The Spar Platform: A Design That Transformed Deepwater Development

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 30709, “The Spar Platform: Transforming Deepwater Development,” by Anil Kumar Sablok and Tim Otis Weaver, TechnipFMC/Genesis, and John Edwin Halkyard, Deep Reach Technology, prepared for the 2020 Offshore Technology Conference, originally scheduled to be held in Houston, 4-7 May. The paper has not been peer reviewed. Copyright 2020 Offshore Technology Conference. Reproduced by permission. The spar is the only successful dry-tree solution for deepwater production that can operate successfully in the deepest fields and the most severe environments. Its deep draft results in natural periods outside the range of waves, which has led to its wide acceptance for different field scenarios. The complete paper is an extensive review of the evolution of spar designs, focusing on the progression of work that ultimately led to the application of a transformative concept to the oil industry. Introduction The spar can support a drilling rig as well as top-tensioned production risers in water depths thousands of feet greater than the water depth limit for a tension-leg platform (TLP). It is especially well equipped to support steel catenary risers (SCRs) using the pull-tube option, which allows the SCR to serve as a continuous welded steel containment for hydrocarbons from the seafloor to the topsides and protects the riser from vortex-induced vibration in the fastest part of the current profile. Broadly speaking, there are three configurations of spars: classic, truss, and cell, with the common feature being that the center of buoyancy is higher than center of gravity. Table 1 of the complete paper lists all oil and gas spar production platforms that have been installed at the time of writing, in chronological order of installation. The complete paper devotes several pages to the spar’s initial development, including the crucial role of Edward Horton, the inventor and designer behind the spar production and storage concept and the TLP, and some of his colleagues. Years of development and navigation of various design challenges culminated in the installation of the Neptune spar in 1996 on time and budget. After the installation and success of Neptune, several other classic-design spars were implemented. The riser system on the Neptune spar had two unique features: buoyancy cans provided the tension, and the riser passed through a point of high bending and potential wear at the keel. The keel joint was a straightforward design; a sleeve around the main riser pipe pro-vided wear protection and distributed the bending in the riser to two endpoints rather than at a single contact point.