Mechanism Study Of Foam Transport And Its Flow Behavior In Porous Media

Study of foam fluid is of great significance for the efficient development of oil fields,there are a lot of problems of foam application duo to its complex properties,such as the effective existence of foam fluid in the formation,range of foam working and the applicable conditions of foam fluid.We usually adjust the parameters according to the experience in field application,which can't provide the proper interpretation and solutions,and the mechanism of foam transport in porous media and its flow behaviors had not be studied intensively.Accordingly,the fractal theory and the level set method are introduced to quantitatively describe the foam structure and trace the change of foam interface.On the basis of these,two aspects related to foam migration are studied.The first one is macro dynamic migration characteristics research based on plenty of foam structure.Firstly,the foam images are collected by Foamscan or micro visualization device.Secondly,a large number of images are processed.Finally,the processed images are calculated by programming,and the fractal dimensions are obtained.In this work,the structural evolution and the fractal characteristics of foam in porous media are studied.The second one is the study of micro dynamic migration mechanism based on level set method by analyzing a small amount of foam.Firstly,foam migration process in simple pore throat is simulated and analyzed,including Jiamin effect,snap-off mechanism,coalescence mechanism and selective migration mechanism;Secondly,foam migration characteristics in variable diameter pore,double cone,complex pore throat are simulated,and the effectiveness of simulation is verified by results based on visualization experiments,then this method is extended to the complex porous media.At the same time,the research of foam fluid behavior in porous media is carried out based on in situ heated foam system,mainly focusing on the analysis of the temperature distribution.Besides,the foam seepage mathematical model is proposed by coupling wellbore and formation.The results show that a large number of foam has fractal characteristics and the foam fractal dimension ranges from 1 to 2,the greater the fractal dimension is,the more serious bubble coalescence will be.A structure evolution model based on fractal theory is established for the evolution of foam structure.The model shows that the fractal dimension of aqueous foam correlates non-linearly with the changing of time,meanwhile,this relationship can be well captured by an exponential equation.The temperature and concentration changing lead to the changes of the trend,but does not affect the applicability of the model.Foam in the dynamic migration in porous media has fractal characteristics as a whole,however,fractal dimension is independent of the time change,and related to their own properties and environmental conditions.Temperature,concentration of foaming agent,pore structure and other influence parameters on foam migration characteristics shall not change the constant changing trend of foam fractal dimension over time,but affect the foam fractal dimension values.Migration law of a small amount of foam is mainly affected by bubble deformation mechanism,namely,the pressure that the bubble suffers when it get through pore and throat associates with bubble deformation degree.At the same time,the surface tension is proportional to pressure,and the inverse of pore throat radius is linear correlation with the pressure;Snap-off is divided into two stages,one is the burst of big bubble,the other is the coalescence of small bubble;The bubbles volume reduces under the process of coalescence with vibration;Foam has priority in large pore at a micro level.Foam seepage law is mainly manifested in terms of plugging and profile control,meanwhile,foam also has the characteristics of adjusting the temperature distribution.