| The air-foam flooding technology is considered to be a very promising method to enhance oil recovery, because of its great development potential to decline air/oil ratio, increase oil production and improve displacement efficiency. The main mechanism is that the foam could be injected and penetrated in the low permeability layer as the injection pressure increasing, due to the Jamin action, the flow resistance will be increased when the foam into the formation, so as to improve the sweep efficiency and achieve the purpose of enhanced oil recovery.Based on theory and laboratory experiment, the numerical simulation technology is used to research the influence of the reservoir characteristics impact on the air-foam flooding technology and the application scope of the air-foam flooding technology.The main facror of the air-foam flooding technology are the variation coefficient of permeability Vk, different oil viscosity, well pattern and well spacing, formation rhythm, vertical permeability and so on. The research is to provide the theoretical basis for air-foam flooding on different oil field.With the geologic condition of Wen 120 reservoir in Huabei Oilfield, the main research is the selection, evaluation and the sealing characteristics of foam system to get the foam system X-1 of with good foamability and stability, the effective concentration is 0.1%. When the gas fluid ratio is arouse from 1:1 to 1:2, the resistance factor can reach the maximum value and at the same time the sealing characteristics of air-foam is the strongest. With the core permeability increased, the sealing characteristics of foam system increased,but when the permeability increased to a certain extent, the foam sealing characteristics began to decline slowly, the break point is 1000×10-3μm2. When the foam could be injected in porous medium, the resistance factor RF is arouse from 30 to 90, the residual resistance factor RRF is 2.3, the foam systerm could plug high permeability zone and high capacity channel effectively.Through the laboratory experiment study to get the foam system parameters, the numerical simulation technology is used to research the influence of the reservoir characteristics and well pattern impact on the air-foam flooding technology, the results show that for the weak, medium and high heterogeneity reservoir, when the injection slug is 0.4PV, the enhanced oil recovery can reach the maximum value is 13%, 23%, 25%. So foam flooding is suitable for medium and high heterogeneity reservoir. For the high viscosity of the crude oil, the air-foam flooding effect is most obvious.When air-foam injection slug is 0.6PV and oil viscosity is 25mPa·s, the enhanced oil recovery can reach 24.11%, when the oil viscosity is 46mPa·s, the enhanced oil recovery is 24.77%, when the oil viscosity is 60mPa·s, the enhanced oil recovery is 24.54%. When air-foam injection slug is 0.6PV and the oil viscosity is 100mPa·s, the enhanced recovery is 22.63%. About well pattern impact on air-foam flooding to enhance oil recovery, nine-spot well pattern is suit for low permeability layer, five-spot well pattern is suit for low-medium permeability layer, straight line method is suit for medium-high permeability layer, seven-spot well pattern is suit for high permeability zone. Under the condition of the most serious aeolotropism Vk=0.77, the smaller well spacing, the better water flooding. About the rhythm of reservoir impact on air-foam flooding to enhance oil recovery, air-foam flooding for EOR in positive rhythm reservoir is the highest, the cumulative injection water is the most, development effect is the best; the reverse rhythm reservoir recovery rate is the lowest, cumulative injection water is the least, development effect is the worst. |
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