Microscopic Mechanism Of The Residual Oil Displaced By Viscoelastic Fluid

To further explore the displacement mechanism of the viscoelastic properties of polymers to the residual oil, upper-convected Maxwell constitutive equation was selected by this paper, flow equations and boundary conditions of the viscoelastic fluid flow in porous road were established by using the theory and method of rheology and computational fluid dynamics, flow field and stress field is solved by using numerical method, but also the stress distribution and force on the residual oil of displacement fluid are studied by using of tensor analysis. Membrane and cluster residual oil deformation are calculated by using of the interface in physical chemistry theory under different displacement fluid. The results showed that:normal deviatoric stress is very small and it is antisymmetric when the displacement liquid is water, that is, the first part of droplets are under pressure, the latter are subject to pull; the power law fluid has the similar characteristics of the normal deviatoric stress, the values of the normal deviatoric stress are not only larger but also the distribution has a mutation compared with inelastic when the displacement liquid is polymer solution, the normal deviatoric stress in the first part of the surface of the droplets are greater than in the second half. Therefore, the viscoelastic of the polymer solution will force the partial stress of the residual oil film in particular to increase significantly. Viscoelastic polymer solution will have a greater level of thrust to the residual oil film, stress difference generated by the asymmetric of normal deviatoric stress on the film surface is mainly due to oil film deformation. Therefore, it is necessary to further analysis the horizontal thrust- the size of horizontal direction partial stress difference of different displacement fluid when flooding, pressure gradient is 0.02MPa/m, the results of the difference of the horizontal direction deviatoric stress pnh show that:The ratio of horizontal stress difference is about 1:10:25 between water, power law fluids and viscoelastic fluids (Borg Wesson number We=0.3), which means that the driving force on the film when the polymer flooding is about 25 times when the water flooding when the pressure gradient is in the same circumstances. The change of pressure gradient does not affect the ratio of horizontal displacement force in the main flow channel and non-main flow channel between the injection wells and recovery wells. For example, horizontal deviatoric stress difference is increased by 10 times which acts on the film when pressure gradient increases by 10 times. The residual liquid film can produce a more pronounced deformation in the drive of elastic displacement solution,leading to a higher microscopic displacement efficiency. This result will help us to understand the mechanism how viscoelastic fluid displaces irreducible oil, so it not only provide a theoretical support for the view that viscoelastic fluid can increase the efficiency of micro-displacement but also has a great theoretical significance and practical value to make further research on developing new displacing agent and oil displacement agent system.