气饱和孔洞型介质动静参数关系的数值模拟研究

采用实验手段研究岩石的动、静弹性参数的变化规律及动、静态参数间的相互关系时存在着测试成本高,工作量大,普适性差且可靠性较低等问题.对岩样在单轴压缩加载条件下的破坏过程,采用岩石破裂过程分析RFPA系统进行数值模拟,获取岩样的应力—应变曲线可计算得到静态弹性参数.从弹性波动理论出发,采用交错网格有限差分方法,对超声波透射实验进行数值模拟,获取纵、横波速度可计算得到动态弹性参数.对50块不同的气饱和孔洞型岩样同步计算其动、静态弹性参数,并分析动、静态弹性参数随孔隙度的变化规律及动、静态弹性参数间的关系.结果表明:动弹性模量大于静弹性模量,且二者之间的线性关系良好,而动、静泊松比之间不存在明显的相关关系.该项研究为动、静弹性参数关系研究提供了新的方法,研究结果对于指导储层预测、油气检测以及地震资料综合解释都有重要的意义.

Numerical simulation study on relationship between dynamic and static elastic parameters of gas saturated porous media

There are many problems such as high cost,heavy workload,poor universality and low reliability when studying the change rules of dynamic and static elastic parameters and the relationship between dynamic and static parameters of rocks by means of experiment.The RFPA system can be used for numerical simulation of rock failure process under uniaxial compression loading.The stress and strain curves of rock samples are obtained,and the static elastic parameters can be calculated.Based on elastic wave theory,by using staggered grid finite difference method,the numerical simulation of acoustic characteristic experiment is carried out.The P-wave and S-wave velocities are obtained,and the dynamic elastic parameters can be calculated.The dynamic and static elastic parameters of 50 different gas saturated porous rock samples are calculated synchronously,and the variation laws of static and dynamic elastic parameters changing with porosity and the relationship between dynamic and static elastic parameters are analyzed.The results show that the dynamic elastic modulus is larger than the static elastic modulus,and the linear relationship between them is good,but there is no obvious correlation between the dynamic and static Poisson's ratio.A new method for the study of relationship between dynamic and static elastic parameters is provided.The results can provide test data support for in-depth study of rock deformation and failure laws and engineering safety and reliability.