Design considerations for the safety of exposed submarine pipelines

The extension of pipelining operations to water depths greater than 200 feet has greatly compounded problems with pipeline installation and stability under storm conditions. Current technology limits pipeline burial to water depths of less than 200 feet, while ocean wave and current forces are known to be significant at these and greater depths. Present and future offshore exploration will require safe pipelines in water depths in excess of 1,200 feet. This study analyzes the environmental, soil, and pipeline stability factors which must be taken into account in these deeper water pipeline projects. Before the stability of an offshore pipeline can be determined, the effects of environmental extremes on the pipeline must be considered. This study presents a review of the pertinent wave equations and an analysis of pipeline settlement due to present pipelaying techniques. A computational procedure is presented which makes possible a comprehensive analysis of the overall pipeline stability problem. This procedure allows for the optimization of pipeline specific gravity as a function of pipelaying and environmental factors effecting larger diameter pipelines laid in deeper waters with existing equipment.