孔隙、裂隙介质弹性波理论的实验研究

近年来发展起来的“孔隙、裂隙介质弹性波理论”提高了人们对实际岩石声学性质的模拟和预测的能力.作为对这一理论的实验验证和重要应用，我们将它用来模拟和解释岩石超声实验中测得的干燥和饱和岩石弹性波速度随压力的变化曲线.理论模拟的重要参数，如岩石的裂隙密度等是从实验数据反演得到的.结果表明：无论是孔隙度较高的砂岩，还是孔隙度很小的致密岩石，如花岗岩，该理论都能很好地描述岩石在干燥和饱和状态下纵、横波速度随压力的变化.造成波速变化的原因是岩石中裂隙在压力作用下的闭合和裂隙密度的减少.本文的结果还指出了将岩石裂隙密度作为描述岩石的重要物性参数，并给出了从实验室超声测量中确定这一参数的方法.

Laboratory study of elastic wave theory for a cracked porous medium using ultrasonic velocity data of rock samples

The recent development of the elastic wave theory for a cracked porous medium significantly enhances our ability to model and predict acoustic response of real rocks. As an important application and verification of the theory, we apply it to model and interpret laboratory ultrasonic velocity data of rock samples measured under pressure loading conditions. The important model parameters, such as crack density and aspect ratio, are obtained by inverting the velocity versus pressure data. The results show that the theory can well describe the elastic velocity variation with pressure under dry and saturated conditions. The theory is applicable for both porous sandstone and very tight granite. The cause of the velocity variation with pressure is the closure of microcracks and the decreasing of crack density within the rock under pressure loading. This paper also suggests using crack density as an important rock property parameter and provides a method for determining the crack parameter.