Submarine Pipeline Installation JIP: Strength and Deformation Capacity of Pipes Passing Over the S-Lay Vessel Stinger

Abstract

The development of deep water gas fields using trunklines to carry the gas to the markets is sometime limited by the feasibility/economics of the construction phase. In particular there is a market for using S-lay vessels in water depth larger than 1000m. The S-lay feasibility depends on the applicable tension at the tensioner which is a function of water depth, stinger length and stinger curvature (for given stinger length by its curvature). This means that, without major vessel up-grading and to avoid too long stingers that are prone to damages caused by environmental loads, the application of larger stinger curvatures than presently allowed by current regulations/state of the art is needed. The work presented in this paper is a result of the project “Development of a Design Guideline for Submarine Pipeline Installation” sponsored by STATOIL and HYDRO. The technical activities are performed in co-operation by DNV, STATOIL and SNAMPROGETTI. The scope of the project is to produce a LRFD (Load Resistant Factor Design) design guideline to be used in the definition and application of design criteria for the laying phase e.g. to S and J-lay methods/equipment. The guideline covers D/t from 15 to 45 and applied strains over the overbend in excess of 0.5%. This paper addresses the failure modes relevant for combined high curvatures/strains, axial, external pressure and local forces due to roller over the stinger of an S-lay vessel and to sea bottom contacts, particularly: • Residual pipe ovality after laying, • Maximum strain and bending moment capacity. Analytical equations are proposed in accordance with DNV OS F101 philosophy and design format.

An apparatus design and testing of a flexible pipe-laying in submarine context

“…The flexible pipe (Huang et al, 2011) has many advantages as follows comparing with rigid pipe (Torselletti Enrico et al, 2006), first is better flexibility, second is fast fixing, third is good corrosion and compression capability resistance, fourth is low cost, thus, the laying the flexible pipe (Zhu, 2011) is paid high attention by the oil companies all the world. Flex-lay system is special equipment using oil pipelines under water (Qin and Zhao, 2010) and now the flexible pipe laying technology is grasped by big companies like HUISMAN.…”

Research on mechanical model for the J-lay method

“…These models have been improved gradually, but the final solutions are still very complex. Torselletti et al 16 analyzed the stresses of S-lay method on the suspended segment of pipeline based on the large deflection beam theory. Wang 17 put forward the Steel catenary risers (SCR) nonlinear mechanical model by applying the large deflection beam theory and obtained approximate analytic expressions using the homotopy analysis method.…”