Surfactant Effect On Tight Reservoir Oil Recovery Through Imbibition

The tight reservoirs in Ordos Basin are rich in oil and gas resources,and the exploration and development potential is great,but the conventional waterflooding effect is poor.Some studies have shown that surfactant has an obvious effect on enhancing the ability of self-imbibition and oil recovery of tight reservoirs,and is one of the potential methods to increase the waterflood recovery of these reservoirs.The permeability of Chang 8 tight sandstone reservoir in HQ area of Ordos Basin is less than 0.3md,and the reservoir rock is mainly fine-medium sandstone with high content of crevices,generally more than 10%.The pore structure of reservoir rock is complex.Based on the analysis of petrology and pore structure of Chang 8 reservoir in HQ area of Ordos Basin,this paper selects and appraises the possible formulation of surfactant,and through the experiments of self-imbibition and nuclear magnetic resonance(NMR)in the core,The influence of formulation type of surfactant on the core self-imbibition process and the self-imbibition recovery of reservoir is studied.Based on this,the application method and prospect of this technology in the research area are discussed.The results show that:(1)Surfactant can increase the water absorption capacity of reservoir rock and make the flow of oil easy by changing the wettability and oil-water interfacial tension.(2)For the reservoir in the study area,the three formulas selected were significantly higher than the self-imbibition ability of formation water;the best formulation is the combination of anion and non-ion.(3)No.2 formula has the lowest interfacial tension and relatively good self-imbibition.The auto absorbent recovery ratio can reach 37%-64%.(4)NMR experiments show that the water can enter into smaller micropores,and the self-imbibition capacity of core is increased in the study area.(5)In the study area,the oil recovery can be increased by the way of surfactant huff and puff.(6)The results of this paper provide a basis for screening and enhancing oil recovery in the research area.