Waterflood management for naturally fractured reservoirs is a difficult task due to complex fluid behaviors between fracture and matrix.The streamline model is particularly useful for assessing the individual contribution of injectors to each producer accounting for inter-porosity transfer.A simulation model for naturally fractured reservoirs was developed aiming at improved waterflood management with the use of the concept of streamline-derived injection efficiency(IE).Waterflooding in the dual-porosity dual-permeability system is first modeled by the streamline approach employing the operator splitting technique to account for gravity and transfer between fracture and matrix.IEs for individual injector-producer pairs are determined from saturation profiles on streamlines in both continua after evaluating transfer effects.The model is capable of performing the reallocation of injection water to improve oil recovery from fracture and matrix.The model can also be applied readily to field-scale simulation because of rapid calculations with the streamline method.This paper describes the methodology and implementation of IE-based injection-rate control for dual-porosity dual-permeability reservoirs and demonstrates the applicability by simulation examples.Application of the method makes it possible to evaluate the dynamic efficiency of the injected water for individual injector-producer pairs.Based on the computed IEs,reallocation of the injection rate among the injectors is made so that more oil in matrix and fracture is displaced by injected water.The examples showed usefulness of the method for naturally fractured reservoirs of highly heterogeneous matrix and fracture properties.
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