Investigation Of The Movement And Coalescence Characteristics Of Oil Droplets In Produced Liquid By Alkali-surfactantpolymer Flooding

Alkali-surfactant-polymer flooding can improve the oil-water current ratio and the swept volume of oil layer, so it is able to increase the oil recovery remarkably. However, there exists a great deal of residual alkali, surfactant and polymer in the produced liquid by A-S-P flooding and make the produced liquid own high viscosity and density and some suspended solids. The produced liquid is emulsified so seriously that it is difficult to separate the oil and water. The traditional processing technologies and separation equipment do not meet the requirement. Based on the high speed photography and image processing technologies, the movement and coalescence characteristics of oil droplets in the produced liquid and the stability of the produced liquid were studied. Then the acting mechanisms of the influencing factors were all summarized. The main conclusions are as follows:(1) As pH value(8.5~11.0) of the produced water rises, the velocity of an oil droplet firstly decreases and then increases. When the pH value equals 9.7, the minimum velocity exists. When all the other factors are certain, the velocity of an oil droplet in the liquid which contains the alkali, surfactant and polymer is less than what in the liquid only containing the alkali and polymer. The reason is that surfactant can improve the resistance ability to the electrostatic shielding.(2) Polymer can help to increase the viscosity of the produced liquid. The velocity of an oil droplet is proportional to the reciprocal of the polymer concentration. When the produced liquid only contains the polymer, the velocity of an oil droplet is one point five or three times as faster as what in the liquid which contains the alkali, surfactant and polymer. The reason is that alkali can help to the stretch content of polymer molecular chain.(3) There exists the quadratic function between velocity of an oil droplet and surfactant concentration when the produced liquid just contains the surfactant and polymer. However, surfactant has little effect on the velocity when the water is strongly alkaline. When the pharmacy concentration and temperature are constant, there exists the quadratic function between velocity of an oil droplet and its diameter. When all the other experimental conditions are constant, high temperature helps to the oil-water separation. The velocity is proportional to the reciprocal of temperature.(4) Two hundred experimental data were used to get the relationship between the drag coefficient and the Reynolds number. The Reynolds number is between 10-5 and 10-2. The calculated drag coefficient is larger than 24/Re and this has something to do with the shear force of the continue phase, the internal eddy and the carrying effect of polymer net. With all the correction factors, CFD software was used to simulate the realationship between the lifting movement of oil droplet and the viscosity of the continue phase and what between the lifting movement of oil droplet and its diameter. Under the same condition, the simulation value coincides with the experimental value. This conclusion indicates that all the modifications about the sedimentation formula of Stokes are reliable.(5) As the polymer concentration rises, the film drainage and oil droplet coalescence become more difficult. When the liquid contains the alkali, surfactant and polymer, the bigger pH value makes the coalescence time firstly increase and then decrease and the higher viscosity makes the film drainage more difficult and costs more time than the oil droplet in the liquid containing the alkali and polymer. When the other experimental conditions are constant, there exists the Gaussian function between the coalescence time and surfactant concentration. Because of the alkali, it will cost more time when the liquid contains the surfactant and polymer.