Abstract

This paper describes Mobil Oil Indonesia's (MOI's) experience with their Arun Field Cathodic Protection (CP) groundbeds. With Impressed Current CP, a CP current is impressed onto steel structures to eliminate corrosion cells and to transfer metal loss to the anode. Arun Field CP systems have satisfactorily mitigated external corrosion of steel structures in contact with soil.

In Arun, two types of anode groundbeds have been used; horizontal and deepwell. Initially, horizontal groundbeds were used in Arun. These groundbeds used graphite anodes, encapsulated in steel canisters. However since 1990, only a limited space is available in the clusters for these horizontal type groundbeds. All groundbeds installed since 1990 are completed with deepwell type groundbeds. The anode used is a high silicon-chromium-cast iron type of anode.

The Arun CP groundbeds have been designed for a 25-year life. However, some groundbeds have failed prematurely and others are expected to fail soon due to several specific reasons. The remaining useful life of the groundbeds can be forecast from the historical performance data, and from the anticipated CP current injection requirements. Forecasts of the remaining life of each groundbed is important for planning of future replacement requirements, and to assure sufficient future impressed CP current supply.

Up the end of 1994, a total of eighty four groundbeds were installed in Arun; fifty three horizontal and thirty one deepwell. MOI's experience indicated that horizontal groundbeds performed better than deepwell groundbeds. However, deepwell groundbeds will be used for future Arun CP groundbeds due to the limited available space.