Optimized Completions Design Using Retrofit Autonomous Inflow Control Devices

Abstract

Discovered in 1964, the Beta Field in the Niger Delta sedimentary basin consists of 25 stacked hydrocarbon-bearing reservoirs located between 5,500 and 12,000 feet true vertical depth subsea (TVDSS). A total of 26 wells have been drilled in the field, of which 11 are presently on production. Oil production peaked at 8,900 stock-tank barrels per day shortly after field start-up and has been on the decline. More than 40 years since production start-up, the Beta Field remains a relatively immature, distinctly underdeveloped asset. Only about 59 million stock tank barrel (STB), or 8% of its estimated stock-tank oil initially in place of 740 million STB, had been produced by the end of 2017. Two horizontal wells were planned in the field to provide additional drainage points and increase field production. However, a production forecast of the planned wells showed potential early water breakthrough and high water cut because of unfavorable mobility ratios of a slightly viscous oil and proximity to oil/water contact (OWC). To mitigate the production challenges and improve the reservoir sweep, autonomous inflow control devices (AICDs) were selected to be installed on the sandface completion. These wells were drilled and completed during the COVID-19 pandemic, bringing additional challenges in equipment availability and logistics with potential to derail the successful completion of these wells within the required timeline. An innovative retrofit screen design, leveraging detailed engineering design and remote collaboration, enabled the conversion of ICD sand control screens to cyclonic AICD screens. AICD nozzle placement was optimized using a reservoir-centric workflow that integrates the full reservoir model with the sandface completion. Real-time interpretation of the data enabled computation of porosity-permeability and saturation estimates from logging-while-drilling (LWD) logs, which was then used in updating the reservoir model in near-real time. Using a segmented well modeling approach and a refined flow distribution from heel to toe, AICD nozzle placement was optimized in real time utilizing LWD measurements from open hole along the horizontal drain, aiding the design and configuration of the AICDs. The Beta-7 and Beta-8 wells were successfully drilled, completed, and put on production. The horizontal drains were landed within 5 to 10 feet of the top of the reservoir, maintaining at least 20-ft distance from the OWC. The forecasted simulation showed possible water influx from the toe of the horizontal as opposed to the heel because of existing water leg and high permeability at the toe. This was supported by high water-cut production from that zone in the nearby wells. This insight from the full-field simulation model enabled an informed decision on the AICD design.