TABLE OF CONTENTS One of the recent developments in the offshore petroleum industry is that floating production facilities and subsea production systems are taking over more and more from surface installed facilities. Subsea production systems also implicitly make use of floating installations, typically mobile drillings units.
This is the main background for an increased focus on risk due to possible failures of marine systems i. e., systems such as ballast systems, anchoring systems, loss of buoyancy, weight control as well as structural and hull systems. Risk modelling for these systems is discussed in this chapter.
It is 25 years since serious accidents or incidents associated with loss of buoyancy or stability occurred in the Norwegian sector. But there have been incidents and accidents in other areas, which remind us that this hazard has not been eliminated. The most serious accident ever in this category was the capsize and total loss of semi-submersible drilling unit Ocean Ranger in 1982 off Newfoundland.
The regulatory requirements discussed here are those applicable to analysis of reliability, vulnerability and risk associated with loss of buoyancy and stability.
There are requirements for the design of ballast systems and for the stability of floating units. The requirements for probabilistic/risk analysis of these systems are somewhat indirect. The survivability of the units is included in the phrase 'main support structure', which in the facilities regulations (PSA, 2002a) Section 6 is defined as a Main Safety Function. The facilities regulations...
