Pore-Level Study of Viscous Forces during Immiscible Gas Injection in a Fractured Multi-Block System

One of the most applicable methods for enhancing the matrix-block oil recovery in gas invaded zone of fractured reservoirs is the use of viscous forces during gas injection/recycling. It has been known that in this zone the capillary has a resistant role while the gravity acts as a driving force. However the effect of viscous forces on the matrix-fracture interaction during gas injection is not well understood. In this work a new design of glass micromodel, which includes two classes of matrix-blocks open and close to flow, was constructed as a multi-block system. Experiments were performed on this system at several fixed injection rates based on a novel derived capillary number. The model flooded by nitrogen was initially saturated with kerosene. Experimental results revealed that for each class of matrix blocks, there is an optimum rate of gas injection which gives the maximum ultimate recovery with a minimum flooding time and pore volume of injected gas. Also pore-level observations showed that at high injection rates, an invasion percolation behavior was developed in the matrix-blocks, which causes oil trapping and a fractal pattern gas-oil displacement. However at low injection rates, there is a diffusion-limit behavior through the matrix which results in no oil trapping and a branched structure displacement. The results ofthis work can be helpful for better understanding of the viscous force mechanisms during gas injection in the gas invaded zone of fractured reservoirs.

کلیدواژه ها:

Pore Level ، Viscous Force ، Fractured Porous Medium ، Multi-Block ، Gas Injection