Abstract
Due to the coexistence of multiple types of reservoir bodies and widely distributed aquifer support in karst carbonate reservoirs, it remains a great challenge to understand the reservoir flow dynamics based on traditional capacitance–resistance (CRM) models and Darcy’s percolation theory. To solve this issue, an improved injector–producer-pair-based CRM model coupling the effect of active aquifer support was first developed and combined with the newly-developed Stochastic Simplex Approximate Gradient (StoSAG) optimization algorithm for accurate inter-well connectivity estimation in a waterflood operation. The improved CRM–StoSAG workflow was further applied for real-time production optimization to find the optimal water injection rate at each control step by maximizing the net present value of production. The case study conducted for a typical karst reservoir indicated that the proposed workflow can provide good insight into complex multi-phase flow behaviors in karst carbonate reservoirs. Low connectivity coefficient and time delay constant most likely refer to active aquifer support through a high-permeable flow channel. Moreover, the injector–producer pair may be interconnected by complex fissure zones when both the connectivity coefficient and time delay constant are relatively large.
Highlights
The hydrocarbon resources stored in carbonate reservoirs play an important role in new proven reserves worldwide over the last decade
When the improved CRM–Koval model was used for a better understanding of reservoir fluid dynamics including inter-well connectivity, aquifer influx rate, etc., the net present value (NPV) of production was defined as the objective function by having the proxy model serve as a precursor of a grid-based reservoir model and maximized in order to find the optimal well controls under hybrid non-linear constraints, which can be given as follows [22]
We develop an improved CRMIP model by coupling the effect of active aquifer support and CRMIP model byoptimization coupling thealgorithm effect of active aquiferevaluation support and integrated it with an theimproved newly developed for accurate of integrated it with the newly developed optimization algorithm for accurate evaluation of reservoir dynamic connectivity in a waterflood operation
Summary
The hydrocarbon resources stored in carbonate reservoirs play an important role in new proven reserves worldwide over the last decade. We will explore the possibility of using StoSAG for the case where two objectives are to assimilate the production history data to infer inter-well connectivity when active aquifer support exists and to perform real-time production optimization by maximizing the NPV or cumulative oil production under hybrid non-linear constraints, respectively. An improved CRMIP model by coupling the effect of active aquifer support is first proposed and integrated with the newly developed StoSAG optimization algorithm for better understanding of inter-well connectivity in a waterflood operation. The improved CRM–StoSAG workflow is further employed for real-time production optimization to find the optimal injection rate at each control step by maximizing the objective function, i.e., net present value (NPV) of waterfloods with regard to typical karst carbonate reservoirs.
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