As the global need for oil products increases and most of the natural inland oil resources are being depleted, the oil industry is seeking to explore offshore mineral and oil deposit areas in deep water. Offshore oil and gas production represents between fifteen and twenty percent of the total production of oil and gas in the world today. The feasibility of such exploration and production depends greatly on the current technological capabilities. Depths of up to 1500 ft. have already been attained and plans for drilling to 6000 ft are underway. Most recently, in the United States, the oil production potential was explored in the Baltimore canyon (5000 ft.) as well as in the East Coast Outer Continental Shelf leases off the Gulf of Mexico (3000 ft.) Abroad, exploration has been undertaken in the ultra deep waters off the Shetland Islands of the United Kingdom and Newfoundland, Canada (4500 ft.) Such offshore projects point out the need to look into the new array of problems associated with structures and operations in ever increasing water depths.
One of these problems may occur during the process of laying a pipeline on the seafloor. It is known as the propagating buckle. This physical phenomenon starts as a local substantial deformation of the cylindrical pipeline and turns into a buckle that spreads in the longitudinal direction, flattening the pipe in its path. In the course of laying, a number of occurrences may cause local damage of the pipe. Kinking and excessive bending at the sag is very likely and very difficult to overcome. Likewise a dent may form while the pipe is still on the barge, as a direct result of the accidental mishandling of a pipe segment. The external pressure in deep water may exceed the lowest pressure at which a propagating buckle can occur. Thus the laying of pipelines requires modifications in both the installation equipment and the procedures as well as the design criteria, on the basis of experimental and analytical results. In the last two decades, the propagating buckle has been the subject of several studies which have led to better understanding of the phenomenon.
In this study a finite element technique is developed for the analysis of propagating buckles in deep-water pipelines accounting for large deformation, elastoplastic material behavior and contact between regions of the interior wall of the pipe.
Related Publications: Katsounas, A.T., Song, H.-W. and Tassoulas, J.L., “Finite Element Analysis of Propagating Buckles in Deep-Water Pipelines,” Paper No. 6413, Proceedings, Offshore Technology Conference, Houston, Texas, May 7-10, 1990.