Study On Regeneration Rules Of Low Tension Foam System In Porous Medium

The oil fields in China are mostly continental sedimentary reservoirs.In the middle and late stage of oil fields development,the majority of them are in the high containing water and high degree of recovery stage while there have serious formation heterogeneity.What's more,difficulties were met in some oil fields development,such as low permeability oilfield development and heavy oil development,which leading to effect of traditional water injection get even worse.Researchers will pay much more attention on how to improve the recovery of these oil fields.Aiming to solve the problems in severe heterogeneity,permeability,heavy oil and other oil fields exploitation and low tension foam were used,which are effective EOR techniques.Low tension foam has high strength profile control ability as the traditional foam and the oil wash function of the low tension foam,which can greatly improve the swept volume and wash oil field efficiency in order to improve the recovery efficiency at last.The effectiveness of generating stable foam is the key to the success of low-tension foam flooding.It is a dynamic process that the foam in the continuous formation of generation-shattered-and re-generate.The re-generation property of the foam determines dynamic stability of itself.So there has practical significance in the study of low tension foam re-generation law.In the study of the performance,generation,shattered,regeneration mechanism of migration law,as well as blocking properties of the foam,the theoretical analysis,evaluation experiments,core flooding experiments and microscopic visualization experiments were used in this paper.The evaluation of foaming agent has showed that the higher the concentration of foam,the better the performance of them,but after reaching the critical micelle concentration,it's not obvious to increase the concentration of the foam because the adsorption of formation water dilution and formation of the adsorption makes the foam concentration lower.Therefore,crude oil has a negative effect on the generation of the foam.One-dimensional core flooding experiments showed that the injection rate increases,the blocking effect is enhanced.It has disadvantage that too low or too high for foam generation and regeneration of gas-liquid ratio can lead to larger effects on the formation of foam blocking in the medium and high permeability formations.Micro-corrosion model experiments showed that the foam formation is constantly generated-shattered-and re-generate;the flowing process of the foaming agent solution and the gas through the courses of liquid membrane lag,necking separation and film breaking for foam generation,the greater the velocity is,the higher the concentration of the foam can get,the smaller and uniform the foam can generated.The comparison between oil and non-oil foam coalescence experiments showed that the join of the crude oil accelerate the foam burst speed.The burst of the foam were mainly through the drainage effect of the liquid film and the effect of gas diffusion.These two effects make small bubble coalescence into large bubbles and reduce the free energy on the surface of the foam.Long core experiment showed that the propulsion of the foam in layer is in the piston mode.The better ability of the sheared foam across through the layer,the stronger blocking ability can get.At the same time,low tension foam has a strong ability to wash oil,which can greatly enhance the oil recovery.