Mass Transfer between Matrix and Fracture during EOR Application

The application of enhanced oil recovery techniques in naturally fractured reservoirs somewhat differs from conventional reservoirs. It is well-known that after the injection of tertiary recovery materials into the naturally fractured reservoirs, oil-saturated matrix blocks are left unswept while the fracture network is saturated with injected fluid. Therefore, for an efficient recovery of oil from naturally fractured reservoirs, the mass transfer between matrix and fracture must be maximized. Generally, the mass transfer between matrix and fracture is conducted as a result of four factors: pressure, gravity, dispersion/diffusion, and capillary drive. In this study, the results of previously conducted experimental and numerical simulations are reviewed to evaluate the contribution of different pre-mentioned factors on mass transfer between matrix and fracture. Experimental studies have been performed by using both ۳D core and ۲D glass models. By putting the results of experimental and simulation studies together, the dominancy of gravity drive is observed, which leads to a “buoyant conductive” front. By neglecting the effect of gravity through using horizontally oriented condition, it is observed that the displacement front is transferred to “bullet-shaped” as a result of diffusion/dispersion drive. Investigation of the other effective parameters on mass transfer between matrix and fracture illustrated that the convective and diffusion/dispersion mainly depends on oil viscosity (not density) and rock properties (porosity and permeability), respectively. Additionally, it is observed that the ultimate recovery increases at later times for the case of a lower injection rate, however, the recovery is higher at the initial stage for the case of a high injection rate. This observation indicated that the initial phase of the recovery curves is dominated by displacement or viscous forces and the diffusion comes into picture at a later stage.

کلیدواژه ها:

Mass Transfer ، Matrix-Fracture Interaction ، Naturally Fractured Reservoirs (NFR) ، Capillary Drive ، Enhanced Oil Recovery (EOR)