Studies On Enhancing Oil Recovery Technology Of Polymer/surfactant Binary Flooding

Basing on Experimental research, a comprehensive analysis of the main factors affecting oil displacement efficiency of binary flooding was carried out, and some suggestions for pilot test was given.As for reservoir conditions of Qizhong area in Karamay Oilfield, polymer/surfactant binary system formulations for this block was proposed, further in combination with Polymer injection-site situation in Qidong area and by studying the physical and chemical properties and injection ability (resistance coefficient and residual resistance coefficient) of polymer, the polymer used for binary polymer flooding in this very block was recommended.The interfacial tension, viscosity enhancing ability, oil displacement efficiency, long-term stability, adsorption stability, improving mobility abilities of the binary system were studied, and the interaction between polymer and surfactant was analyzed. The binary system formulations with Interfacial tension in the range of 100～10-3 of were determined, and surfactants for different formulations were optimized.By core experiments, that viscosity ratio between binary systems and oil of Qizhong area is greater than 2.0 was determined, and the optical interfacial tension is 10-3mN/m, the binary flooding systems can enhance oil recovery by 24.24% at the utmost.Polymer/surfactant binary Flooding microscopic mechanisms include: denudating and emulsifying oil film, starting blind-end residual oil, carrying emulsion, drawing and moving oil droplets, cutting oil droplets, oil droplets shifting along the wall and starting residual oil in the channel and so on. Compared with the polymer flooding, the ability to start more residual oil of binary flooding is greater.Compared with the ternary flooding, given that the ability to start residual oil of binary flooding is weak, appropriate amount of alkaline can be added in the early stage of injection to enhance the ability of starting residual oil to reach the goal of reducing the negative effects of alkali, but also to maximize the enhancing oil recovery of binary flooding.Viscosity ratio between binary systems and oil in Micro-pore model needs to be above 1.0. Viscoelasticity of polymer flooding plays a great role, as the viscosity ratio increases, the flexibility contribution rate increases; with the interfacial tension reduction, recovery was significantly increased. To displace residual oil in the pores, ultra-low interfacial tension is necessary.In binary flooding process, low capillary number makes that the function points are more dispersed while high capillary number makes that the function points are more concentrated. Relative permeability is the dual function of saturation and capillary number, in the same saturation value, the relative permeability increases with increasing capillary number, and the even larger increase with oil, making oil fractional flow increased. The basis of that Relative permeability is the dual function of saturation and capillary number was proposed, and two-phase flow equation considering changes in the capillary number was established:Buckley-Leveert two-phase flow theory was extended, which will obtain some new concepts and new phenomenon when it is applied to porous flow mechanism of chemical flooding.