According to microcosmic porous and throats model’s experiment which will be performed in Kexia layer, Qizhong district of conglomerate reservoir in Xinjiang oil fields, microscopic displacement mechanism of surfactant/polymer flooding was researched. Surfactant/polymer flooding has a significant effect on enhancing oil recovery because of the effect from the polymer’s viscosity and the surfactant’s interfacial tension. According to microcosmic porous and throats model’s experiment, the best polymer viscosity and surfactant interfacial tension were determined.
In China, most of undeveloped oil reserves are low and ultra low permeability reservoirs. The total remaining petroleum reserves of CNPC is about 4.07×107m3, and the low and ultra low permeability reserves is 3.16×107m3, So it is important to reasonable develop the oil reserves to keep the petroleum output stable. Under the low permeability layer condition, it is difficult to inject water to the formation, and the output of oil well is very low. The chemical agent can solve the difficulty of injection water and enhance the oil recovery. The relative permeability experiments shows irreducible oil was reduced by the wettability alteration agents, and the mobile oil saturation increased, which enlarging the range of the two phases co-flowing and enhancing oil recovery. As a result with alteration agents, the cross-point relative permeability moves to right, and the core converts to water-wet. In daqing oil field test, the water injection pressure is reduced by 15%, and the term of validity is more than 10 months.
Because plenty of polymers have been added in the surfactant/polymer (S/P) flooding fluid, its viscosity becomes higher. So when S/P flooding fluid flows in the stratum, its threshold pressure gradient is an important influence factor. According to study S/P flooding fluid with different viscosities that flows in different permeability cores, the variation laws of seepage curve have been obtained. The results of the study show that the seepage of S/P flooding exhibits nonlinear seepage in low velocity, and changes gradually to linear flow as the pressure gradient rises. As well, S/P flooding has obvious threshold pressure gradient when its speed is low. The threshold pressure gradient of S/P is related to the permeability of the core and its own viscosity. The higher the viscosity, the lower the permeability of the core, the threshold pressure gradient will be greater.
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