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This paper describes the successful application of Autonomous Inflow Control Device (AICD) technology in the Nong Yao oil field located in Block G11/48 within the Gulf of Thailand. Water injection in the Nong Yao field, is often into unconsolidated sands drained at different depletion levels. This can lead to formation failure and the transportation of sand back through the annulus and tubing. This AICD bypass valve technology provides a solution by only allowing injected water into the formation but not in the opposite direction hence preventing downhole crossflow. An AICD Bypass Valve was installed into two injection wells that were completed as Multi Zone Completions (MZC). It was planned that multiple zones would be opened simultaneously to provide ongoing waterflood support. The expectation was that the AICD technology would prevent crossflow between zones, due to pressure difference during any injection shutdowns, thereby eliminating the chance of formation failure and transportation of sand from the reservoir into the annulus and tubing. At first, these reservoirs were produced through depletion, and waterflood of these reservoirs did not commence until reservoir pressures had reached between 5.5–7.0 ppg. This led to differential depletion across these reservoirs, hence increasing the risk of downhole crossflow immediately upon any injection shut down, which may come with sand production resulting injectivity impairment. This has been observed across other wells in the field not fitted with AICD Bypass Valves. The concept of the AICD Bypass Valve is that the device requires a positive injection pressure differential to activate and open and allow fluid to pass through and it will close if the well is shut in due to a drop in the required pressure for valve activation. Since the installation of AICD Bypass Valves, these wells have been shut in multiple times due to platform shutdowns for rig mobilization and each time no drop in injectivity has been observed on restart, and sand production has been observed as predicted. AICD Bypass Valves were installed into two new injection wells in the Nong Yao field, providing a low cost alternative to recompletion or redrill that may be required, if screens become plugged due to sand production triggered by crossflow between reservoirs during well shut-in. This has provided more reliable production for the field and the success in this project means that more AICD Bypass Valves will be planned for future MZC, for injection wells in unconsolidated sand. |
