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Downhole acoustic surveillance of deepwater wells

Shell International E&P, Houston, USA

Alexander Sidorov and Boris Kashtan

St. Petersburg State University, Russia

Corresponding author: a_bakulin{at}yahoo.com

Deepwater production increasingly relies on a few precious wells that are complex and expensive. Success is critically dependent on our ability to understand and manage these wells, particularly at the sandface. These wells are filled with expensive "jewelry" like sand control and production allocation systems that aim at maximizing production and minimizing risk. While this smart equipment can mitigate many anticipated dangers, it can easily fail when something unexpected happens. For example, repairing a sand control system that failed due to plugging can cost US $30–40 million, while the costs of lost production due to long-term well impairment can be even higher. Lower-than-expected production is often referred to as "well underperformance" (Wong et al., 2003) and can be caused by various impairments: a plugged sand screen, contaminated gravel sand, clogged perforations, damaged formation around the wellbore or larger-scale compartmentalization. While 4D seismic can address large-scale compartmentalization, it has insufficient resolution to address near-well issues. Scarce downhole data from pressure and temperature gauges also cannot unambiguously characterize the impairment. This limits mitigation opportunities and prevents us from finding more effective drawdown strategies for high-rate, high ultimate-recovery deepwater wells. We strongly believe that geophysical surveillance in boreholes has a big role to play in identifying sources of well impairment and optimizing production. Here we describe one possible avenue—real-time completion monitoring (RTCM)—that utilizes acoustic signals in the fluid column to monitor changes in permeability along the completion. In essence, this is a miniaturized 4D seismic survey in a well. We illustrate the capabilities of acoustic surveillance through a series of full-scale laboratory tests with realistic completion and discuss opportunities for deployment in deepwater wells.