Experimental and Simulation Studies of the Effect of Vertical Permeability Barriers on Oil Recovery Efficiency During Solvent Injection Processes

Abstract

Almost all of the heavy oil reservoirs contain discontinuous permeability barriers (shales) with different structures. However, the effect of shaly layer geometrical characteristics including: spacing from wells, discontinuity, orientation, shaly layers' spacing and length, and heterogeneous distribution on oil recovery factor in the presence of gravity force are not well understood. In this work, a series of solvent injection experiments were conducted on various vertical one-quarter five-spot glass micromodels, containing barriers, which were initially saturated with a heavy oil sample. The oil recovery was measured by analysis of the pictures provided continuously during the injection processes. The experimental data were used for developing and validating a compositional-numerical model. The results indicated that the ultimate oil recovery in the presence of shales is lower than that in homogeneous models. The gravity force caused the solvent to be propagated better in the media. It was observed that the oil recovery is inversely proportional to the shaly structure's orientation with the main flow direction; by increasing the length of the shaly layers in the flow direction, the sweep efficiency decreased. However, with constant length, it was observed that the shaly layers' discontinuity results in higher oil recovery. The lower distance of these barriers from the production well reduced the final oil recovery, but it acted conversely for the case of the injection well. By increasing either the horizontal or vertical spacing between barriers or reducing the percent of the heterogeneously distributed shales, the recovery value improved.