Risk analyses have been performed for several North Sea petroleum production platforms. A typical model platform considered in this paper is an integrated drilling, production and living quarter installation.
Different risk analysis techniques including fault tree and event tree have been used.
Some results of the analyses are presented as relative frequencies of different classes of accidents (number of fatalities and different sizes of oil spills)
Although the quantification of risk involves considerable uncertainties, relative importance of the different risk contributing factors can be established with reasonable confidence.
The risk analyses gave valuable insight into the accident mechanisms, giving rise to improved designs and operational procedures.
North Sea petroleum production does not involve hazards which are completely new to the industry. The isolated locations, the' environment and the increased physical sizes, however, bring new and somewhat unknown dimensions into the risk picture which prevents simple extrapolation of statistical data and experience from other areas. The installations must be fully self-supporting units, both under normal operation and during emergencies. This requires many utility functions in addition to the production and process systems with associated control and safety systems. With the limited space available, this makes such a platform complex, although each system, function and activity in itself is simple in principle and based on well known industrial practice.
This paper is based on extensive studies which, to the knowledge of the participating organizations, as not been carried through previously to such degree of detail and completeness.
Analytical methods were not readily available for the performance of such complete analyses. Therefore some developments in the analytical approach had to be made. Some input data and relevant technical information were difficult to obtain and sometimes non-existent, and parts of the work had to be based on estimates and engineering judgments.
The main Objectives of-the performed risk analysis projects have been:
to gain experience with the risk analysis approach to a complex system like an integrated offshore platform, and further develop the risk analysis method as an analytical tool for systematic safety evaluation of offshore platforms
to gain improved knowledge of the risk contributing factors for a typical oil and gas production platform in the North Sea
to estaa1ish a basis for possible improvements in future platform design, operation and maintenance
to achieve a better basis for documentation of risk and safety discussions with authorities.
Assessment of risk to human lives was of primary concern. In addition, the risks of large oil spill s have been considered, -while economic risks, - loss of production etc. were outside the scope of the present model study which has been limited to activities taking place on the platform. Risks associated with, for instance, helicopter transport in general, and other services external to the platform itself, have thus not been part of the study.
The risks considered are those present during the operational phases of the plant life. Construction and installation activities are thus not included.