页岩超声波散射衰减损耗变少,纵/横波平均振幅谱强度P呈指数增加.研究成果对评价页岩裂缝发育程度,准确评价页岩储层具有重要意义.When the effective stress changes,the pore structure of shale will change,which will further influence the propagation characteristic of the sound wave in the shale.In the previous studies,most attention was paid to the longitudinal/transverse propagation speed of the shale as well as the response characteristic of their specific value to the effective stress.However,few studies have been made on the relationship between effective stress and the sound wave shape,frequency spectrum and sound intensity.In this research,by taking organic rich shale in Longmaxi Formation of Pengshui area in southeastern Chongqing as research object,and used SCMS-J acoustoelectric tester,the propagation information of the longitudinal/transverse wave of the shale in confining stress loading process(5~55MPa)was adopted,this paper analyzed the change features of the sound wave shape,frequency and energy in the shale.The study shows:(1)the sensitive degree of the shale’s longitudinal/transverse shape towards effective stress is far higher than longitudinal/transverse propagation speed.With the increase of effective stress,the similarity coefficient of the wave shape decreases rapidly;(2)In the loading process of effective stress,the sound wave absorbs the shale selectively,the centroid frequency f_(c)increases exponentially together with confining pressure.The change feature of f_(c)has certain consistency with the change feature of the pore structure in a shale.(3)When the effective stress increases,the shale ultrasonic loss in scattering and attenuation declines,and the average amplitude spectrum P of the longitudinal/transverse wave presents an exponential increase.The research results are of great significance for evaluating the development degree of shale fractures and accurately evaluating shale reservoirs.

关 键 词：页岩 有效应力 声波形状 频谱 声强 

分 类 号：P631[天文地球—地质矿产勘探]