Predicting the Performance of Gas Boosting Eductors

Abstract

Abstract Eductors, also known as ejectors or jet pumps, are used to boost low pressure (LP) flows by utilizing energy from high pressure (HP) streams. An application can use gas from an HP well to boost production from an LP well. Historically, vendors only provide the performance expectations of an eductor for initial conditions. However, as reservoirs decline, the pressure and flow regimes change making the future performance of an eductor difficult to predict. In this study an eductor simulator was developed, modelling the performance from first principles rather than from generic curves. The development of the simulator tool was based on linking spreadsheets with Integrated Asset Modelling software (IAM). IAM is commonly used for reservoir, well and facility modelling, but does not cover eductors. The eductor itself was modelled in a spreadsheet. The simulator determines the eductor geometry based on the performance curves of user provided initial conditions. Subsequently, a novel nodal analysis method was used to solve the equations governing the motive and suction pressures at the entry and exit of the eductor. For each time step these solutions are transferred to a production simulator to establish pressure and rate decline. The simulator was found to predict eductor performance within ±1% of vendor provided initial time step solutions. As per real eductor performance, the simulator is limited in its capability to handle fluids. In general, the simulation results showed that application of eductors boosts production from LP wells, and increases ultimate recovery from their reservoirs, without impacting the ultimate recovery from the HP source. The simulator was used to predict the performance of two new shallow gas wells boosted by gas from a sidetracked high pressure reservoir, showing an incremental 80 billion cubic feet of gas for an investment corresponding with 10% of the cost of a new well. The simulator is now used to identify eductor related reserves adding opportunities. For the first time engineers are able to simulate the performance of a gas production boosting system, to verify options provided by vendors and to conduct economic feasibility studies with varying eductor geometries and production schedules.