Waterflood Management Using Streamline-Based Inter-Well Flux Information and Classical Finite Volume Reservoir Simulation

Abstract In this work, we implement new software for improved waterflood management by combining classical finite volume reservoir simulation together with streamline tracing and corresponding inter- well flux evaluations to optimize waterflood performance. We show reduced water cut and improved oil recovery by using streamline-based flux information to adjust well rates, while retaining the advantages of rigorous finite volume simulation. We have introduced two basic modules here: a commercial reservoir simulator Eclipse and our own streamline tracing and waterflood management program. Waterflood simulation is performed for a certain time span until simulation is paused and the streamline tracing program is called to calculate inter-well fluxes and adjust new well rates for better waterflood performance. The simulation continues afterwards until the next tracing and adjustment point is reached. The two modules work iteratively. The streamline tracing program uses the classical Pollock's tracing method. It is designed to trace streamlines on a compressible velocity field and a general corner point grid system with non- neighboring connections. The new injection rates are adjusted according to each well's injection efficiency calculated from inter-well fluxes as proposed in previous works. Our waterflood management program successfully works cooperatively with the commercial simulator, with data transfer realized by making the simulator to output the velocity field and other information into restart files. Streamline tracing is performed successfully not only on simple geometry corner point grid cases, but also on heavily-faulted realistic reservoirs under waterflood. Streamline- based inter-well multi-phase fluxes are calculated, in which the injection efficiencies are derived accordingly. Injectors with higher efficiencies will receive more water from the source, according to the injection allocation algorithms and vice versa. After re-adjusting injection rates multiple times during the simulation, we typically observe a reduction in field water cut of up to 5% and an increase in oil recovery in our test cases. Inter-well flux information serves as effective diagnostic tools to identify injector-producer pairs with large amount of water cycling. All simulations conducted here are rigorously finite volume based, which takes into account the full physics of non-advective processes such as gravity and capillary effects. In conclusion, we have implemented a streamline-based waterflood management program which works iteratively and cooperatively with a commercial reservoir simulator, without switching to streamline simulation. It provides an effective solution for improving oil recovery in brown fields by combining the rigorous mathematical nature of finite volume simulation and the power of streamline- based flood management.