Gas Lift Robbing Prevention in Dual String Completion using Production Pressure Operating Valve

Abstract

Common problem for dual string completion gas lift well is a misallocation problem called as a gas lift robbing, where the gas tends to be injected uncontrollably to one of the tubings. Consequently, both oil production of the strings drops since the injected gas does not meet the optimum allocation. To solve this, engineers need to shut in one of the strings using wireline which is time-consuming and uneconomic. Therefore, the objective of this paper is to introduce the modification of dual string gas lift design that can economically prevent gas lift robbing problem in the well during the production time. This finding occurred in Indonesia, Offshore North West Java field, where the orifice is preferably used as the operating valve. However, Production Pressure Operating (PPO) valve is then used to replace the orifice function to overcome the problem. The methodology starts with well selection based on the possibility to perform the new design. Then, the static bottom-hole pressure test applied in each zone to obtain an appropriate pressure. Lastly, PPO valve’s Pressure Test Rack Opening (PTRO) will be designed based on the measured bottom-hole pressure to be applied to one of the selected string to prevent the gas lift robbing. The force balance is then calculated, and the PPO valve is set to the short string with the Pressure Test Rack Opening (PTRO) 585 psig at 80°F. The oil production in the robbing well observed to increase by 45% and achieved a sustainable production after replacing its orifice with the PPO valve. Also, The PPO valve will prevent the gas robs to the selected string as it will close automatically when its tubing pressure drops bellow PTRO. Hence, the wireline activity is now unnecessary because the PPO valve will be closed automatically when the gas lift robbing occurs again. The use of PPO valve is commonly suitable as an unloader in low availability of Casing Head Pressure (CHP) and high reservoir pressure. By this study, PPO valve has been successfully replaced orifice function with high CHP and low reservoir pressure to prevent the gas lift robbing problem effectively in Offshore North West Java field.