Research On The Special Power Supply Control System For The Pulse Current Protection Of Oil Well Casing

With the proceeding of oil production,the corrosion of oil well casing is becoming more and more serious,which directly affects the further exploitation of oil field.It is indicated that the external corrosion of oil well casing is the main one,and the cathodic protection is an effective technique to control the external corrosion.At present,in out country,DC-type potentiostat implement is widely used in impressed current cathodic protection of well casing.Years of practice shows that this technology is a very economical and effective method to prevent the corrosion of oil well casing.But at the same time,the technology has some defects,which is the deep well casing can not reach the actual needs of the protection depth with the DC cathodic protection.The related research shows that the protection depth of the DC current cathodic protection can only reach about 1500 meters in the oil well casing cathodic protection,using the pulsed current cathodic protection technology can extend the protection depth over3000 meters.At present,this technology is still in the initial stage in China,and has not been applied in large scale.This paper is based on the requirements of pulse current cathodic protection technology in oil well casing,and research on the special power supply control system for the electric current cathodic protection of oil well casing.Firstly,the overall design scheme of the pulse power supply is determined;Secondly,a special power supply main circuit is designed,and introduced its working principle.Finally,according to the main circuit,we construct the control circuit to realize the real time control.Three-level closed-loop control strategy was adopted to realize the adaptive regulation of power supply.The control system is designed with SH99F100 as the core control chip.and adopt high frequency switching technology,digital technology and soft switching technology to control the cathodic protection power supply for oil well casing pulse current.At the same time,we designed the remote monitoring system which is based on GPRS wireless communication technology,realize the digital and centralized management of the oil well casing pulse current cathodic protection.Based on the above analysis and design,we have developed the control system of the pulse current cathodic protection of oil well casing,and make a prototype.The simulation experiment of pulse current cathodic protection of oil well casing is carried out by using theprototype,and tested the power control system.The results show that this control system can make the power supply generate pulse current which frequency,amplitude and duty cycle can be adjusted independently.It can make the protection potential in the best protection range.It also can realize the automation,intelligent operation of power supply,and achieve the expected targets.