On the physics of multimechanistic gas-water flow in fractured reservoirs

Multimechanistic flow occurs in reservoirs when the fluid transport is influenced by both, pressure and concentration gradients. In this research, we investigate the dynamics of multi-mechanistic gas-water transport in fractured systems. To achieve this objective, we have developed a two-phase, two-dimensional dual-porosity, dual-permeability simulator. The details of the simulator development are presented in a previous paper (Chawathe et al., 1996). Our studies indicate the presence of higher flowrates and cumulative production at early times in systems experiencing multimechanistic flow. This is attributed to the higher draw-downs experienced by such systems. At late times, a 'choking effect' is hypothesized to be responsible for higher cumulative production. In this paper, we investigate the physics underlying this multimechanistic flow behavior. We do this by carefully analyzing a fractured system which clearly displays multi-mechanistic flow characteristics.