The amplitude of shear waves is attenuated when passing through horizontal fractures crossing a borehole. In this study, we investigate the amplitude attenuation of shear waves throughout simulation of full-wave acoustic logging with the finite-difference method. As the fracture aperture is very small, it needs to be represented in a very fine gird when carrying out finite-difference simulation. Therefore, the variable-grids finite-difference method is adopted to avoid over-sampling in the non-fracture regions, yielding substantial savings in computational cost. We demonstrate the accuracy of waveform modeling with the variable-grid finite-difference by benchmarking against that obtained with the real-axis integrating method. We investigated the effects of several important parameters including fracture aperture, distance from receiver to fracture, borehole radius and extended distance utilizing that benchmarked variable-grid finite difference code. We determined a good linear relationship between the attenuation coefficient of shear wave amplitude and the fracture aperture. Then, the effects of distance from receiver to fracture, the borehole radius and the extended distance of fracture on shear wave attenuation are also studied. The attenuation coefficient of shear wave becomes smaller with the increasing borehole radius. While, it increases as the distance from receiver to fracture and the extended distance of fracture increase. These effect characteristics are conducive to the use of shear wave to evaluate fractures.

当横穿穿过井眼的水平裂缝时，剪切波的振幅会衰减。在这项研究中，我们通过有限差分方法在全波声波测井的整个模拟过程中研究了剪切波的振幅衰减。由于裂缝孔径非常小，因此在进行有限差分模拟时需要以非常精细的网格表示。因此，采用可变网格有限差分法来避免在非断裂区域中进行过采样，从而节省了计算成本。我们通过对实轴积分方法获得的基准进行基准测试，证明了可变网格有限差分法的波形建模的准确性。我们研究了几个重要参数的影响，包括裂缝孔径，从接收器到骨折的距离，利用该基准可变网格有限差分代码来确定井眼半径和延伸距离。我们确定了剪切波振幅的衰减系数与裂缝孔径之间的良好线性关系。然后，研究了从接收器到裂缝的距离，井眼半径和裂缝的扩展距离对剪切波衰减的影响。随着井眼半径的增加，剪切波的衰减系数变小。同时，它随着从接收器到骨折的距离以及骨折的延长距离的增加而增加。这些作用特征有利于利用剪切波来评估裂缝。我们确定了剪切波振幅的衰减系数与裂缝孔径之间的良好线性关系。然后，研究了从接收器到裂缝的距离，井眼半径和裂缝的扩展距离对剪切波衰减的影响。随着井眼半径的增大，剪切波的衰减系数变小。同时，它随着从接收器到骨折的距离以及骨折的延长距离的增加而增加。这些作用特征有利于利用剪切波来评估裂缝。我们确定了剪切波振幅的衰减系数与裂缝孔径之间的良好线性关系。然后，研究了从接收器到裂缝的距离，井眼半径和裂缝的扩展距离对剪切波衰减的影响。随着井眼半径的增大，剪切波的衰减系数变小。同时，它随着从接收器到骨折的距离以及骨折的延长距离的增加而增加。这些作用特征有利于利用剪切波来评估裂缝。随着井眼半径的增加，剪切波的衰减系数变小。同时，它随着从接收器到骨折的距离以及骨折的延长距离的增加而增加。这些作用特征有利于利用剪切波来评估裂缝。随着井眼半径的增加，剪切波的衰减系数变小。同时，它随着从接收器到骨折的距离以及骨折的延长距离的增加而增加。这些作用特征有利于利用剪切波来评估裂缝。