Mechanism And Promotion Method Of Phase Transition/Removal Of Wax Layer

The crude oil produced in most oil fields in China is high waxy crude oil,which makes it have three high characteristics,namely high waxiness,high freezing point and high viscosity.When the temperature is high,the wax is in a dissolved state,and the crude oil exhibits the rheological properties of Newtonian fluid;as the temperature decreases,the wax gradually crystallizes out,and the viscosity rheology of the crude oil increases,which turns into a Newtonian fluid.When the wax crystals reach 2%-3%,a three-dimensional network structure can be formed,resulting in loss of fluidity of the whole crude oil,and wax deposition problems: reducing the effective inner diameter of the pipeline,increasing the conveying pressure,reducing the conveying capacity of the pipeline,and increasing The frequency of pigging is even causing a wax blockage accident.In the Lasmo field,there have been very serious wax deposition problems,and the cost of wax deposition problems has exceeded $100million.Therefore,on the basis of mastering the characteristics of wax deposition,the development of high-efficiency low-energy wax cleaning technology is of great significance for ensuring safe production of crude oil and reducing energy consumption.The wax cleaning technology currently used has limitations.The thermal wax cleaning technology is economical but takes a long time.The chemical wax cleaning technology is efficient but costly.Therefore,the development of the thermal-chemical coupling wax cleaning technology not only meets economical cost and high efficiency,but also meets high efficiency.Achieve the effect of energy saving and emission reduction.In this paper,the laws of hot wash and wax removal were studied by simulation and experimental methods,and the weak link of hot wash wax was clarified.The chemical wax removal characteristics of different surfactants were investigated.On this basis,the mechanism of thermal-chemical coupling wax removal and its promotion were analyzed.The main contents are as follows:(1)The VOF method was used to track the interfacial changes of the two-phase flow during the wax removal process.The numerical simulation method was used to study the multiphase flow and the wax removal rate under different heat wash medium temperatures and flow rates.Eight feature points were selected as the basis of quantitative research to quantitatively analyze the influence of water temperature or water flow velocity on flow pattern and wax removal rate.It is concluded that the flow velocity has a greater influence on the flow pattern than the water temperature.When the flow rate is 0.5 m/s,the flow pattern of the liquid wax is mainly a suspended flow.At this time,it is advantageous to combine with a chemical agent.(2)The waxing tube of the same amount of wax was subjected to a hot wash and wax removal experiment using a self-made rotary clearing(knot)wax system,and thecomponents of the wax were dissolved at different times by gas chromatography.The effects of different thermal parameters(including water temperature,wall temperature,wax layer thickness,rotation speed and temperature difference)on the wax removal effect were investigated.The results show that the wax removal effects of different water temperatures are inconsistent.The higher the wall temperature,the faster the average wax removal rate.When the temperature difference between the water temperature and the wall temperature is kept constant at 60 ?,the wax removal rate decreases first and then increases with the increase of the wall surface temperature.The flow rate increases and the water flow rate increases.The most unfavorable wax thickness is present during the wax removal process.(3)The self-made rotating clear(knot)wax system was used to study the wax removal effect of different surfactants,and the surfactant suitable for Daqing crude paraffin was selected.The surfactant is subjected to a compounding experiment to analyze the waxing effect of different ratios,and a suitable compounding ratio is preferred.The results show that the anionic surfactant AES and the emulsifier OP-10 have a good effect on Daqing crude oil paraffin.After comparison,the effect of clearing wax is most obvious when the ratio of AES and OP-10 surfactants is 1:2without considering the heating.(4)The self-made rotary wax removal device was used to analyze the wax removal effect of the preferred single surfactant under the synergy of heat and chemical,and the influence of temperature field(including water temperature,wall temperature and constant temperature difference)on the wax removal effect was analyzed.The effect of clearing the surfactant on the wax removal under the influence of the temperature field was analyzed,and the best conditions in each case were obtained.Compared with the single chemical wax removal technology,the compounding ratio is 2:1,the water temperature is 50 ?,and the wax removal efficiency is increased by 1.7 times.Compared with the single hot wash wax removal technology,the compounding ratio is 2:1,and the waxing effect with a water temperature of 50 ? is better than the water temperature of 60 ?.It can be seen that the thermo-chemical synergy has a significant effect on the wax removal,which can significantly improve the wax-cleaning ability of warm water.