Nonlinear Semblance Processing For The Evaluation Of An Acoustic Altered Zone Around The Borehole
Name
1994.10 Tezuka.pdf
Size
382.71 KB
Format
Adobe PDF
Checksum (MD5)
f4ef89fc770fe275f333054c096d7aa3
Author(s)
Tezuka, Kazuhiko
Date Issued
1994
Publisher
Massachusetts Institute of Technology. Earth Resources Laboratory
Series/Report no.
Earth Resources Laboratory Industry Consortia Annual Report;1994-10
Abstract
This paper describes a simple method to evaluate an acoustic altered zone around the
borehole using an array of sonic waveforms. The method is based on a semblance velocity
analysis and a nonlinear travel time window is introduced. On the assumption that a
velocity gradient of the altered zone may be linear, the nonlinear travel time window is
calculated as a function of averaged velocity and a normalized velocity gradient. The
method is applied to the synthetic acoustic data calculated by finite difference modeling. Case studies with several altered formation models confirmed that this method is a good estimator of the velocity gradients around the borehole.
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