Acoustic field in a cased well with a sectorial crossing channel

Abstract

The crossing channel in a cased well is a vertical and sectorial column filled with fluid in the cement layer between the steel pipe and formation sometimes formed during well cementing, which is harmful to the well and must be detected. To study the possibility of detecting the crossing channel by using a traditional logging tool, an acoustic field generated by a monopole source in a cased well with a crossing channel of various angles is simulated by a 2.5-D finite difference method for the first time. The results of the 2.5-D finite-difference method for the cases of 0 or 360 deg are compared and consistent with that of the well-known real axis integration method. Snapshots of normal stress and synthetic time-domain waveforms are displayed. The 2-D spectrum in wave number and frequency domain is also calculated, where the influence of the channel is clearer than that in the waveforms. Numerical study demonstrated that a crossing channel can be detected and sized if its angle is greater than 30 deg, and larger offset and lower frequency source are favorable to detect and size the crossing channel. [Work supported by NSFC 19974059.]