Study On The Physical Properties Of Foam Characterization And The Foam Flooding

Foam flooding, served as a kind of feasible viscoelasticity oil displacementsystem, is used for practical production of oilfield. By means of indoor physical simulation experiments, it can determine the best foaming system and the concentration, the methods for characterizing the bubble size, and the seepage conditions and the sealing ability that bubbles have in the porous media. On this basis, it determines the effect of foam flooding enhancing oil displacement efficiency by extreme recovery experiments of foam flooding, and determines oil displacement effect that foam flooding has on microscopic remaining oil by freezing casting thin sections. Using one-dimensional heterogeneous model, the two-dimensional plane model and three-dimensional model to make physical simulation experiments, it can determine swept volume of the foam flooding and thecontribution ratio of swept volume to the recovery. The results are as follows.Through the establishment of the relationship among the dimensionless concentration of foaming agent, dimensionless foaming volume, and dimensionless foaming half-life period, it determines the best theoretical concentration of foaming agent is 0.8470%-1.2626%, and the best foaming volume and the concentrationwindow of the best foaming half-life period is gradually increasing with the increase of the temperature. Oil resistant sensitive coefficient(SFB) is used to evaluate the stability of foaming agent in the oil, the sensitivity of which is divided into six levels.The smallest representation unit of bubble image demands that the number of bubbles in a single image is higher than 120. The concepts of the disturbance element and the disturbance unit are used to accurately evaluate foaming capacity of foaming porous media from the mechanism, and when the number of the disturbance unit reaches more than 100±20, the homogeneous degree of foam is better. The average particle size of bubbles has a relationship of 1.23-1.51 times with the mainstream throat diameter. Bubble flow-block mode is divided into "big bubbles-small resistance", "small bubbles-without resistance", "matching bubbles-appropriate resistance". When the critical capillary number Nc* is about 10-4, bubbles play the grouping effect, it eliminates macroscopicperformance of the phenomenon of "Thomas hearns step", which presents "grouping" effect. The maximum peak pressure and core permeability in the bubble plugging experiments show the negative correlation relationship.The permeability is higher, and the plugging effect is better, which reflects the principle of "Plugging the big but not blocking the small". The results in shunt volume experiment show that level difference for 6 is served as the turning point of shunt volume ratio which is greater than 1. When the ratio of the mainstream throat diameter and average bubble diameter is greater than 0.911, the ratio of shunt volume rate is 0.98, which implements equal mobility flow. Considering the effect of shunt volume flow and the impact of injection pressure, the reasonable ratio of shunt volume flow is 0.777 and the ratio of bubble particle size and throat radius is 0.826.The experiment results of one-dimensional core foam extreme oil displacement efficiency show that the phase recovery rate during the phase of oil displacement is 17.8%, the contribution rate of the oil displacement efficiency in improving the recovery is 71.62%. Oil displacement effect of natural core is also related to the pore structure at the same time. The separation is better(pore structure is more simple), and oil displacement effect is better. The technologies of freezing production of the casting thin sections and information acquisition of ultraviolet fluorescence inspiring all band quantitatively determine the big five kinds of microscopic remaining oil. The effect of foam flooding shows that the number of the remaining oil in oil membrane reduces from 11.87% to 9.25%; the number of the remaining oil in clusters(small scale) increases from 3.61% to 3.70%. The number of the remaining oil in clusters(large scale) reduces from 28.16% to 17.85%. The number of the remaining oil in oil column reduces from 15.66% to 11.42%. The number of the remaining oil in dead-end reduces from 0.54% to 0.02%.The change in length of residual oil saturation of presents that from the former 3 points to the middle 4 points, then to the latter 3 points in one-dimensional heterogeneous cores, the trend of residual oil saturation increases in turnfrom injection side to production side in the process of foam flooding. Residual oil saturation is higher, and the ratio of heavy component is higher. Along the path, the ratio between light and heavy component on the entrance side is smaller than that on the export side. The results of two-dimensional homogeneous plate model show that swept volume of foam flooding is more increased by 30.54% than that of water flooding stage, and oil-washing efficiency is moreincreased by 4.55%. The main contribution of improving the recovery comes from the effect of expanding the sweep volume(89.33%). The results of two-dimensional three layers’ inhomogeneous plate model show that the ascensions of swept volume and oil displacement efficiency are both the highest in the foam flooding for low permeability layer, reaching 12.56% and 12.56% respectively,which shows the major contribution of improving recovery on the whole comesfrom the effect of expanding the sweep volume(93.27%). Three dimensional three layers’ inhomogeneous plate core adopts the electrode method to measure oil saturation, and gray image processing method can accurately calculate the result of recovery(error up to 2.29%) that ascensions of swept volume and oil displacement efficiency are both the highest in the foam flooding for low permeability layer.Through the foam physical properties and oil displacement effect of foam flooding in this paper that provides a theoretical basis for production in oil field and indoor experiment.