Study On The Rule Of Wax Deposition And Paraffin Remover And Inhibitor Of Crude Oil On Oil Pipeline

In recent years,more and more attention has been paid to the flow barrier caused by the wax deposition of crude oil in the oil pipelines.With the focus of domestic oil and gas fields shifting to northwest China,the extreme low temperature in winter in northwest China has made wax deposition more prominent.Back pressure,high pigging frequency and even pipeline burst caused by wax deposition appeared in oil pipelines of many oilfields,bringing great challenges to stable and increasing production.Therefore,the research of an efficient way for the wax removal and prevention system as well as the wax deposition rule are of great significance to the flow guarantee of oil pipeline.Based on the SHB pipeline crude oil in an oilfield of the northwest China comprehensively analyzes the physical properties of crude oil and waxes,and specifically develops the high-efficiency paraffin removers QSH-45 and QSH-80 and the paraffin inhibitor FSH-1,which are evaluated in accordance with the standards of oilfield chemicals,optimizing the best working conditions of the wax removal and control system.In addition,the effects of additives on the properties of crude oil and wax as well as the effects of temperature and other factors on wax deposition in the surface pipelines are also investigated by the author.To solve the problem of low efficiency of commercial paraffin remover to crude oil in target block,and after determining the physicochemical properties of crude oil and wax,the author developed the paraffin remover QSH-45 with the best wax solubility at 45℃,the formulation of which is 31.32%cyclohexane+20.88%QL-2+10.44%AH-1+31.32%AH-2+1.75%butyl stearate+1.75%stearic acid+1%AES+1.5%S-80.And the wax removal efficiency can reach 21.1 mg·min^-1.Besides,the author developed the paraffin remover QSH-80 with the best wax solubility at 45℃,the formulation of which is:28.8%cyclohexane+28.8%QL-2+28.8%AH-1+9.6%aviation kerosene+0.25%butyl stearate+1.75%stearic acid+0.25%AES+1.75%S-80.And the wax removal efficiency can reach673.6 mg·min^-1.In view of the fact that paraffin wax and microcrystalline wax account for50.7%and 15.9%respectively in SHB crude oil wax,and by screening the effect of monomer ratio on control rate,the ternary polymer was synthesized by tetradecyl methacrylate(C₁₄MC)-benzyl methacrylate（MB）-n-vinyl pyrrolidone（NVP）with the ratio of 10:1:1 and the wax-proof rate was 70.4%at the dosage of 0.2%.The best working conditions of the wax remover were optimized through the dynamic evaluation experiment with the results that the best working conditions for paraffin remover should be:oil temperature 70-80°C,temperature of pipeline wall above 20°C,shear rate at 2500 r·min^-1,and the best working conditions of FSH-1 should be:oil temperature and temperature of pipeline wall 20°C,shear rate at 3000 r·min^-1and action time 3 h.In addition,this study also finds that the wax precipitation point and wax precipitation peak temperature slightly decreased with the addition of wax inhibitor,and though the crystal form of wax remained unchanged,the solubility enthalpy decreased,besides,the degree of aggregation increased and the carbon number increased.The results of cold-finger test show that the large temperature difference of oil wall will increase the wax content of the wax deposition,which will make it more difficult to remove and prolonged wax deposition will slow down the aging rate of wax deposition and increase the average carbon number.And two explanations for the differences between the molecular diffusion wax deposition model and the experimental results are proposed in this study.