Measured Behaviour of Platforms on the Norwegian Continental Shelf

Abstract

Full scale measurements are being conducted on fixed platforms according to the regulations issued by the Norwegian Petroleum Directorate on the collection of environmental and platform performance (E- and P-) data. This paper is mainly concerned with the quasi-static and dynamic behaviour of the platforms. First, a short description of the E-and P-data programme is given followed by some more detailed information on the particular instrumentation install led on typical platforms. Thereafter, the methods of analysis are described and, finally, samples of some of the results of the data analysis are presented and discussed. Only a limited amount of data has been analyzed, however, the results obtained so far indicate a fair correlation between the analytical models used in the design and the measured behaviour of the platforms. It should be noted that the techniques presently used for time series analysis all suffer from poor confidence levels, due to the short duration of the measured time series. However, more sophisticated methods for time series analysis have been proposed and they will be applied to the data in the future. INTRODUCTION The oil production industry in Norway has become a significant part of the industry. Much pioneering work has been done in the North Sea during the last fifteen years and there are still great challenges to be faced, in particular as the exploration and production move into deeper waters. In the areas where oil and gas have been found in sufficient quantities, production plants and living quarters are built on fixed platforms of steel and concrete. In this context the question of safety is vital. Regarding water depths and environmental conditions, experience of such large structures in areas comparable to the North Sea is very limited.

Structural health monitoring of civil infrastructure

“…With mandatory requirements for inspection (Det Norske Veritas 1977) and the expense and danger of diver inspection came a flurry of interest in vibrationbased diagnostic systems (Coppolino & Rubin 1980;Kenley & Dodds 1980;Shahrivar & Bouwkamp 1980;Brederode et al 1986). For example, environmental and platform performance (E-and P-) data (Spidsoe et al 1980) were collected, under the responsibility of the platform operator according to the requirements of the Norwegian Petroleum Directorate: 'in order to assess the safety of the load carrying structure of the platforms and their foundation'. The studies resulted in identification of dynamic characteristics and load-response mechanisms for a number of installations on the Norwegian continental shelf.…”

Comparison of three different methods of moments for derivation of probability distribution parameters

“…Despite these obstacles, it is of crucial importance to calculate the probability distribution of response as this information is the minimum requirement for efficient probabilistic analysis of offshore structures [8,9]. Previous work has shown that the Pierson-Holmes (P-H) distribution [10] is a reasonably good model for the global response of structures exposed to Morison wave loading when the effect of load intermittency on the response distribution is not severe [3,[11][12][13][14][15][16][17][18].…”