ABSTRACT

The Statpipe gas transmission system comprises totally 880 km offshore pipelines and an onshore NGL fractionation-plant. Gas from several fields located in the North Sea are transported in the system to buyers on the European Continent. Part of the gas is transported in dense phase to the NGL-plant for processing to sales gas and NGL products specifications. The gas transport through the system is monitored and controlled from a Pipeline Control Centre (PCC) located in Norway. There is implemented a real time simulator in the PCC SCADA-computer. SCADA data are used as boundary conditions for solving the transient flow equations of the real time simulator. In addition, several application programs are available for offline simulations. The present paper focus on operational use and experience with the real time simulator and applications programs.

The Statpipe System

The Statpipe system is a gas gathering and transmission system for transportation and treatment of gas from the Statfjord, Gullfaks and Heimdal fields in the North Sea. It includes 880 kilometers of pipeline, two offshore riser platforms and an onshore terminal for gas treatment and NGL extraction. The system was put into operation in 1985. Figure 1 shows the main dimensions and lengths. Associated rich gas is transported from the Gullfaks and Statfjord oil fields to the Kårstø NGL plant. The rich gas is transported in dense phase, i.e. at pressures higher than the cricondenbar (see figure 2). Typical operating pressures are in the range 120 to 167 barg. Design pressure of the pipeline is 172 barg. At Kårstø the heavier components of the rich gas is separated and fractionated into propane, normal-butane, iso-butane and natural gasoline. These products are stored in tanks and shipped from the gas terminal. The dry gas, mainly a mixture of methane and ethane, is sent through a pipeline to the riser platform 16/11S. At this platform the dry gas pipeline from the Heimdal field ties in, and the mixed gas is moving further to the Ekofisk Centre via riser platform 2/4S. From there on, the gas is transported in the Norpipe system to Emden in Germany, and distributed to consumers in Germany, The Netherlands, Belgium, France and Austria. The operational pressure range for the dry gas system is 60 to 116 barg. By installing additional compression facilities, the transport capacities can be increased. The design pressure for the Kårstø to 16/11S leg is 172 barg, and the Heimdal to 16/11S leg and 16/11S to 2/4S leg have design pressures of 156.8 barg.

Statpipe Coordination

The day to day operation of the Statpipe system is monitored and coordinated from a Pipeline Control Centre (PCC) at Karmøy, close to the Kårstø terminal, see figure 3. Information to/from the productions platforms, the gas terminal, the riser platforms and the Norpipe system operators are transferred via a telecommunication system to the control centre. This includes data, telex and voice traffic. The main goal of the operation is to meet the daily nominations of gas given by the buyers on the European Continent.

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