The Study On Microscopic Porous Flow Mechanism Of Polymer Solutions

Today, the polymer flooding is the enhance recovery technique that is used in the high water oil field, the tertiary recovery researchers have used numerical simulation, physical simulation and nuclear magnetic resonance method validating that the polymer solutions are a kind of viscoelastic fluid. The phenomenon has been observed that the viscoelastic polymer solutions displacing the residual oil are stronger than the purely viscous fluid (glycerin). Studying and describing on the flow characteristics of viscoelastic polymer solution is the basis of studying the displacement mechanism and displacement method. So it is a interesting problem and is paid with particular attention, but the corresponding research are experiment method. The strength and development of the eddy is the main reason which makes the residual oil becoming the flow oil and the sweep efficiency can be enhanced. So the flow characteristic of polymer solution in micro pores can be studied on basis of eddy phenomenon theoretically. This research should be useful in selecting polymer fluids and designing polymer flooding operations. So the following works were done:The constitutive equations describing polymer rheology are analyzed by combing the typical rheology of polymer solutions. Lots of constitutive equations are studied according the rheology of the polymer solutions. Thereafter, the Upper-Convected Maxwell constitutive model and PTT model which can more accurately describe the rheology of polymer is selected.The mathematical model concluding the continuity equation, momentum equation and UCM constitutive equation is established. The governing equations are discretised adopting the non-staggered grid finite volume method numerically and the equations are solved by strong implicit (SIP) method. The stream function contours, velocity contours and stress contours are drawn, the effect of the elasticity on the micro sweep efficiency are analyzed. The results show that We is the key factor that affect the eddy size, sudden contraction velocity distribution and stress distribution. The bigger is the We, the larger is the flow area and the smaller is the residual area. The primary normal stress difference and shear stress increases with the We increase. So the micro sweep efficiency is enhanced.The numerical algorithm is validated by the UCM calculation because of its simple form. The flow characteristic of PTT fluid is studied in a sudden contraction. The governing equation is also discretised by non-staggered grid finite volume method. The effect of elasticity and extensional factor are analyzed.