Commercial development of the Sleipner field began in 1986 in two development stages:
Sleipner Øst (East) was brought into operation in1993, followed by Sleipner Vest (West) which started production in September 1996.
The Sleipner Production Licence, located offshore Norway in the North Sea Blocks 15/6 and 15/9, is operated by Statoil ASA with the following Licence partners:
• Statoil 58.34%
• ExxonMobil E&P Norway 32.23 %
• Total E&P Norge 9.41 %
This field was discovered in 1974 and production of gas and condensate (light oil) began in August 1996. The gas is exported in Norway’s transport network for sales gas, while condensate is carried in the pipeline to the Kårstø processing plant north of Stavanger. Condensate is exported from Kårstø by ship.
The Sleipner West Gas Field is tied back to the Sleipner East Gas Field, and the two fields share the same operations organisation. The Sleipner West development embraces the B wellhead platform on the field, and the T platform
gas treatment installation, which is linked by a bridge to the Sleipner A platform (at Sleipner East). Sleipner B is unstaffed in normal operation, and remotely controlled from the A platform. The unprocessed well stream (gas with up to 9% CO2) from Sleipner B is piped 12 kilometres to Sleipner T. Carbon dioxide is removed from the well stream on the T platform and injected back into the Utsira (saline aquifer) Formation.
The extra capital investment costs in connection with the capture, compression and injection of carbon dioxide amounted to about USD 300 million. The CO2 injection operational costs are integrated with the gas production (Opex) and not easily isolated, but are in any case relatively minor.
In order to monitor the performance and long-term integrity of this storage site a comprehensive geophysical monitoring programme has been developed and executed. Early proposals to install monitoring wells and down-hole tools were rejected on the grounds of the high cost and risks associated with drilling and well operations. The geophysical options have, however, proved both cost effective and immensely valuable. The geophysical monitoring dataset, to date, comprised a baseline seismic survey and 7 repeat seismic surveys, a baseline gravity survey and 2 repeat gravity surveys, and 1 electromagnetic survey. The time-lapse (4D) seismic data has been particularly valuable in monitoring the growth of
the CO2 plume in the subsurface. These monitoring data have been extensively studied and used as a basis for developing and refining quantitative CO2 monitoring and verification tools.