利用实验室加压条件下声速测量数据估计岩石裂隙参数

Estimating the Rock Crack Parameters from the Velocity Data Under Pressure Loading in the Laboratory

针对实验室加压条件下岩石在干燥和流体饱和状况下的声速测量数据,利用多参数反演算法得到了不同压力下岩石的裂隙密度和裂隙纵横比。反演得到的裂隙密度和裂隙纵横比随着压力的变化趋势很好地说明了实验室速度随着压力的变化趋势,随着压力的增加,裂隙密度逐渐减小,裂隙纵横比逐渐增大。将反演得到的裂隙密度和裂隙纵横比代入孔隙、裂隙介质模型,预测的速度数据与实测的数据吻合良好,表明所采用的反演方法可以较好地从实验室加压下的声速测量数据中估计岩石的裂隙发育状况。

The characterization of cracks in tight formations is very important for the exploration of this kind of reservoirs. In the cracked porous media elastic wave theory, crack density and aspect ratio can significantly affect the elastic wave velocities. The crack parameters can be obtained by inverting the velocity versus pressure data of dry and fluid-saturated rocks measured in the laboratory. The inversion results can also be used to simulate and predict the acoustic velocities of the rock with a different fluid. To demonstrate this technique, this paper shows the estimated crack parameters of specific rock examples. The variation trends of crack density and aspect ratio versus pressure predict the velocity variation with pressure quite well, showing that the velocity increase with pressure is the result of crack closure under pressure. The inversion examples show the validity of the technique for estimating crack parameters from laboratory velocity data.