Cathodic protection of oil tube casing
Oil tube casing is an additional layer of protection to protect the internal main oil pipeline from being squeezed by the stress of the external rock soil layer and strengthen its transport stability. Because the well is thousands of meters underground, the deep casing is under tremendous pressure. With the use of the pipeline for a long time, after the shortest 16 months and the longest 5 years, the oil tube casing will have different degrees of erosion, misfracture, deformation, rupture, serious and even damage. This can result in a significant loss in the efficiency of the well.
The cathodic protection of oil tube casing has several characteristics.
Because of the depth of the oil well and the complex environment, it is necessary to use the impressed current protection method in cathodic protection to effectively ensure the efficiency of the oil casing cathodic protection. Secondly, in order to cope with the pressure of deep soil and the possible corrosive environment, the deep-well anode must be used as the auxiliary anode in the impressed current method. The deep-well anode has the advantages of small weather influence, stable grounding resistance, small stray current interference, small footprint, long service life, convenient installation, etc., which is suitable for dense pipe network and harsh working conditions.
In practical applications, in areas with more Wells or more dense Wells, an anode deep well is needed every two to four Wells to serve as the positive end of the Yin protection system. Anode Wells are usually located near several Wells to ensure that the cathodic protection current can cover all Wells in the area.
Finally, between the above two points, the impressed current cathodic protection of the well must also use a custom potentiostat to provide sufficient, suitable, cathodic protection current. The cathodic protection current will be sent from the potentiostat, flow to the anode deep well as the anode section, and then transported through the soil to several nearby oil tube casing, and make it become the cathode is also protected, and finally return to the potentiostat by the surface wellhead junction, forming a complete closed loop.
