Waterflood Optimization using Streamline Simulation
Waterflooding is a secondary recovery process in which water compatible with the reservoir of interest is injected into the reservoir to displace residual oil. The goal of waterflood management is to maximize oil recovery and economics from a given waterflood project while minimizing injection water volumes and the effects of reservoir heterogeneities. This research focuses on the application of streamline simulation to optimize a waterflood. The streamline-based simulation workflow proposed by Thiele et al (2006) is used for computing well allocation factors (WAFs) and injection efficiencies. The WAFs and injection efficiencies are used to optimize oil recovery by effectively reallocating injection water. Proposed methodology is validated with a case study to demonstrate pattern balancing as a flood management tool by reallocating available injection water to more efficient injection wells in a 5-spot pattern waterflood, thereby optimizing oil production for each barrel of water injected. Several factors that will impact the performance of waterflooding were analysed. These factors include the time to start injection water reallocation, duration of reallocation cycles, zones of injection, kV/kH ratios and formation heterogeneity. Dysktra-Parsons Coefficient (VDP) was used as a measure of heterogeneity. Water flood optimization was evaluated by analysing the trends of field average reservoir pressure, cumulative oil production and field water-cut over time for several scenarios of the waterflood. The trends were compared to a base case – waterflooding without optimization. The results show that zones of injection play a significant role in the performance of waterflooding. It was also observed that kV/kH ratio and heterogeneity have significant impacts on waterflood performance. The results show that injection water reallocation should be started early in the life of the waterflood project. Data from the case study indicated that a 12-month duration of reallocation cycles is the optimum duration for reallocating injection water to maximize oil recovery. The simulations show that for effective water flood management there is need to consider both field injection rate and well injection rate constraints. The results of this study can be applied to all waterflood projects, especially mature waterfloods to improve oil recovery and reduce field and well water-cut.