As an operator of a large submarine transport network Statoil is continuously seeking for improved condition assessment methods for the pipeline systems. In order to meet the overall operational objectives a risk-based philosophy has been introduced. This paper describes the principles behind the risk based condition assessment philosophy and how these principles are accounted for in the proposed assessment methodology. Failure modes with impact on the system structural integrity are discussed with respect to relevance for the operating phase and the possibility of detection during inspection. Condition assessment results are used for optimisation and planning of activities related to inspection, product monitoring and transport capacities, and for specification of corrective actions. Estimated risk and reliability parameters are used to optimise inspection activities with respect to priority of areas, selection of suitable equipment and determination of inspection intervals.
Large resources are used to safely operate offshore pipeline transport systems. In addition to the continuous product monitoring, this includes a wide range of inspection activities. The collected information is used to assess the actual pipeline condition and to predict any future development. Traditionally, inspection activities and the subsequent condition assessment have been done on a regular basis, regardless of the actual condition. Short inspection intervals have been selected in order to comply with recommendations given by the authorities, or because an increased inspection interval has not been properly documented. Inspection objectives have not been defined in detail for each separate system, but only adopted as general requirements. The condition assessment has been based on qualitative risk techniques, including a large degree of engineering judgement. During the last couple of decades risk principles have been introduced in the oil-industry as a tool for inspection and maintenance planning especially related to platform topside processing facilities.
