Comparison of streamline-based and grid-based dual porosity simulation

In field-scale dual porosity models, fractured reservoirs are represented as two intercommunicating domains: a flowing fraction composed of the connected fracture network and high permeability matrix; and a stagnant fraction composed of lower permeability matrix containing most of the original oil. The transfer of fluids between fracture and matrix is modeled by an empirical function of saturation. Two transfer functions are used in a streamline-based dual porosity code: (1) a conventional transfer function used in traditional grid-based simulators; and (2) a new linear transfer function that reproduces the results of core-scale imbibition experiments. The results of the simulations are compared with those from a conventional grid-based finite difference code. The two codes give very similar results, but the streamline code requires a much shorter run time and has a lower memory requirement. Using the linear transfer function, the streamline-based code is orders of magnitude faster and requires many times less memory than the conventional grid-based code. The larger the number of grid blocks, the greater the relative speed of the streamline-based approach. It is possible to run a 4.5 million grid block dual porosity model on a standard PC using a streamline code.