Heavy oil reservoirs are known for their low recovery factors. Additional energy consumption, special operations, and enhanced oil recovery (EOR) techniques are required for production due to high viscosities. Also, unfavorable water-oil mobility ratio is a serious problem when waterflooding (WF) is implemented, usually causing early breakthrough and higher water cut. Developing and managing a production strategy through a comprehensive decision-making procedure is also complex due to the high number of variables, uncertainties, and physical phenomena involved. Polymer flooding (PF) is an EOR method that can be applied to heavy oil reservoirs to improve field performance by producing more oil and reducing water production. This improvement is achieved through the increase in water viscosity caused by the injection of polymers, thus reducing water-oil mobility ratio, and obtaining better oil displacement efficiency. In the case of intelligent wells (IW) equipped with Inflow Control Valves (ICVs), the WF limitations can be mitigated by controlling multiple production/injection zones, increasing oil production, and maintaining the reservoir pressure. This work aims to perform a nominal production strategy optimization to develop and manage a heavy oil reservoir considering PF as a production strategy (using conventional wells only) and comparing it to waterflooding with ICVs (WF+ICV) for the same case. A complete methodology to optimize the design and control variables is applied to the strategies by using model-based reservoir simulation. The objective function (OF) is the Net Present Value (NPV), this study case is named EPIC001, which has a 13° API heavy oil reservoir that represents part of a Brazilian offshore field. We have applied a specific methodology to optimize the PF strategy for a heavy oil reservoir of a nominal case which is practical and clear in the selection and comparison of strategies for similar cases. The results found PF strategy is the more suitable for the case, obtaining an NPV that is 21% higher than WF+ICV. Injecting polymers in the earlier stages of the life cycle at lower polymer concentration rendered PF with greater oil recovery (+13%) with a better efficiency in management of water and polymers, therefore surpassing the good ICV management from WF+ICV.
Tag: ICV
Methodology to optimize the WAG-CO2 injection strategy and injection well ICV control rules in light-oil carbonate reservoirs with pre-salt features
Reservoirs of the pre-salt contain a significate amount of CO2 that should not be emitted into the atmosphere. The WAG-CO2 injection process is an alternative to give an ecologically sustainable destination to the CO2 and can increase oil recovery in the pre-salt fields. The optimization of the WAG-CO2 injection scheme, such as cycle duration, can significantly affect its performance in terms of oil recovery and net present value (NPV), raising the need for good optimization methods. In the face of the high uncertainty that typically exists in these scenarios, Inflow Control Valves (ICV) provide operational flexibility to the production strategy, allowing to manage field injection/production more efficiently. This work proposes a methodology to optimize the injection well control variables since the early stages of field development that considers the condition of total gas reinjection (CO2 and natural gas). The methodology optimizes the
opening phase that each well will start injecting during the ramp-up period of the platform, the cycle duration and the phase, gas or water, that each well will inject in the first WAG-CO 2 bank, and the injection wells ICV control rules. The developed methodology was applied to a benchmark case called UNISIM-II-D, based on Brazilian pre-salt trends. Compared to a based injection strategy, the methodology proved capable of improving field management at minimum added cost, increasing oil recovery and the net present value.