Eni operates subsea wells in two deepwater gas fields located off the Indonesian coast. Maximum well deviations reach up to 70°, and all the wells are tied back to one floating production unit (FPU).
Each well produces gas from two or more sands. Field A uses intelligent completions for independent control of the production from upper and lower zones to manage reservoir pressure decline rates and minimize the effect of water coning and solids production. Field B, on the other hand, was planned with conventional wells, but the completion design had to be revised when the first well encountered the GWC. Because the FPU was not designed to handle high water cuts, water production requires careful management and consequently, on-off valves are unsuitable for zonal flow control. Interventionless valve actuation is another important requirement for the remote subsea fields.
SLB proposed deploying two multiposition ICVs in each well—an annular valve to control flow (from the upper zone) between the tubing and annulus and an inline one to control flow (from the lower zone) inside the tubing. Each valve has eight positions, including fully open and closed, and a dedicated hydraulic control line operated from surface is used to open the valve. The closed line is shared by both valves in the well. Production from each reservoir interval can hence be controlled independently and remotely, without requiring intervention with wireline or CT. These valves have also been deployed in Field A and were therefore familiar to Eni.
Despite the disruptions caused by the COVID-19 pandemic, early collaboration between the two companies enabled expedited deployment of equipment and expert personnel for Field B as well as timely preparation for a range of contingencies that could arise (e.g., 7-in and 9⅝-in cased hole gravel packs). Local crews were specially trained for the complex operations, which were completed without HSE incidents. The professionalism of SLB offshore personnel was commended in writing by Eni management. Closing the ICVs from surface eliminated the need to install a plug before increasing pressure to set the upper completion packer, an added benefit that saved rig time.
Sand control technologies deployed across these unconsolidated formations ensure the durability of the ICVs, and the valves have easily withstood the production rates in Field A. In Field B, however, Eni increased its daily production target by about 45% when the ability of the wells to deliver at high flow rates became apparent. Valve installation was already complete, and erosion of the annular valve was a concern at the higher rates. SLB worked closely with Eni to conduct extensive simulations that confirmed the valves’ flexibility and ability to withstand the revised flow rates.
Remote monitoring of downhole pressures and temperatures and selective zonal flow control are helping maximize production cost efficiently, with the optimal well count. Using the adjustable ICVs to optimize zonal contributions has the potential to avoid—or at a minimum, delay—water production, based on geological and geophysical interpretation, and enable an optimal depletion strategy.
