Study On Wellbore Electromagnetic Coupling Heating Mechanism Of Heavy Oil Thermal Recovery

Petroleum resources will be one of the most important energy sources in the world for a long time to come.Heavy oil is an important component of petroleum hydrocarbon energy and has many times the reservoir potential than conventional crude oil resources.Thermal recovery of heavy oil is a common method for heavy oil production in oilfields.The current heavy oil electric heating method not only has disadvantages such as low heating efficiency,large power consumption,low safety and poor reliability,but also increases the production and maintenance costs.Therefore,in order to solve the above problems,this paper proposes a new electromagnetic coupling heating method for heavy oil wellbore.In this paper,by analyzing the oil production process and wellbore structure characteristics of the pumping unit,the heating windings are wound on the outside of the sucker rod and fed into the alternating current,the excited magnetic field generates eddy currents in the wellbore,and then the heavy oil is heated by Joule heat.Based on the given basic assumption,a three-dimensional eddy current finite element simulation model for wellbore electromagnetic coupling heating is established.The simulation model is applied with frequency current excitation to improve the eddy current loss distribution,the magnetic induction intensity,eddy current density and eddy current loss distribution in the simulation results are analyzed,and the distribution rules are summarized.In order to further improve and discuss the influence of higher frequency on the wellbore eddy current loss distribution,the distributions of magnetic induction intensity,eddy current density and eddy current loss under the same current excitation at different frequencies and the same heating power at different frequencies are studied respectively.The simulation results show that the variation of magnetic induction intensity,eddy current density and eddy current loss becomes smaller with the increase of frequency,and the variation trend tends to be stable with the increase of frequency.When the heating power is the same,the eddy current loss in wellbore is mainly distributed in sucker rod and tubing,and the distribution of eddy current loss in sucker rod,tubing and casing basically does not change with frequency.Then,the effects of alternating current frequency and heating power on wellbore temperature and heavy oil temperature are studied by simulating wellbore temperature field.When the power supply frequency is low,increasing the frequency can significantly increase the heating temperature.When frequency is high,temperature rise does not change significantly with frequency,and there is a linear correspondence between heating power and outlet temperature of heavy oil,which is of reference significance for setting target temperature regulation power.At last,the heating parameters required by different frequencies when the same temperature rise is reached in the process of heavy oil lifting are obtained through simulation.The electromagnetic coupling heating method of heavy oil thermal recovery wellbore proposed in this paper has the advantages of simple structure,uniform heating,high heating efficiency,electric isolation and improved safety performance,etc.It provides a new design idea and optimization scheme for electric heating equipment used in heavy oil thermal recovery.