Experimental Study Of Oil Recovery Mechanisms By Air-foam Injection Using Micro Models

In recent years, many main units in our country have entered high water-cut stage. A large part of oil layers is difficult to be spread due to the effect of reservoir heterogeneity, so the technologies of gas injection and foam injection have attracted wide attention.Foam flooding with a high efficiency, some characteristics in the nature of foam flow superior to plugging back high capacity channel and water flow channel. The technology of air-foam injection take full advantage of cheap air and air-foam's effective blocking, which help to further improve oil recovery. Currently, the technology of air-foam injection has already been applied repeatedly in many oil fields, and it has been proved that air-foam injection can improve oil recovery by 10%~25% after water flooding. In this paper, visualization of micro-porous media models combined with foam performance evaluation instruments and the core displacement tests, are conducted to analyze the mechanisms of air-foam injection and seepage characteristics.We take advantage of reformed Ross miles foam equipments to select foaming agents and evaluate the foam ability, study and analyze the foam ability of different foam agent in different working conditions.The results indicate that temperature, foam agent concentration, formation salinity and oil saturation have impact badly on the foam performance. From the experiment we can achieve that the foam comprehensive performance show a general downward trend by temperature, oil saturation, and select the best foam agent ZY-1.Light-eroded micro simulation glass models were used to simulate the air-foam injection process in porous media, the pictures of injection process were collected, and the infiltrating fluid characteristics and injection process of air-foam in the pore were analyzed .In the mean time, the generation, migration, breakdown, and regeneration process were observed and analyzed. The results indicate that air-foam not only blocks the channel of high permeability which can achieve the same velocity in the plane heterogeneous model, but also appear the phenomenon of the gravitational differentiation in the vertical. Microscopic mechanisms of foam flooding are mainly reflected in not only expanded the micro-swept volume but also improve the micro-extraction efficiency.Many foam blank-off ability evaluation tests have been done by sand-pack tube models, from which we can conclude that foam blank-off ability decrease with the temperature increasing, and the foam with strong overall performance has the better blank-off ability. The results of sand-pack tube models tests validate and match well with previous experimental results.