围压下裂隙对地震波速度影响的物理实验研究

构建了等直径不同裂隙密度和等裂隙密度不同裂隙直径两组物理模型，进行不同围压条件下多方向的超声波速度测试，并运用Hudson理论进行了理论模型计算。结果显示，计算与实测结果吻合较好。随围压的增大，纵、横波速度均近线性增加，纵、横波各向异性基本保持不变；裂隙密度从2%增大到6%，纵波速度不同程度降低，其中慢纵波降低幅度相对较大，快横波变化不明显，而慢横波则大幅降低。随着裂隙密度的增大，纵、横波各向异性均增大，且横波各向异性增加速率大于纵波；裂隙直径从2 mm增大到3 mm，快纵波速度增加很小，慢纵波增加明显，横波速度均不发生改变。随着裂隙直径的增大，纵波各向异性逐渐降低，横波各向异性保持不变。最后结合试验结果分析了Hudson理论在不同深度进行参数预测的必要条件。研究结果有助于油气生产、地下水的开采与控制、污染处理等。 

STUDY ON SEISMIC PROPERTY OF CRACK-INCLUDED PHYSICAL MODEL

It is very helpful in petroleum production, groundwater exploration and to disposal of pollution to investigate the seismic property of the crustal rocks included cracks or fractures. Two group physical models with the same diameter varying crack density and the same density varying diameters were constructed. The seismic velocities were measured under different confining pressure and calculated by numerical simulation based on Hudson theory. The calculated and measured results show that the V_p and V_s nearly increase linearity and there anisotropy keep nearly stable constant with confining pressure. V_p circles decrease with the crack density varying from 2% to 6%. Moreover, the slow V_p decrease more amplitude than the fast V_p which maintains nearly stable, the V_p and V_s anisotropy all increase with the crack density ranging from 2% to 6%.With the crack diameter varying from 2 mm to 3 mm, the V_p increases, but the V_p anisotropy decreases, V_s and the V_s anisotropy nearly remain constant. Comparing the experimental and the theoretical calculated results, new conclusion of Hudson theory used in different depth was discussed, and the primary constraint of its application were analyzed. It is very helpful in petroleum production, exploration of groundwater and disposal of pollution to investigaste the seismic property of the crustal rocks with cracks or fractures.