Different Equivalent Simulation Methods for Fractured-Vuggy Carbonate Gas Condensate Reservoirs

Abstract Multi-scale pores, fractures, vugs and caves are developed in the naturally fractured-vuggy carbonate gas condensate reservoirs in China. How to properly forecast the performance of this kind of reservoirs based on reservoir simulation is a major challenge. This paper documents some of the key elements involved in construction of a representative and equivalent numerical model for this kind of reservoirs. Base on the characteristic of fractured-vuggy gas condensate reservoirs in China, different kind of reservoir patterns are identified. And three equivalent simulation methods are proposed in order to characterize the complex vug-fracture-cave architecture. Take T1 fractured-vuggy carbonate gas condensate reservoir in China for example. The deterministic modeling and simulation method is used for large cave pattern reservoir. While for the other kinds of reservoirs, different simulation models include fine single porosity model, dual porosity model with different modeling method. And the different models are all built in both structured and unstructured grid, among which the single porosity fine unstructured grid model is considered as the correct solution. But simulation time of the fine single porosity model is too long to use for the practical full filed simulation. While it brings certain errors if the other models used compared to the fine single porosity model, and dual porosity model with structured gridding are selected as the equivalent simulation method. Then through matching the simulation results of fine single porosity model, the pseudo-relative-permeability curve, the pseudo-capillary-pressure curve and the composition transport coefficients are established for the dual porosity model. Finally, the generated pseudo-curves are applied for the equivalent simulation of full field T1 reservoir. This equivalent simulation method has been successfully applied to T1 carbonate gas condensate reservoir, which are verified by the actual reservoir performance. It also provide a method for reservoir development strategy optimization, which are also used in T1 optimization development plan later.