Condition based maintenance for well access systems

Abstract

Number of intervention operations in subsea wells has been increasing last years. During the intervention operations workover and completion risers are subjected to large environmental loads. Intervention operations are mainly guided by the operational analysis report, though the reports are generated by a computation which is based on conservative standards. Therefore interventions were carried in smaller operational windows than actual. Failure of subsea intervention equipment can be highly critical and wait on weather time can escalate operation cost substantially. It is due to uncertainties and misjudgments lied under operational analysis. Monitoring techniques can be used for measuring actual state of the workover risers. Data from this monitoring helps for better understanding operational situation and to make better decisions. By doing real-time monitoring companies can operate in larger operational window and make better planning for maintenance. There are not many companies who is practicing riser monitoring and there is not direct guidance for implementation of riser monitoring system in international standards. In this thesis traditional operation guidance and industrial riser monitoring experiences were presented. Methodology for implementation of riser management system with emphasis on implementation of riser monitoring was created. Process of riser monitoring implementation is described in several steps starting from defining equipment selection and finishing how information presented to the operator. Application of the methodology is illustrated in case study, where riser monitoring system implemented for open sea workover riser.