A pilot scale study into the feasibility of applying magnesium anodes to the cathodic protection of well platforms and well casings, was carried out by Saudi Aramco in the offshore Safaniya field in the period of 1998-2000. There are currently 200 production platforms, covering area of 750 sq km, in which there is no power supply available for impressed current cathodic protection (ICCP).

The well platforms are protected by aluminum galvanic anodes. These galvanic anode systems are designed with a 25-year life expectancy, providing a minimum structure-to-water potential of -0.90 Volts with reference to a Ag/AgCI electrode.

Down-hole logs conducted with a Corrosion Protection Evaluation Tool (CPETTM) were run on several wells. This revealed influence of cathodic protection from the aluminum anodes through the shallow corrosive formations, down to an average depth of approximately 760 m (2,500 feet).

Thirty percent of the well casings have experienced leakages due to the presence of corrosive formations at depths between 760-1220m (2500-4000 feet). It was considered that the higher driving potential of 1.7 volts magnesium anodes might provide protective current down to these depths, resulting in cathodic protection of the well casing and preventing further failures.

A pilot study was performed on a platform in the Safaniya Field. Ten magnesium anodes were installed in a fan shaped formation on the seabed approximately 50 m (180 feet) from the structure. To minimize the effect of voltage drop, 2/0 AWG (70 mm2) cables were used to connect the anodes to the platform.

The actual consumption rate during the trial was determined to be approximately 1218 A-hrs/Kg, which is comparable to the theoretical value of 1100 A-hrs/kg given by the NACE Standard RP0176-94.

A CPET™ log was run down the well casing to determine the effects of the modular magnesium anodes. The results of the tests showed that influence of cathodic protection was achieved to a depth of 5,300 feet down the well casing, with the Modular Magnesium Anode System proven to have the required capacity and drive to achieve cathodic protection through the corrosive zone.