Experimental Research On The Impact Of Vibration On Foam Flooding

Due to the high residual oil saturation in the reservoirs after water flooding recovery,several oil production technologies are solicited to improve the oil recovery rate.Among these technologies,foam flooding is largely used in the world in order to enhance the oil recovery efficiency;because of its low cost and it has good environmental effects.The performance and stability of foam are the main factors which should be controlled in the foam flooding process.In order to improve the foam properties,the low-frequency resonance wave is associated to contribute on the performance and stability of foam system;and improve the sweep efficiency by subsequent water flooding and further improve the oil displacement capacity.To reach the above objectives,the cores flooding experiments were carried firstly to analyze the influence of low-frequency resonance wave on the formation including the seepage law of water flooding,reservoir rock properties and the crude oil viscosity.The foam system was composed of hydrolyzed polyacrylamide(HPAM)with the molecular weight of 5 million and 10 million,and the surfactant named BK-6.In the foam solution sample preparation,a concentration of 0.5%of surfactant and 0.15%of polymer(HPAM)were used,a simulated formation water(containing Na Cl:70%,Ca Cl₂:12%,Mg Cl₂?6H₂O:18%)was prepared.Based on the foam system,we have investigated the impact of vibration on the foam characteristics,including the foaming performance of static foam system and its stability,the plugging performance and stability of dynamic foam system.The foam synthetic value and the half-life were measured to evaluate the foaming performance and stability of the static foam system respectively.While the maximum resistance factor and the period of the maximum resistance factor were intended to analyze the performance of the dynamic foam system.After the investigation of the static and dynamic performance of foam system,the EOR efficiency by foam flooding was evaluated.In order to analyze the oil recovery increase by applying vibration,0.15 PV of foam liquid and 0.45 PV of nitrogen gas were injected into the sand-filling tube model.In the way of three alternates injection by 0.05 PV of foam liquid and 0.15 PV of nitrogen gas.The foam flooding process should give place to the surfactant flooding process when the foam is destroyed in the porous media.Therefore,the low-frequency vibration was coupled to the surfactant flooding to evaluate its influence on the mechanisms including the oil washing efficiency,emulsifying properties,dynamic adsorption and the diffusion performance of surfactant.Lastly,the EOR efficiency analysis by surfactant flooding under and without vibration conditions was carried out.The experiment results showed that the low-frequency resonance wave has a potentiality to improve the oil recovery efficiency by water flooding,while the permeability and wettability of the reservoir rock,and the oil and water relative permeability were improved,meanwhile the capillary pressure and the oil viscosity were reduced.It was found that the foaming performance and the stability of the static foam system were optimized at the optimum vibration frequency and acceleration.In the case of the dynamic foam system,the vibration time has no effect on the maximum resistance factor,but a longer vibration time can enforce the stability of foam.The frequency and acceleration of vibration have effect on the maximum resistance factor and the period of maximum resistance factor,but the best value of these vibration parameters should be selected in oilfield test.Under the condition of low-frequency wave,the oil recovery efficiency could be improved through both the measurements of profile control with foam and surfactant flooding.