Energy Efficient Operation of Gas Export Systems

The gas transport system on the Norwegian continental shelf (NCS) consists of 7 800 km of pipelines and is the largest offshore network of its kind in the world. Natural gas is processed at treatment plants in Norway, and dry gas exported through pipelines to customers in the UK and continental Europe. These customers have the opportunity to make varying gas delivery nominations, and meeting such sales gas commitments is important. A major challenge is to operate the network at minimum cost, with minimum environmental emissions, fulfilling variations in contractual nominations and maintaining a sufficient pipeline inventory to provide operational flexibility. Optimum pipeline inventory and optimum operation of export compressors have been analysed in earlier studies. The scope of the work presented in this paper is to establish a model for optimum operation of a gas export system, including customer nominations and operation of pipelines and compressor stations. That implies improving system energy efficiency, reducing environmental emissions and maintaining sufficient availability and export deliverability . The model will provide guidelines which will be implemented in planning and operation of the gas export system. This model is based on analyses of operational data from the gas export system on the NCS. The data are analysed using statistical and simulation software. The paper describes the established model for optimum operation of the system, where specific power consumption is minimised. A case study which illustrates the use of the model is also presented. Furthermore, the paper reports on a cost-benefit analysis based on the established model.