Analysis of radial detection characteristics of monopole sonic logging

Abstract

Drilling causes variation of the rock properties in the vicinity of a wellbore. In this article, we use the radial cylindrical layered model to examine monopole logging response with a two-dimensional axisymmetric finite difference method. Three variables are set, that is, the transition zone thickness, the source frequency and source-receiver spacing, respectively. We also use the slowness-time correlation-method to evaluate sound speed variations under different conditions. At last, based on the ray theory, the variation characteristics of the arrival time of the first wave under different conditions are analyzed. We conclude that the radial detection characteristics of compression waves are greatly affected by spacing. By combining different signals with various spacings, it is possible to obtain the tomography of the compressional wave velocities near wellbore.