EXPERIMENTAL STUDY ON WATER INJECTION HUFF AND PUFF OF LOW PERMEABILITY FRACTURED SANDSTONE RESERVOIRS

In order to improve the oil recovery of fractured low permeability reservoirs, the feldspathic sandstones of a low permeability fractured reservoir in western China were studied. The cores with different wettability values were simulated under formation conditions (22MPa, 83 degrees C) to study the dynamic behavior of the initial stage and the elastic mining stage. The research on the mechanism of Water injection huff and puff and oil recovery based on factors such as capillary force, permeability and throughput cycle were carried out. According to the comprehensive analysis, (1) the recovery rate increased by 4.3,4)similar to 15.23% under the action of water injection; (2) water injection can have effects on various wet state reservoirs, the stronger the hydrophilicity, the higher the recovery degree; (3) Capillary force exerts displacement and sorption on cracks and matrix system. The pressure deflection effect formed between the high and low permeability layers affects the oil-water interaction process between the heterogeneous oil layers, improves the sweep coefficient and the oil displacement efficiency, and reduces the remaining oil.