Intensification of fluid removal from flooded gas condensate wells by using gas lift

Abstract

This paper presents the results of a comprehensive study into the patterns of operation of water-flooded gas condensate wells during the final stage of field development. The current state of the oil and gas industry’s resources is characterised by the transition of most large fields into the depletion phase, accompanied by a rapid decline in reservoir energy and the intensive breakthrough of formation water into the bottom holes of production wells. The results of recent domestic and international studies on the causes of well self-shut-in and the negative impact of the accumulation of formation water and hydrocarbon condensate at the wellbore on the hydrodynamic parameters of gas-liquid flow are analysed. The feasibility of converting such wells to gas lift operation is justified as the most effective and flexible method of removing fluid from the wellbore, allowing the required flow velocity at the inlet to the tubing to be artificially maintained and reducing the hydrostatic load on the formation. For the conditions of a hypothetical gas-condensate well, a study was carried out on the combined influence of water and condensate factors on the energy performance of the gas lift system. Using a refined mathematical model for determining the operating parameters of a gas lift pump, quantitative relationships have been established between the required flow rate of the working medium (gas lift gas) and the volume content of water and condensate in the production stream. The research results are presented as a series of graphical relationships between the quantity of gaslift gas and the condensate and water factors within a range of 0 to 250 l/thousand m³. It has been established that the water factor has a decisive influence on the energy consumption of the process: as it increases to its limit values, the required quantity of working agent to ensure fluid removal rises rapidly to 120,000 m³/day. The condensate factor acts as an additional load, the effect of which is most pronounced when formation production has low water cut. It has been demonstrated that, in the simultaneous presence of both liquid components, a cumulative effect of increased mixture density is observed, requiring precise adjustment of gas lift operating modes. The results obtained make it possible to optimise operational parameters, ensure continuous well operation under unstable conditions, and significantly increase well flow rate and the ultimate hydrocarbon recovery factor from depleted reservoirs.