基于碳酸盐岩裂缝岩石物理模型的横波速度和各向异性参数预测

高角度缝隙充填的碳酸盐岩储层可以等效为具有水平对称轴的横向各向同性介质.本文提出了适用于裂缝型碳酸盐岩的岩石物理模型构建流程,重点介绍了在碳酸盐岩各向同性背景中,综合利用微小裂隙模型和线性滑动模型添加缝隙系统,并分析了当缝隙充填不同流体时,各向异性参数随纵横波速比的变化特征.同时本文讨论了裂缝密度和缝隙充填流体对地震反射系数的影响,推导了不同类型流体充填时储层反射系数与裂缝密度的近似关系式,阐述了各向异性流体替换理论,最终实现饱含流体碳酸盐岩裂缝储层的纵横波速度和各向异性参数的估测.选取某碳酸盐岩工区A井对该方法进行试算,结果表明基于碳酸盐岩裂缝岩石物理模型估算的纵横波速度值与测井值吻合较好,而且估测所得的各向异性参数值也能够较好地反映出裂缝储层位置.

Estimation of S-wave velocity and anisotropic parameters using fractured carbonate rock physics model

Carbonate rocks with high angle fractures can be equivalent to HTI media (Horizontal Transverse Isotropic). This paper put forward the flowchart to integrate rock physics model in layered fractured carbonate rocks. It focused on the study of jointing cracks and fractures into the isotropic background media by Hudson's model and Schoenberg's model, and made an analysis of anisotropic parameters variation with P wave to S wave velocity ratio when fracture filled with different fluids. The next step was to show the influence which was induced by fractures density and fracture fluid on seismic reflectivity coefficient. And it also aimed to accomplish fluid filling work in fractures space using Brown and Korringa's generalized Gassmann equations. Then we calculated P wave, S wave velocity and anisotropic parameters in carbonate rocks which jointed fractures and saturated fluid. At last, the paper discussed the accuracy of the parameters estimation method based on fractured carbonate rock physics model. The estimated S-wave velocity was consistent with the log value. And the estimated anisotropic parameters could describe the fractured reservoir location.