| Abstrakt: |
Rising development costs for new oil and gas facilities has led many operators to look to maximise the production capability from existing onshore and offshore plants. These projects often include a combination of brownfield and greenfield development - with the target of using as much of the existing infrastructure as possible. For example, as existing wells become depleted, production tails off, and new wells must be drilled for production, water injection or gas lift. Often this requires new wellhead platforms because existing well slots are fully utilised, or they are required to enable drilling to reach other untapped parts of the reservoir. These type of projects present many challenges, especially when the original facilities were designed and built in the mid 1990's in a low oil price market, when the CRINE initiative was hatched. This typically led to minimising facility flexibility and stripping out any allowance for future expansion in order to reduce CAPEX. Many were originally designed for a limited lifetime, and now some of these facilities are the ones being extended and expanded to provide additional production throughput. This paper examines some of the electrical power system challenges during the expansion of one such offshore facility in Denmark. A series of developments over the years had already seen the peak load increase beyond the rating of one of the 2 × 100% rated main generators. The latest plans involved significant changes to the gas compression system, including new compressor bundles, requiring new and larger rating of electric motors and gearboxes. Further additional loads and switchgear would also be added with two new wellhead platforms, one bridge linked and the other 2.5km away from the host platform. The paper considers the required motor starting constraints at the limits of the power system capability, switchgear very close to its maximum fault rating, and weight and space constraints. The methods used to evaluate and overcome some of these issues will be presented. This includes the use of detailed electrical power system modeling as a tool to simulate transient conditions of the existing and revised power distribution system, and actual transient power measurements to verify the model results. Details of the motor design requirements, with extremely constrained maximum starting currents, and modifications to the main generator AVR's will be discussed. Finally, some feedback from the installation/commissioning phase of the project will be given as lessons learnt for the benefit of other similar brownfield projects. [ABSTRACT FROM PUBLISHER] |
