粗糙裂缝对井眼声波传播的影响

Data Influence of Rough Crack on Borehole Acoustic Wave Propagation

由于天然裂缝并非光滑裂缝,在通过声、电成像对裂缝进行识别过程中,如果将裂缝视为光滑裂缝,将会产生误差。斯通利波反射系数对裂缝宽度具有较高的灵敏度,常用斯通利波识别裂缝。分别采用物理实验和数值模拟的方法来研究粗糙裂缝对声波响应的影响,在实验方面,进行了模型井裂缝粗糙度实验,得到了粗糙裂缝的裂缝宽度和衰减系数之间的关系。对水平裂缝井眼模型进行数值模拟,研究正弦形状的粗糙裂缝对斯通利波的影响。采用迂曲度对裂缝表面的粗糙程度进行描述。实验结果显示随着裂缝表面刻槽的增加,斯通利波的衰减系数也会增加。模拟结果显示粗糙裂缝的宽度越小,和同样宽度的光滑的裂缝衰减系数之间的差距越大。通过拟合建立了斯通利波衰减系数与裂缝宽度、迂曲度的关系式。

Because natural cracks are not smooth cracks, in the process of identifying cracks by acoustic and electrical imaging, if cracks are regarded as smooth cracks, errors will be generated. Stoneley wave reflection coefficient has high sensitivity to crack width, and stoneley wave is often used to identify cracks. Physical experiment and numerical simulation were used to study the influence of rough fracture on acoustic response. In the aspect of experiment, the crack roughness experiment of model well was carried out, and the relationship between crack width and attenuation coefficient of rough crack was obtained. Numerical simulation of horizontal crack borehole model was carried out to study the influence of sinusoidal rough crack on stoneley wave. The roughness of crack surface was described by tortuosity. The experimental results show that the attenuation coefficient of stoneley wave will increase with the increase of notch on the crack surface. The simulation results show that the smaller the width of rough crack, the larger the gap between the attenuation coefficient of smooth crack and the same width. The relationship between stoneley wave attenuation coefficient and crack width and tortuosity is established by fitting.