几种岩石骨架模型的适用性研究

Accuracy of dry frame models in the study of rock physics

在地震岩石物理中,Biot-Gassmann理论通常用来研究饱和流体对岩石地震特征的影响以及描述地震响应与岩石物性之间的关系.然而Biot-Gassmann理论并没有阐述多孔岩石的骨架与基质之间的关系,因此出现了各种各样的岩石骨架模型分别从不同的角度建立了岩石骨架与岩石基质之间的关系,如Krief模型、Nur模型(临界孔隙度模型)和Pride模型等都是广泛使用的岩石骨架模型.本文将这些常见的岩石骨架模型应用于Biot-Gassmann理论中,进行理论模型正演、速度预测以及Biot系数计算等,并与实验室测量数据对比,分析发现Pride模型比Krief模型和Nur模型的适用范围更广,以及Krief模型和Nur模型不能适用于低压、低孔岩石的特点.

In the study of seismic rock physics, Biot-Gassmann theory is one of the most classic and practical instruments which is used to calculate the effect of fluid saturation on seismic properties and to predict the relation between the elastic velocities and the physical properties of porous rocks. But Biot-Gassmann theory does not illuminate the relation between the moduli of the dry frame and that of the matrix. There are several models which illustrate the relation from different aspects, such as the Krief model, Nut model （critical porosity model）, Pride model, etc. They are the most popular models. We have applied the Krief model, Nur model and Pride model to Biot- Gassmann theory, through forward modelling, predicting velocity and calculating Blot coefficient, compared with core samples measured in laboratory, to check their accuracy and applicability. We found that the Pride model could work well consistently; while the Krief model and Nur model could only exhibit their applicability under normal conditions and fail in other conditions; and more importantly, the last two models could not work well when the porosity of rocks is low or the effective pressure is low.