Application Of Viscoelastic Fluid Dynamics To Prevent Partial Wear Of Pumping Well

A series of problem has been found after polymer flooding putting into effect in DaQing oilfield, which condition of sucker rods under force action becomes worse, serious partial wear of sucker rod has made the rod break and drop, the cycle of pump inspection has been shorten. This is briefly because viscoelasticity of produced fluid. This paper will focus on the flow of polymer solution in pumping well bore.In this study, we developed first theoretic study of viscoelastic fluid dynamics and found Oldroyd-Maxwell constitutive equation which fits for describing viscoelastic flow characteristic law of produced fluid from polymer flooding well. Flow equation of viscoelastic fluid in well bore has been built. We analyze velocity distribution of flow field and found that normal stress acting on sucker rods is caused by unsymmetry of flow field and elasticity of fluid. The way to calculate normal stress has also been found. Normal stress exists in well bore after polymer flooding, which has been explained theoretically. The main reason that leads to partial wear is elasticity of produced fluid and eccentricity of rod string.We develop next polymer solution dynamics experimental research. The value of normal stress acts on sucker rod string due to polymer solution and eccentricity of sucker rod string have been measured quantitatively by experiment. The relation among normal stress value> flow velocity and eccentricity of sucker rod under different density of polymer solution condition has been decided. Variable law of resistance is discussed when polymer solution flow through sucker rod, coupling, centralizer, pump valve and pump barrel. Basic reason that causes partial wear seriously between sucker rod and tube and the cycle of pump inspection shorten has been gained, which is not totally caused by up force after polymer flooding.It shows that basic reason that cause partial wear is because of normal stress existing when sucker rod move in polymer solution of polymer flooding well bore, which is gained by combining theory with experimental research. This conclusion provides theoretic guide for formulating measure that slow down and prevent partial wear between sucker rod and tube.