WELL STABILIZATION USING VELOCITY STRING TECHNOLOGY

This paper investigates the potential for improving the performance of gas-condensate wells in the late stages of field development through the application of Velocity String technology. One of the primary causes of declining productivity in gas and gas-condensate wells is the accumulation of condensate and formation water at the bottomhole due to reservoir pressure depletion and reduced gas velocity within the production tubing. Under such conditions, the gas flow loses the ability to carry the liquid phase to the surface, resulting in increased bottomhole pressure, deterioration of inflow conditions, reduced production rates, and the onset of well liquid loading. The study examines the theoretical principles of Velocity String technology, which involves installing a smaller-diameter tubing string inside the existing production tubing to increase gas flow velocity and ensure continuous liquid removal from the wellbore. To evaluate the effectiveness of this technology, mathematical models of gas inflow to the well, gas–liquid flow equations in the tubing string, J-curves, and the Turner criterion for determining the critical liquid lifting rate were employed. The researchwas conducted using N-well of a gas-condensate field as a case study, utilizing the Cerberus software package and the specialized Velocity Stringmodule. Well performance was modeled for operation through a conventional tubing string with a diameter of 73.02 mm and coiled tubing strings withdiameters of 38.10 mm and 44.45 mm. Forecast values of gas production rate, bottomhole pressure, reservoir drawdown, and critical liquid lifting ratewere obtained. The simulation results demonstrated that the conventional tubing string does not provide stable liquid removal and is associated withliquid accumulation at the bottomhole. It was shown that the implementation of Velocity String technology enables the well to operate in a stable production regime. The most effective option was the use of a 44.45 mm coiled tubing string, which provided the optimal balance between flow velocity, pressure losses, and well productivity. The obtained results confirm the feasibility of applying Velocity String technology to extend the efficient operation of depleted gas-condensate wells and to enhance ultimate hydrocarbon recovery.