Abstract:

Complex structure of cracked media has been a key research resource prospecting object due to the fact that it hides huge reserves. Based on Hudson’s crack theory, responses of different well diameters in cracked medium with different crack parameters (number density, angle and aspect ratio) are simulated. Results show that when crack number density is small, compressional, shear and Stoneley wave amplitudes are sensitive to the variation of well diameter; when the crack angle is big, Stoneley wave amplitude is sensitive to the variation of well diameter; when the crack angle is small, shear wave amplitude is sensitive to the variation of well diameter; when crack aspect ratio is small, compressional, shear and Stoneley wave amplitudes are sensitive to the variation of well diameter; in two-dimensional spectrum the multi-mode wave’s initial excitation frequency becomes smaller as well diameter increases; the frequency band of the maximum excitation intensity will move to low frequency as well diameter increases. It is clear that the propagation of elastic wave in cracked medium is affected by well diameter and crack parameters, and obeys certain regularity. Applying Hudson’s crack theory to simulate the cracked medium at well-site can be used to systematically analyze the well-site response of cracked media. The results of this study can give a guide for field logging work in the case of cracked media.

Key words: cracks, Hudson’s crack theory, well diameter, acoustic logging