Study On Well String Mechanics Of Polymer Flooding In Oilfield

With the maintenance consumption of oil fields,most oil fields are at the end stage of development,which results in the augment of moisture content and the production decrease in crude oil Polymer flooding technology can greatly improve the mobility ratio of displacement solution to crude oil,expand the swept volume of displacement solution,and thus slow down the rise of the water content of the produced fluid.As the most mature and effective chemical flooding method,polymer flooding techniques has been extensively used a majority of oil fields in China.In order to achieve polymer solution injection into the reservoir of the target oil well,construction is generally divided into three different working conditions,namely,the running process of the polymer injection string,the setting process of the packer at the lower end of the string and the injection process of polymer solution.In order to achieve accurate injection of the target reservoir and safe and effective construction in each working condition,Therefore,it is necessary to conduct dynamic research on the tubular column of each operating mode.This paper studies the tubular column of different working conditions in the following aspects:The fluid in polymer flooding injection well is simplified into a power law fluid,and the calculation model of pipe body and collar fluid resistance during the running process is established.On this basis,the simulation model of longitudinal vibration during the running of the pipe string is established,and the influencing factors of the axial load of the pipe string and the hook load are analyzed,which has practical guiding significance for the operation of the workover rig in the running of the pipe string.The transient fluid pressure simulation model in the packer setting process was established,and the axial vibration simulation model with the fluid pressure as the excitation was established on this basis.The change rule and influencing factors of axial displacement in the packer setting process were analyzed.The fluid density and index were positively correlated with displacement,and the consistency coefficient and flow velocity difference were negatively correlated with displacement.It has guiding significance for the installation and positioning of packer.Considering the radial strain,circumferential strain and axial strain produced by Poisson effect under internal pressure,as well as the seepage boundary required by daily injection and the transient flow boundary of surface plunger pump,a simulation model of axial fluid-structure coupling vibration of pipe string during injection in polymer flooding Wells was established,and the variation law and influencing factors of axial load of pipe string were analyzed.The fluid density,consistency coefficient,power law index,permeability,and rotational speed are negatively correlated with the maximum load,enabling the prediction of axial creep.