The safe and economic design and operation of offshore structures often depends on the accurate assessment of the extreme and normally occurring environmental loads. The present paper describes a series of generally applicable modeling techniques and demonstrates their use for establishing environmental design criteria off Peninsular Malaysia.
Petronas Carigali Sdn. Bhd. is presently developing the Dulang Oil Field, located in the South China Sea (5 50'30'N, 104 07'30"E) some 130 km to the east of Peninsular Malaysia.
The present paper deals with a study aimed at establishing environmental criteria for the design of jackets, risers, topsides, pipelines and tanker mooring arrangements in this area. The study dealt with the assessment of criteria for the impact of wind, wave, current, water level, marine growth, humidity, visibility, temperature, rainfall, sunshine, and corrosivity.
The study was carried out by the Danish Hydraulic Institute (DHI) which in turn made use of the expertise of Ocean weather Inc. for the specification wind fields of historical storms, the Danish Water Quality Institute for the assessment of the potential for marine growth, and the Danish Corrosion Centre for establishing recommendations for corrosion protection.
The study was carried out and documented in May-July 1984. The essential outcome of study was directed into a separate document which was tailored to meet the requirements of the design offices. The time-effective schedule benefited from earlier relevant and site-specific experience held by DHI and Ocean weather Inc. and from the close co-operation between all involved parties.
The study was organized so as to direct most effort into the assessment of wind, wave, current and water level conditions. Design criteria for these environmental conditions were established primarily by making use of modeling techniques in the hindcast mode, i.e. these techniques were used to represent the past events of most interest. Design criteria for other environmental conditions were established primarily by reviewing already available information. The present paper describes that of the part of the study which made use of hindcast techniques.
The project area is in a monsoon region. A regular, seasonal variation of the atmospheric pressure distribution over the South china Sea causes correspondingly regular, seasonal winds. Winds between north and east are predominant during the winter season. Winds between south and west are predominant during the summer season.
Gales are infrequent in this part of the South China Sea. When gales do occur, they are normally caused by a temporary intensification of the monsoon winds. Very infrequently, violent gales may be experienced in association with tropical storms. The intense tropical depressions, which are termed typhoons, in general originate from tropical waters far to the east of Peninsular Malaysia. Only at very rare occasions have they come close to the project area
