MACROSCOPIC AND MICROSCOPIC INVESTIGATION OF ALKALINE-SURFACTANT-POLYMER FLOODING IN HEAVY OIL RECOVERY USING FIVE-SPOT MICROMODELS: THE EFFECT OF SHALE GEOMETRY AND CONNATE WATER SATURATION

摘要

Plenty of oil reservoirs contain discontinuous shale layers that act as flow barriers. Therefore, understanding their influences on reservoir performance, especially during enhanced oil recovery (EOR) processes, is of great importance. For this purpose, several experiments of water and alkaline-surfactant-polymer (ASP) flooding have been performed on a number of one-quarter five-spot micromodels that contain various configurations of shale layers to simulate shaly porous media. Several features, such as various shale geometrical characteristics and the presence of connate water saturation, were investigated at both macro- and micro-scales. The presence of shales resulted in earlier breakthrough and lower recovery factor due to oil trapping in comparison with the homogenous model (the model with zero shale content). Also, the results illustrate an increase in oil recovery factor with increasing shale orientation (shale angle with mean flow direction), length, distance to producing well, and continuity. On the contrary, increasing shale density (number of shales) and spacing between them caused reduction in oil recovery factor. The effects of connate water saturation on displacement and sweep efficiencies of ASP flooding were also investigated. Several important phenomena relating to the connate water presence were perceived at micro- and macro-scales through analysis of microscopic images in addition to macroscopic examination of the experiments. This study demonstrated the ability of glass micromodel experiments in surveying EOR processes, especially ASP flooding in shaly heavy oil reservoirs, and also visualization of dominated mechanisms occurring at pore scale.