This paper presents the methodology, implementation, and results of the dynamic modeling of a naturally fractured carbonate reservoir, which consists of a fracture swarm system and high matrix permeability. The focus of this paper is on the description of the dynamic single-media model that was used to history match the production. The challenges in properly quantifying the separate effects of matrix and fracture within the framework of a singlemedia model become the major objective of the study. A brief description of the static model (which consists of the development of matrix and fracture models, as well as the method to integrate them) is also presented.
Both matrix and fracture systems play an important role in the production mechanism of the reservoir. History matching for 20 years of production was done successfully in a single-media model through an iterative process between static and dynamic models to ensure the consistency between the two models. Different sets of relative permeability curves (for matrix and fracture systems) were generated to properly simulate the fluid movement in the reservoir.
The results indicate an excellent history match that is also followed by the success in the blind tests of newly drilled wells. Significant improvement was obtained compared to the previous model in simulating water production that comes from the aquifer to the wells through a complex fracture network. The results were achieved through various sensitivity analyses of fracture conductivity and by fine-tuning relative permeability curves that are based on the eight rock types defined for the reservoir.
In conclusion, the single-media model used in this study can successfully simulate the behavior of a naturally fractured reservoir. The model has shown that it can produce excellent results in a very practical way.
The methodology described in this paper is suitable for other naturally fractured reservoirs, especially in the Middle East area, where a significant difference between core-derived permeability and well-test-derived permeability exists.