Aker BP, operator of production license 203, and its partners are considering tie-back of its Gekko oil and gas discovery well (25/4-3) in the North Sea to the Alvheim floating production, storage, and offloading vessel after drilling two appraisal wells about 5 km east of Volund field and 200 km northwest of Stavanger.

Well 25/4-13 S south on the structure encountered a 43-m oil and gas column in the Paleocene Heimdal formation, of which 6½ m was oil. Nearly the entire interval consists of reservoir sandstones with very good to excellent reservoir quality. The gas-oil contact and the oil-water contact were encountered at 2,100 m and 2,106½ m total respective vertical depths subsea.

Well 25/4-13 A north on the structure encountered a 30-m oil and gas column in the formation, of which 6 m was oil column. About 15 m is net reservoir sandstone with very good to excellent reservoir quality. The thickness of the oil zone is somewhat uncertain due to reservoir quality variations.

The objective of the wells was to prove a possible thicker oil column in the Heimdal formation than previously proven in the Gekko and 25/4-8 wells, and to gather more information about the complexity of the reservoir.

The discovery was proven in Paleocene reservoir rocks (Heimdal formation) in 1974. Prior to the appraisal wells, the operator’s resource estimate for the discovery was 4.9 million standard cu m of oil equivalent/day of recoverable oil.

Preliminary estimates place the size of the discovery between 0.9 and 2.3 million standard cu m/day of recoverable oil and 3.8-6.3 billion standard cu m/day of recoverable gas.

Appraisal wells 25/4-13 S and 25/4-13 A were drilled to respective vertical depths of 2,153 m and 2,159 m subsea, and respective measured depths of 2,653 m and 2,641 m subsea. The wells were terminated in the Paleocene Heimdal formation. Water depth at the site is 120 m.

Aker BP said extensive data acquisition and sampling have been carried out, but the wells were not formation-tested.

PL 203 was awarded in 1996, and these wells are the fourteenth and fifteenth exploration wells drilled.

Both wells have been permanently plugged. Both wells were drilled using Odfjell Drilling’s Deepsea Stavanger semisubmersible drilling rig. The rig will now leave the Norwegian Continental Shelf to drill wells for Total SA.

Source: Oil & Gas Journal