High Level Corrosion Risk Assessment Methodology For Oil & Gas Production Systems

Assessing corrosion risks and developing appropriate inspection and mitigation measures forms a vital part of Asset Integrity Management (AIM) for operating any ageing asset.  However, for many systems detailed information is often scarce and/or unreliable, which prevents or limits the application of many Risk Based Inspection (RBI) databases / software systems, which are “data hungry”.  In order to overcome this limitation, and to allow corrosion risk assessment of both existing and aging facilities, an in-house methodology has been developed.

The system is based on industry standards and follows the UK Heath & Safety Executive (HSE) Corrosion Management Guidelines.  The method assesses a number of common degradation mechanisms and has the flexibility to incorporate additional mechanisms as required.  A key aspect of the approach is that it can be applied either as a paper exercise or run as a semi-automated assessment within a standard spreadsheet or database application, on both “corrosion circuits” and vessels. The flexibility of the system enables it to be integrated into existing Management Systems and linked to failure and anomaly databases as appropriate.

The system is designed to accept a range of data inputs including “engineering judgement”, summary of inspection data, monitoring data, predicted corrosion rates, etc as may be available; overcoming problems with sparse / non-existent data, whilst still providing a logical, transparent and fully auditable system for later review, update and modification as may be necessary.

The system can be used to drive the development of corrosion monitoring, fluid sampling and inspection plans (Written Schemes of Examination (WSE)) for process plant.  When run within a database application the development of the inspection plans is semi-automated and enables inspection techniques and locations to be defined based on inspection data and corrosion risks for individual vessels and corrosion circuits.  Regular synchronisation between the two analysis “engines” ensure that the most up to date information is used to generate the inspection plans.

The use of the combined corrosion risk assessment methodology and automated Inspection plan development, avoids the need for labour intensive inspection driven integrity management systems where data or resources are not available. 

The overall system will be described together with examples of application to both ageing and new facilities.