Selection of Power From Shore for offshore Oil and Gas developments

Abstract

Abstract With a step out distance of 170 km and a design power of 55MW, Martin Linge offshore gas field, will be the longest AC submarine cable power supplying an entire offshore Oil and Gas platform from the shore. This field development comprises a platform with a jack up rig and a Floating Storage Offloading unit. This paper discusses the criteria to consider and select a power from shore concept instead of an offshore Gas Turbine power plant which is the current practice in the offshore Oil and Gas industry. Since in a first approach, for such long step-out distance, the choice of power from shore would be to select a DC transmission line, the paper discusses the design and the main technical challenges of this long step-out AC transmission development. Finally, the system approach, required for the development of the onshore and offshore part of the project, is described. Introduction Discovered in 1975, Martin Linge offshore gas field (formerly named Hild) and located in the North Sea will be operated by Total Norge which has chosen to base this development with a power from shore concept. The facility will be designed for remote control from Total Norge onshore base in Stavanger (Norway). The field will be developed with a subsea installation and topside facilities. The processed gas will be exported to Total St Fergus terminal in UK via a new link to the existing Frigg UK Pipeline (FUKA). The oil, water and condensates will be processed and stored on a dedicated FSO storage vessel where water will be separated for reinjection, and oil will be exported via shuttle tankers. With a step out distance of 161km and a design power of 55MW, this will be the world's longest AC submarine cable power supplying an entire offshore Oil and Gas platform from the shore. This paper discusses the criteria which have been considered to select a power from shore concept instead of an offshore Gas Turbine power plant which is the current practice in the offshore Oil and Gas industry. Since in a first approach, for such long step-out distance, the choice of power from shore would be to select a DC transmission line, the paper discusses also the design and the main technical challenges of this long step-out AC transmission development. Finally, the paper underlines the electrical design particularities of this development and gives an operator's viewpoint as to the way forward. Project presentation The Martin Linge Field (formerly named Hild), is located on the Norwegian Continental Shelf, 75 km North of Frigg, 42 km West of Oseberg, 87 km North-East of Bruce, and 38 km South-East of Alwyn North field. TOTAL E&P Norge is the operator (49%) with Petoro (30%) and Statoil (21%) as partners. The Martin Linge field is one of the largest un-developed gas discoveries in the North Sea. Discovered 30 years ago, and operated today by Total E&P Norge AS, the field consists of several faulted and segmented gas condensate accumulations in the mid-Jurassic Brent group. The field also includes the Frigg oil reservoir which is a viscous, thin oil accumulation overlain by a small gas cap. Production is expected to be ~ 100 kboepd peak after start-up in quarter 2016, with ~ 70 kboepd during gas plateau. The total reserves are expected to be 176 Mboe. The production drive mechanism for the Hild (Brent) wells will be pressure depletion, i.e. no injection wells are planned for reservoir pressure maintenance. Frigg oil wells will be artificially lifted with gas lift. The produced water will be re-injected into the Frigg reservoir aquifer (not needed for pressure support).