The paper deals with design criteria which enable to adopt rational solutions when designing oil-and-gas field platforms meant to be operated under action of ice, wave and wind loads in regions with high seismic activity. It presents an approach for designing such facilities and designs of offshore ice-resistant platforms for oil-and-gas production.
At present Russia actively explores and develops its offshore oiland- gas fields. A specific feature of Russian shelf is severe naturaland- climatic conditions and complex hydrological nature of seas in areas of hydrocarbon deposits. Most important are wave, ice and seismic conditions that requires a special approach and architectural-and-structural solutions when designing facilities for the above regions.
A lot of offshore facilities installed on seabed are known (Mirzoev 1992: Dowson 1986; API RP 2T 1997) such as gravity type- held on soil by ballast, pilled- on pile foundation, and pileand- gravity type. Continuous structures (steel or reinforced concrete) constructed of floors, which form a tight contour, positively withstand action of ice fields transferring their forces to soil. However, if sea depth is more than 60–80 m, platforms of such type become bulky and metal-consuming, and their cost increases as a function of depth in the third power. In addition, a larger amount of ballast is required to provide the stability of gravity platforms in seismic regions, that along with increase in pressure caused by ice loads can result in an unacceptable collapse pressure on soil. It is also obvious that platforms with supports on seabed are not reliable under conditions of high seismicity. Much less sensitive to seismic action are platforms on floating base with tension links anchored by gravity anchors or pile anchors.
