Influence of rock fractures on the amplitude of dipole-source refl ected shear wave

作者：Wang Hao,Li Ning,Wang Cai-Zhi,Wu Hong-Liang,Liu Peng,Li Yu-Sheng,Liu Ying-Ming,Yuan Ye

摘要：To identify refl ector fractures near borehole by using dipole-source refl ected-shearwave logging, we need to understand the relation between the amplitude of the refl ected shear wave and the source radiation, borehole conditions, and attenuation owing to the surrounding formations. To assess the effect of these factors on the amplitude of the refl ected waves, we first studied the radiation performance and radiation direction of the dipole source in fast, medium, and slow formations by using the asymptotic solution in the far fi eld of the borehole. Then, the relation between the fracture parameters, and the refl ected-shear-wave amplitude as well as the ratio of the refl ected-shear-wave amplitude to the direct-wave amplitude (relative amplitude, RA) was evaluated by the three-dimensional fi nite-difference (3D FDTD) method. Finally, the fracture detection capability of the dipole reflected-shear-wave logging tool in different formations was analyzed by using the RA. The results suggest that the radiation amplitude of the SH-wave in the slow formation is weaker than those in the fast and medium formations, and the amplitude of the refl ected shear wave is lower. However, the RA in the slow formation is close to or even greater than in the fast and medium formations, which means that dipole-source shear-wave logging has the same or even better fracture detection capability in the slow formation as in the fast and medium formations. In addition, when RA is small, there is a good correlation between the RA and the various fracture parameters in the different types of formation, which can be used in determining the lower limit of the fracture parameters identifi ed by refl ection logging.

发文机构：Research Institute of Petroleum Exploration & Development Yangtze University School of Earth and Space Sciences

关键词：DIPOLESOURCEreflectedSHEARwaveBOREHOLEFRACTURE

分类号： O[理学]