Experimental Study Of Surfactant Flooding System For Low Permeability Reservoirs In Zhongyuan Oilfield

According to the conditions of low waterflooding recovery efficiency of low permeability reservoirs in Zhongyuan Oilfield, in order to screen surfactant flooding system available to W92 northern reservoir, experiments of seven Nonionic-Anionic surfactant flooding systems which could lead to ultra-low interfacial tension with the oil of W92 northern reservoir were carried out in the lab without alkali. In this paper, we have examined interfacial tension and compatibility of seven surfactant flooding systems to screen the best formula, and optimized the concentration of three Surfactant Flooding Systems (SHPC3, SHPC4 and SHPC7) with superior performance. The best concentration of these three systems is 0.3%. Then through performance evaluation of resistance to temperature and salinity, adsorptivity, emulsitify and stability, SHPC7 with better emulsification, resistance to temperature and salinity and ultra-low interfacial tension was selected, whose limitation to temperature, salinity, and Ca²⁺&Mg²⁺ is 95℃, 14.71×10⁴mg/L and 5665mg/L respectively.Then the effectiveness for EOR of coreflooding experiments using SHPC7 surfactant flooding system whose concentration is 0.3% was investigated with low permeability heterogeneity artificial cores. Experiments showed that under the same injection time and same concentration, the recovery ratio increment was increased with increasing multiple of injected pore volume. The recovery ratio increment of injecting 0.3PV surfactant slug is the highest, about 5.33% over water flooding, compared with that of injecting 0.1PV and 0.2PV; the increment of recovery efficiency is 1.11%, from injecting 0.1PV to 0.2PV, higher than 0.17%, from injecting 0.2PV to 0.3PV. So, Surfactant Flooding System SHPC7 with 0.2 multiple of injected pore volume should be advised in the field operation proposal for low cost and better effect of EOR.Finally, W92-31 well group was selected and surfactant flooding construction scheme was designed by injecting 0.2PV surfactant, which would reduce the cost and enhance oil recovery.