Study On Construction And Adaptability Of Heterogeneous Combination Flooding System For High Temperature And High Salinity Reservoir

The clastic rock reservoir of tarim oilfield are characterized by high temperature,high salinity,strong heterogeneity and low oil displacement efficiency.The existing systems have weak temperature and salinity resistance and poor formation adaptability,so it is difficult to enhance oil recovery by achieving in-depth profile control and oil displacement.In order to solve this problem,this paper has studied a heterogeneous combination flooding system with both dispersed particle gel and efficient surfactant.We have obtained the matching law between the heterogeneous combination flooding system and formation pore-throat,revealed the formation adaptability mechanism of system,which can provide technical support for further enhancing oil recovery of tarim oilfield.The bulk gel with high temperature and salinity resistance was optimized by the ampoule tests,and dispersed particle gel with different particle size was prepared by colloid mill.Then,highly effective surfactants were optimized by reducing interfacial tension experiment.The heterogeneous combination flooding system was composed of dispersed particle gel and surfactant.By means of core physical simulation experiment,the matching law,in-depth migration ability and macro effect of enhanced oil recovery have been studied.The microcosmic matching law have been studied by means of continuous pore-throat model.Then nuclear magnetic resonance imaging,T₂ spectrums analysis and microscopic oil displacement experiment were conducted to study the characteristics of oil-water distribution and the microscopic effect of enhanced oil recovery.The heterogeneous combination flooding system was composed of 0.1-0.2 wt%dispersed particle gel,0.35-0.5 wt%BSSB and 0.4-0.5 wt%APEC-9.Under the condition of high temperature(120°C)and high salinity(20.93×10⁴ mg/L),the oil-water interfacial tension can be reduced to 10^-1 m N/m by heterogeneous combination flooding system.What's more,oil-wet(contact angle is 28.9°)surface can be altered to water-wet(contact angle is 131.6°).The emulsifying effect of system is good,and the viscosity recovery rate of system is up to 90%after sheering.Formation matching coefficient was introduced,and a mathematical model of matching law was established.The optimal formation matching coefficient is 0.20-0.30.In the optimal matching coefficient range,the heterogeneous combination flooding system has good injectivity,excellent in-depth migration and profile control ability.At the same time,the surfactant can significantly improve oil displacement effect,and the increment of oil recovery is 24.31%.Through macroscopic and microscopic formation adaptability experiments,the formation adaptability mechanism of heterogeneous combination flooding system is that it greatly enhanced oil recovery through the synergy of equilibrium oil displacement,which achieved by dynamic in-depth migration and micro-plugging along the process,and efficient oil displacement.