Pipe Soil Interaction For A Buried Offshore Pipeline

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Introduction A problem that has been encountered by the oil industry in offshore operations is the large movement of pipelines. This movement may result in the parting of the line. There have been reports of many damaged pipelines following storms in the Gulf of Mexico. The aim of the research program described in this paper is to develop design criteria to allow offshore pipelines to be constructed in such a manner pipelines to be constructed in such a manner that movements will not occur, but that the pipeline will be stable over a long time. pipeline will be stable over a long time. To develop design criteria so that the stability of a pipeline can be assured, it is necessary to have an understanding of the manner in which a pipeline interacts with the supporting soil. This interaction is affected by many parameters. Some of these parameters are the size and weight of the line, the character of the soil, the method of the installation of the line, the kind of fluids pumped through the line, the temperature pumped through the line, the temperature variation of the line, the possible vibration of the line, the currents in the water at the ocean floor, the initial tension in the line, the possible upward flow of water in the vicinity of the line, the geometry of the line, the geology of the area and depositional environment, [possibility of submarine flowslides] and the possible scour or sedimentation at the ocean floor. While it obviously will be very difficult to evaluate the influence of some of the above parameters, it is thought that research should lead to a generally good understanding of the interaction between the pipeline and the supporting soil and, hopefully, to a rational design procedure. THEORY CONCERNING VERTICAL STABILITY Much study has been given to the design of pipelines for marshy areas or offshore pipelines for marshy areas or offshore locations; however, it is apparent that some confusion exists in regard to certain design parameters. In this discussion, the equilibrium parameters. In this discussion, the equilibrium under static conditions of a submerged pipeline will be considered. Fig. 1 shows a cylinder immersed in water and assumed to be motionless. The cylinder is also assumed to be very long so that a two-dimensional analysis is valid. The stability of the cylinder can be studied by considering the forces acting on it. These forces are the weight of the cylinder and the resultant of the water pressure on the cylinder boundary. The weight of the cylinder is wL where w = weight per unit length, and L = length of cylinder under consideration. The horizontal forces exerted on the cylinder by the water evidently add up to zero and are not shown.