川南地区龙马溪组页岩岩石声波透射实验研究

为了获得对龙马溪组页岩储层声波传播特性的规律,选取川南地区下志留统龙马溪组页岩野外露头岩块,钻取不同层理角度的岩心(10个层理角度),采用透射法系统地分析了龙马溪组页岩不同层理角度的岩石纵横波速度,计算页岩岩石动弹性力学参数。研究结果表明川南地区龙马溪组页岩的纵横波速度呈显著的正线性关系,页岩岩石的纵横波速度比均值或纵波速度随层理角度的增加而减小;页岩岩石的动弹性模量、体积模量及剪切模量与岩石的纵横波速度有较好相关性,呈指数关系,而动泊松比与岩石纵波速度有良好线性相关性;声波速度随层理角度的增加或频率减小而减小,与频率呈良好的正对数关系;声波衰减系数随层理角度的增加或频率的增加而增大,与频率呈弱线性关系。

Experimental Study on Acoustic Penetration through the Longmaxi Formation Shale Rock in South Region of Sichuan Basin

To acquire the law of acoustic propagation property of the Longmaxi formation shale, we first collected the rock from shale outcrops of the Lower Silurian Longmaxi formation shale in the south region of Sichuan Basin, cores were drilled from different bedding angle(ten bedding angles), meanwhile the P-wave velocity and S-wave velocity of Longmaxi formation shale were studied using acoustic penetration experiments in the laboratory, and the dynamic elasticity parameters of shale rock were computed. The result shows that there is linear relation between P-wave velocity and S-wave velocity of the Longmaxi formation shale in the south region of Sichuan Basin. The average values of the Vp/Vs ratio and P-wave velocity of shale rock decreased with increasing in the bedding angle. There exists exponential relation between dynamic modulus, shear modulus and volumetric modulus and P-wave velocity or S-wave velocity, whereas the Poisson ratio values were liner correlated with P-wave velocity. With the increase of the bedding angle or the decrease of the frequency, the wave velocity decreases, and there is positive relationship between acoustic velocity and frequency. While the attenuation coefficient increases with the increase of the bedding angle or the increase of the frequency, and which were weakly correlated with frequency.