Compositional Modeling of Molecular Diffusion in Natural Gas Injection of Tight Gas Fractured Reservoirs – Single Block Approach

Regarding of molecular diffusion drive simultaneously with the pressure gradient drive in the porous media usually refers as multi-mechanistic flow in the reservoir. A multi-mechanistic flow environment is the result of the combined action of a Darcian flow component and a Fickian-like or diffuse flow component taking place in hydrocarbon reservoir. In this work, single block approach applied to find out main mechanisms of recovery from a gas fractured reservoir. In order to review all aspects of the exact influence of molecular diffusion phenomena; first of all we startwith a very simple problem and gradually we begin to complicate the issues until we reach a case very similar to the real reservoir. Fully implicit with the using of Newton-Raphson technique was applied to solve highly non-linear equations at this simulation model. In order to speed up the simulation technique, Broyden updating approach is used to build jacobian matrix. At the end, it will be concluded that the diffusion phenomenon is considerable for matrix blockswith the permeability of lower than 0.01 md. For matrix blocks with the permeability of lower than 0.0001 md in spite of applying high pressure drawdown and neglecting diffusion no recovery predicted by simulator.