Experimental investigation on block and transport characteristics of foam in porous media for enhanced oil recovery processes

Foam microscopic block characteristics were investigated in a 2D-visualization flow test and big 3D core foam flooding experiment. The foam macroscopic block characteristics and transport mechanism in porous media are investigated by measuring the production performance and pressure distribution in a positive rhythm heterogeneous reservoir model. Blockage of the throat by bubbles happens with single large bubble blocking or small bubble bridging and composite plugging with multiple bubbles. The distribution of the high-pressure gradient zone at a different time reflects the transport characteristic of the foam front and the oil bank formed during foam flooding. The selective blocking feature can effectively increase flow resistance and pressure, and promote the flow direction from the high permeability layer to the middle and low permeability layer, resulting in the expansion of swept volume. When 0.8 PV foam with the quality of 66.7% is injected into the big 3D core in the tertiary model, an incremental oil recovery of 21.19% OOIP is observed. The inlet pressure rises sharply from 40 kPa at waterflooding to 156.60kPa after foaming flooding, increasing approximately by 4 times. Foam can not only improve the displacement efficiency in the high permeability layers but also improve the displacement and expanding efficiency in the mid and low permeability layers. After the foam flooding, the incremental oil recovery rate in the high, media and low permeability layer is about 18.33%, 20.03%, and 23.23% OOIP respectively, indicating the influence of heterogeneity and effectiveness of foaming flooding. The primary way to enhance oil recovery in heterogeneous reservoirs is to increase oil displacement efficiency based on expanding the sweeping volume. In addition, the results of 3D foam EOR experiment provide an experimental basis for numerical simulation and play an important role in understanding and the application of the foam-EOR method in the heterogeneous reservoirs.