Conditional monitoring and operational management of a subsea production system

Abstract

There is an identified need for mid-level systems for monitoring a large number of subsea wells. To meet this demand Statoil is looking into developing a software program for such monitoring. As a step in this process, this thesis is looking into development of key condition indicators to be used in such a program for the Statoil operated Gullfaks Satellites tied back to Gullfaks C (GFCSAT). The indicators developed in this thesis are aimed at contributing to a good and efficient mid-level monitoring of technical integrity and availability for the GFCSAT subsea production system.

The first step in the development process has been to establish the goals and objectives that will be the pillars for the indicators. These goals are based on the same goals that are used to govern the operations of the GFCSAT; the three chosen goals are within the areas health, safety and environment, operational costs and production. For each of these three goals relevant reports of past events were retrieved from GFCSAT historical records. The reports were categorized into 11 categories based primarily on common failure modes. Categories without indicator detectable failure modes were discarded after the analysis process leaving 8 categories for further analysis. For the indicator detectable failure modes possible indicators were suggested and reviewed using a checklist approach. Based on this review, one indicator was selected for each of the 8 categories. The 8 selected category indicators were in turn compared based on the number and severity of reports, trends and coverage of the failure modes within the respective category. Based on this the key condition indicators are found to be the indicators within the categories communication, hydraulics, sensors, downhole gauges and multiphase meter. The hydraulics-indicator is a system indicator aimed at detecting leaks. The other four indicators are well specific and are all aimed at detecting the failure modes no signal and out of range signal for the equipment within the respective categories.