Effects of an Off-centered Tool on Multi-component Monopole and Dipole Logging

Abstract

Recent logging tools have monopole and dipole sources in one system, and the monopole and dipole components are acquired by adding or subtracting responses at four monopole (pressure) receiver arrays at right angles. We investigate the effects of tool eccentricity on this monopole receiver array system for three different eccentricity directions. To simulate responses at each receiver array, we use the discrete wavenumber method. An off-centered dipole source produces nondipole modes as well as the dipole mode and the responses detected at each receiver array have different features as eccentricity direction varies, showing the similar pattern for both fast and slow formation. We separate the modes included in a response and compare the amplitude of each mode to the other modes. By considering responses at each array separately, we can precisely resolve the effects associated with eccentricity direction.