Maintaining effective cathodic protection for offshore facilities poses a challenging task for operators with ageing assets. Cathodic protection can be characterised by the reduction of the corrosion rate on metal surfaces that are continuously exposed to seawater and sediments via electrochemical protection. Integrity management of these cathodic protection systems is vital as facilities begin to reach their intended design life and operators look for life extension options.
An oil field consisting of a number of well head platforms, a living quarter platform, a flare platform and a processing platform were required to be re-qualified and investigated for possible life extension measures. The cathodic protection assessment for these platforms is the focus of this paper, where the assessment process was critical in assuring the long term integrity.
To guarantee the integrity of the facilities, a methodology that incorporated initial calculations based on mass and current requirements in conjunction with calibration calculations, factoring in present conditions of the facilities, were developed to predict the integrity of the systems for re-qualification and life extension. This paper documents the initial cathodic protection assessment methodology as well as the calibration methodology used to assess each facility for re-qualification and life extension. The calibration calculations were developed to verify the cathodic protection based on measured /observed values rather than assumed design values recommended in the relevant standards and used in the initial cathodic protection calculations.
The paper also provides an overview of the cathodic protection assessment for these offshore facilities in relation to the integrity management for life extension and mitigation options. This overview details the finding in regards to developing a successful cathodic protection program that can be managed and evaluated accurately to allow for prolonged design lives for offshore facilities.