岩性、孔隙及其流体变化对岩石弹性性质的影响

Influence of lithology,porosity and variation of pore fluid saturation on rock elastic property

李生杰

Li Shengjie

根据Gassmann方程推导出了流体模量与含流体岩石体积模量之间的关系。该关系反映出在流体置换过程中,流体模量及岩性变化等因素对含流体岩石弹性性质的影响。通过理论计算与分析表明,流体变化对刚性较强的(硬)岩石影响较小,而对刚性较小的(软)岩石影响较大。岩石孔隙度越低,含流体岩石体积模量对流体变化愈敏感。即地震波的纵波速度随孔隙度增大而减小。岩石孔隙度及流体模量较小时,纵波速度对流体变化比较敏感。通过对实际岩石样品进行流体驱替实验,发现实验结果与理论分析相一致。

A relational expression between fluid modulus and bulk modulus of fluid-bearing rocks is derived based on the Gassmann's equation.It reflects the influences of such factors as fluid modulus and lithology on the elastic properties of fluid-bearing rocks in the process of fluid displacement.Theoretical calculation and analysis show that fluid variation has relatively small influences on rocks with relatively large rigidity(hard),and has relatively large influences on rocks with relatively small rigidity(soft).The lower the rock porosity is,the more sensitive the bulk modulus of fluid-bearing rocks is to fluid variation,i.e.,the compressional velocity of seismic wave decreases with increasing rock porosity.When rock porosity and fluid modulus are relatively small,compressional velocity is relatively more sensitive to variation of fluid saturation.The results of fluid displacement experiments in real rock samples agree with the theoretical analysis.

10.11743/ogg20050611