The Research Of Unsteady Flow Of Viscoelastic Fluid In Eccentric Annulus

Since the industrial application of polymer flooding in the Daqing Oil Field, a preferable driving effect had been achieved .At the same time ,there exist a lot of problem in the rod-pumped wells of polymer flooding compared with water flooding ,such as greater ergogram,lower pumping efficiency ,eccentric way of the sucker rod,shorten period of pumping checking and so on. The flow law in the eccentric annulus with inner cylinder reciprocating of the produced fluid in the polymer flooding wells is studied in this paper. It's obviously that the study has a significant engineering means in the optimizing of the parameters of the pumping unit and in the precaution of the eccentric wear of the socker rod.The movement velocity of sucker rods when fluid of polymer in wellbore changed with time changing during up-down stroke.Then fluid of polymer belonged to unsteady flow of viscoelasticity fluid doing periodical in-and-fro motion in eccentric annulus. In the paper, adopting common conversion Oldroyd-Maxwell constitutive model,the flow equation of the unsteady flow of viscoelastic fluid in the eccentric annulus was established in body-fitted coordinates and the flow equation is discretized by using control volume method;meanwhile calculate velocity profile of flow field ,flow rate by designing programme .Velocity profile of the flow field was obtained by using ADI(Altering Direction Implicit) iterating method. So the numerical solution of the unsteady flow in the eccentric annuli with inner cylinder reciprocating axially is obtained.The numerical solution of the unsteady flow in the eccentric annuli with inner cylinder reciprocating axically is obtained ,and the influences of pressure gradient eccentricity ,stroke and frequency of the inner cylinder on the velocity distribution and instaneous flow rate distribution .The results show that,eccentricity and the pressure gradient have the most important influence on the flow field.Stroke and the frequency of the inner cylinder on the velocity distribution only influence the peak value of instaneous flow rate and velocity distribution .So the existence of radial force is the ultimate cause of eccentric wear of the sucker rods aggravating in the polymer flooding well.Based on the analysis of velocity profile, flow rate and flow regime ,we can calculate the radial force of viscoelastic fluid in eccentric annulus reciprocating flow field , analyse the fluid mobile phenomena, discuss the eccentric wear of sucker rods and tubing using polymer flooding, it can play a key important role in designing job parameter.