To ICD or Not to ICD? A Techno-economic Analysis of Different Control Strategies Applied to a Thin Oil Rim Field Case

摘要

During end-of-life production from an oil well it is often impossible to sustain continuous production. Gas coning is a common cause of production problems, especially in thin oil reservoirs. This study compares three production strategies that can be used to deal with this problem for a specific field case. The strategies will be evaluated on the basis of two criteria: Total number of barrels produced and Net Present Value (NPV). The three strategies considered are (i) intermittent production, (ii) Well Head Control (WHC), (iii) Inflow Control Devices, (ICD). The first two are currently common practice, while the latter is an emerging technology which is not applied on a large scale yet, because of the larger expense incurred by ICD installation. The onset of gas breakthrough occurs in a much shorter timescale than many other production upsets, such as water flooding, making it a very challenging situation for a control strategy. A coupled dynamic reservoir-well model has been used in order to describe the breakthrough accurately. A simulation environment has been constructed and validated in which different well and reservoir models can be coupled. Since correct prediction of flow and pressure drop over ICDs is essential, special care was taken to accurately model these devices. For the WHC control strategies a Proportional Integral Derivative (PID) algorithm was used. Despite the higher initial completion costs associated with ICDs, they can provide a cost-effective way to reduce long-term operating costs and increase yield. Production targets are achieved with longer, but fewer wells, maintenance and overhead. From a reservoir management point of view, ICDs can improve the productivity index (PI) by maximizing reservoir contact, minimizing gas coning by operating at lower drawdown, and increasing overall efficiency. In this study we evaluate a field case, which suffers from gas coning, to verify whether the implementation and usage of ICDs are cost-effective alternatives, and quantify the relative merits for each technology. The comparison is based on both the total barrels produced and the NPV, taking into account the integral cost, including installation, operating, and maintenance costs.