| dc.description.abstract | Oil and gas exploration on the Norwegian Continental Shelf has been going on since the 1960. Many smaller oil fields have been found and at that stage they have not been developed, because alone they have not been economically recoverable with the technology of that day. The Gullfaks field started to produce in 1986 and when the subsea concept was developed, the nearby oilfield Gullfaks South was developed as a subsea solution in 1998, tied-in to the Gullfaks A platform. Low production rates and newer 4-D seismic surveys of the Gullfaks South field showed that the recoverable oil from this field was only 8%. This was the key driver for the new development, the GSO, Gullfaks South Oil. The GSO project shall increase the recovery rate by developing the field with 2 new subsea templates that includes four production wells and two gas injection wells.
The Gullfaks Oil field is already developed with six templates including flowlines that have been producing since 1998. Some of the existing infrastructure shall be re-used due to the existing templates are at their end of production lifetime. Lack of spare J-tubes for new risers on the Gullfaks A supports the decision of re-using existing infrastructure. The production template, the O-template, shall be tied-in to existing flowlines. By re-using these flowlines the cost of the development will be reduced, but limitations will be given due to fixed diameters on the flowlines. The O-template shall have one 8” and one 6” flowline, these are within the design criteria of material stresses based on the reservoir properties and ambient environmental properties. Arrival pressures on the platform, from the template are within the limitations of the process pressure at 56 bars for the 8” throughout the whole production lifetime. The 6” shall co-produce with other wells, this is only analysed to this point where they start to co-produce. The injection template, the P-template will have an extended flowline from another injection template, this will provide necessary reservoir stimulation for the GSO.
The production flowlines, the 6” and 8” are analysed for flow assurance challenges. Flow assurance is a very important design requirement for subsea flowlines. It is important to understand how and why they occur to be able to mitigate them. It is essential to keep good flow assurance for a subsea development, and necessary to understand how to both avoid them and to get out off flow assurance challenges in a safe matter. The challenges found are manageable with the chosen measures. The analyses are done with the basis in the production profile and the ambient surroundings. The 6” and 8” flowlines are not redundant, but a supplement to each other during the whole production lifetime. The 6” is suitable in the beginning and end of the production life, the 8” is the best option in the middle part of the production lifetime.
The GSO development is a sensible development to increase the recovery rate at the Gullfaks South oil field. | nb_NO |
