砂岩岩石力学参数各向异性研究

On the Rock Mechanics Parameters Anisotropy of Sandstone

对胜利油田不同深度的四口井的砂岩岩芯进行了三轴压缩试验和动态岩石力学参数试验。根据获得的垂直地层方向和平行地层方向的试验数据,计算了各岩石力学参数的各向异性系数。通过分析围压以及深度对各向异性系数的影响,给出了砂岩峰值强度各项异性系数、静泊松比各向异性系数、纵波波速各向异性系数、纵横波速比和动泊松比各向异性系数与深度的拟合公式。发现峰值强度、纵波波速和纵横波速比的各向异性系数都随着深度的增加而减小,而泊松比各向异性系数随着深度的增加而增大。动、静弹性模量各向异性系数与深度相关性都很差,动弹性模量各向异性较弱,静弹性模量相对较强。

Triaxial compression test and dynamic rock mechanics parameters test were conducted for sandstone cores collected from four oil wells with different depths at Shengli Oilfield. Anisotropic coefficients of rock mechanics parameters were calculated based on the obtained experimental data of the vertical direction to strata and the parallel formation direction. Through analyzing the influence of the confining pressure and the depth on anisotropic coefficient, the fitting formulae between anisotropic coefficient and depth were presented, including the anisotropic coefficient of peak strength, the anisotropic coefficient of static Poisson＇s ratio, the anisotropic coefficient of longitudinal wave speed, the vertical and horizontal wave velocity ratio, the anisotropic coefficient of dynamic Poisson＇s ratio, etc. It is found that the anisotropic coefficients of the peak strength, the longitudinal wave speed and the vertical and horizontal wave velocity ratio decrease with the increase of depth, but the anisotropic coefficients of Poisson＇s ratio present converse trend. The correlation among dynamic and static elastic modulus and depth is poor. The anisotropy of dynamic elastic modulus is weaker than that of static elastic modulus.