Modeling acoustic response of permeability variation in deepwater wells using spectral method.

Abstract

Petroleum production in deepwater oil fields often hinges on the ability to safely complete and effectively draw down a small number of very challenging wells. The success of this operation requires regular completion monitoring, which is most effectively achieved using real‐time surveillance tools. Real‐time completion monitoring with acoustic waves (RTCM) has great potential for diagnosing problems in sand‐screened deepwater completions. RTCM uses tube waves to detect permeability changes and passive noises to characterize perforation flow. Interaction of a single tube wave with permeable formations in open boreholes is well explained by Biot’s theory of poroelasticity. However, experimental studies in laboratory models of sand‐screened completions reveal existence of two tube wave modes: fast and slow, supported by completion and sand screen, respectively. Development of quantitative monitoring methodology of acoustic surveillance requires better understanding on how signatures of fast and slow tube waves depend on completion properties. To this end, we simulate two tube dispersion and attenuation by examining the solutions of Biot’s equations of poroelasticity in cylindrical structures using a spectral method. The results show dependence of the velocity and attenuation of both tube waves on completion permeability. These modeling results are in a qualitative agreement with laboratory experiments.