Real-Time Completion Monitoring Estimates Production Impairment With Acoustics Waves

Abstract

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 less expected happens. For example, repairing a sand control system failed due to plugging can cost US$30-40 million. Costs of lost production due to long-term well impairment can be much higher. Lower than expected production is often referred to as "well underperformance" 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. Scarce downhole data from pressure and temperature gauges cannot unambiguously characterize the impairment and 4D seismic has no resolution to address near-well issues. 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. These signals are carried by tube waves that move borehole fluid back and forth radially across the completion layers. Such tube waves are capable of "instant" testing of the presence or absence of fluid communication across the completion and are sensitive to changes occurring in sand screens, gravel sand, perforations, and possibly reservoir. The part of the completion that has different impairment from its neighbors will carry tube waves with modified signatures (velocity, attenuation). We illustrate capabilities of acoustic surveillance through a series of full-scale laboratory tests with a realistic completion and discuss opportunities for deployment in deepwater wells. Thus real-time completion monitoring could be thought of as "miniaturized" 4D seismic and "permanent log" in an individual wellbore. MotivationCompletions lie at the heart of deepwater production and present a large portion of the overall well cost. Great multidisciplinary effort is invested upfront to design them right. This contrasts with the production stage where little information is available to detect problems, optimize the inflow and prevent expensive workovers. Incomplete gravel packing, development of "hot spots" in screens, destabilization of the annular pack, fines migration, sand screen plugging, near-wellbore damage, crossflow, differential depletion, compartmentalization, compaction represent a typical list of challenges that are extremely difficult to decipher ba...