Field development profitability is a function of many income and expense factors such as capital expenditures (CAPEX), operating expenditures (OPEX), production rate, product price, frequency of component failures and intervention vessel expenses. Component failures reduce the field total production rate and increase OPEX. The losses are directly drawn from the bottom line. Regardless of the chosen concept, the ability to efficiently keep production wells on stream is one of the most important factors determining field economic performance. A strategy on how to manage the Intervention, Maintenance and Repair (IMR) activities is therefore of utmost importance.

This paper describes the risk based approach used to develop the IMR strategy for the Ormen Lange field during FEED phase. The Ormen Lange field, the first deepwater discovery to be developed offshore Norway, is located 130 km from the West Coast of Norway at a depth of about 1000 meters. Developing Ormen Lange represents a major challenge with a combination of large water depth, extremely rough seabed conditions, long tie-back distance and demanding weather conditions. Fully developed the Ormen Lange production system potentially consists of 24 subsea wells and multiphase transport to an onshore terminal. This novel "Subsea to Land" concept was chosen in preference to a more traditional deepwater concept with an offshore processing facility with wet and dry wells (SPAR, TLP or SEMI) putting more emphasize on the management of reliability and maintainability of downhole, well and subsea equipment.

The paper illustrates how to estimate the cost associated with future unplanned interventions due to component failures (Risk Expenditures) - both direct intervention expenditures and the value of lost revenue - and how to assess the impact of different intervention strategies on overall life cycle economics. The link between high production volumes and intervention cost is quite straight forward - frequent and immediate interventions give high production volumes and evidently high intervention costs, while deferred/campaign interventions give lower intervention costs, and potentially lower production volumes. The challenge is to find the right balance. Findings regarding the effect of different interventions strategies, tooling and repair solutions are provided.

The benefits of the Ormen Lange approach are that improvement efforts are directed towards areas where the value yield is highest. It has put focus on critical equipment packages giving the highest contribution to Risk Expenditures, which subsequently has resulted in:

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    improved design/architecture to increase equipment reliability and/or

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    smarter and less expensive ways to fix the failed unit

The approach has also given a more transparent input to the budgeting process by providing an intervention cost breakdown on equipment level and a dynamic model to reflect the effect of improvement initiatives as the project moves forward.

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