Study On Waxing Characteristics And Paraffin Removal Technology Of Oil Well

As China's crude oil is rich in wax,the process of oil production is bound to be accompanied by waxing problem.Waxing in the wellbore has a deep influence on the production of oil wells and its solution has a direct impact on the oil production and economic benefits.In general,the wellbore waxing will reduce the oil cross-sectional area,decrease the utilization of the tubing,heighten oil flowing resistance,increase the sucker rod resistance and burden.When the wax is serious,it will make the sucker rod stuck in the tubing,and even cause the sucker rod breakage.In order to avoid or reduce the adverse effects and hazards greatly caused by waxing in the wellbore,it is necessary to research the theory of wellbore waxing,mechanism of wax deposition,wellbore temperature,waxing rate and so on,so as to better predict the production dynamics in the wellbore.Through the establishment of dynamic prediction model of paraffin precipitation in the process of oil production,it provides deep understanding of the waxing dynamics and theoretical guidance for the implementation of clearance and anti-wax technology in the well.This paper mainly carrys out the following work:Firstly,on the basis of a large number of domestic and foreign research,the paper summarizes the related theories of waxy crude and the status of wellbore temperature field.At the same time,the dynamic models of wax deposition are summarized and the evaluation of models are carried out.Secondly,for the problem of wax formation in the wellbore,based on the theory of heat transfer and the principle of energy conservation and momentum conservation,the prediction model of temperature in the wellbore is established.The fourth-order Runge-Kutta method is used to solve the problem,and the prediction result is highly accurate.Comparing and analyzing the methods of determination the crude oil initial crystallization temperature point,the differential scanning calorimetry is used to determine the crude oil initial crystallization temperature point of well A in Block X.According to the temperature of the wellbore and the temperature of initial crystallization temperature point,then the depth of the wax is determined,which provides the theoretical basis for the anti-wax operation.Thirdly,research on dynamic prediction model of waxing in the wellbore.Considering the influence of molecular diffusion and shear dispersion on wax deposition,the dynamic prediction model of wax thickness in the wellbore is established,and the Newton iterative method is used to solve the problem.Based on the gray theory of sliding average,the prediction model of waxing speed in the wellbore is established.On the basis of reasonable assumptions,the prediction model of the wax removal cycle in the wellbore is established.The research on the dynamic prediction model of waxing in the wellbore is to lay the foundation for ensuring the safe production of the oil well,saving the cost and making reasonable measures to prevent waxing.Fourthly,according to the compiled program of the prediction model of temperature and waxing in the wellbore,the influence of yield,water content and production time on well temperature profile and wax profile are analyzed respectively.Fifthly,through the established model and the compiled software,it is applied to the block X and takes Well A as an example to carry out the relevant calculation.Above all,according to the prediction model of wellbore temperature,the wellbore temperature profile of well A is determined,and by combining the measured wax precipitation temperature,the wax precipitation depth of well A is determined.Then,according to the prediction model of wellbore temperature and wax profile,the wax profile of well A is determined.What's more,based on the actual statistical data of well A,the wax velocity model is established by sliding average gray theory,and the waxing velocity of well A is fitted and predicted.Finally,the wax removal cycle of well A is determined by the prediction model of wax removal cycle.The results of the models are consistent with the actual situation.Finally,based on the existing problems of the Block X,comparing the current clearance and anti-wax technology,washing technology of vacuum hollow sucker and microbial wax protection technology suitable for the block are selected.In the application of washing technology of vacuum hollow sucker,the depth of the hollow rod is determined,the strength of the column is checked,the hot wash parameters are determined and the effect is evaluated by field application.