Feasibility Research Of New Oil-Displacing Surfactant System In Mid-Low Permeability Oil Layers

Nowadays, the water drive recovery efficiency factor in low permeability reservoirs is low, in order to solve this puzzle, this paper did some experimental researches, which used the ultra low interfacial tension oil displacing system formed by BS13 betaine surfactants and low molecular weight polymer. Those experimental researches of physical simulate oil displacement include artificial cores oil displacement experiment, microcosmic simulation model oil displacement experiment and crude cores oil displacement experiment. Artificial cores oil displacement experiment includes isotropic and anisotropic artificial cores experiment. The result of artificial cores experiment indicated: The effect of general activated water drive is not well, the general activated water drive recovery efficiency factor in isotropic artificial cores is 2.42% and in anisotropic artificial cores is 3.41 %. Infuse activated water reduced injection pressure in a certain extent, and different time of infusing activated water segment into isotropic cores has big effect to total oil recovery efficiency factor. Compared with general activated water displacement, the oil recovery efficiency factor of infuse activated water segment earlier is higher, and cumulative infuse pore volume multiple is less, but it make no difference for anisotropic cores. Under the same injecting conditions, the enhanced recovery efficiency factor of injecting compound segment(BS13,0.1%+polymer, 400mg/L) is 3.52% higher than that of only injecting pure BS13 (0.1%) activated water segment. For isotropic cores, the enhanced recovery efficiency factor of injecting two segments of polymer(400 mg/L) and BS13 (0.1%) activated water is 2.44% higher than that only injecting compound segment(BS13,0.1%+polymer, 400mg/L), but for anisotropic cores, the enhanced recovery efficiency factor is very closed. The size of compound segment has some influence to oil recovery, the enhanced recovery of 0.3 injecting pore volume multiple is higher than that of 0.2 injecting pore volume multiple. The result of microcosmic simulation model oil displacement experiment indicated: The single BS13 activated water has strong wash efficiency, but macro affect scope can't extend in inject process, the effect is not well. Infuse activated water and polymer compound segment can improve water-oil fluidity ratio, startup remained oil that water drive can't affected, and the effect of replacement is better than single activated water drive. The result of crude cores experiment indicated: In the same experiment scheme of artificial cores and crude cores, the displacement effect and rule are the same. Considering the influence of infuse rate in low permeability oil layers, inject fluid and fluidity ratio of crude oil, I had amended sutra capillary numeral and finally confirmed the sutra capillary numeral amend formula of low interfacial tension system drive oil in low permeability oil layers after water drive.