IMCA Marine Division

Publication Details

Reliability of Position Reference Systems for Deepwater Drilling

This study report, published in January 2001, compares the risk and reliability of position reference systems on DP drilling units with the expectations for position references when the rules for Class 2 and Class 3 were written, i.e. although the situation is degraded when the DGPS does not function due to ionospheric interference, is it degraded to an unacceptable extent?

Specifically, the study's main aims were:

• to facilitate an industry consensus with respect to position references in deep and shallow water in terms of safety, reliability and the consequences of loss of position;
• to enable the update of industry guidance to reflect the consensus, without degrading the levels of perceived safety already agreed and used in shallow water;
• to promote any changes made and facilitate their acceptance by regulatory bodies.

This extensive report contains the following chapters:

1. Introduction
2. Guidelines and Requirements
3. Fault Tree Analysis
4. Conclusions and Recommendations
5. References

along with extensive appendices, containing the data and specific analysis on which the study was based:

• Shallow water diving fault tree models
• Shallow water diving failure data
• Deepwater drilling fault tree models
• Deepwater drilling failure data
• Model result matrix
• Emergency disconnection analysis