Wintershall Norge AS, operator of production licence 248 F, is in the process of completing the drilling of four wells in the North Sea.

The wells are wildcat well 35/11-20 S, appraisal well 35/11-20 A and wildcat well 35/11-20 B. Due to technical issues, well 35/11-19 S had to be abandoned, and well 35/11-20 S was drilled about 50 m southwest of 35/11-19 S.

Well 35/11-20 A was classified as a wildcat well, but will now be reclassified as an appraisal well.

The wells were drilled about five km southeast of the Vega field in the North Sea and 100 km southwest of Florø.

The primary and secondary exploration targets for well 35/11-20 S were to prove petroleum in Late Jurassic reservoir rocks (intra Heather formation sandstone).

The well did not encounter reservoir rocks in the primary exploration target. The well encountered an 8 m oil column in the secondary exploration target at the top of an intra Heather formation sandstone with poor reservoir quality and a total thickness of about 70 m.

Objective

The objective of well 35/11-20 A was to delineate the oil discovery in intra Heather formation sandstone, and to prove petroleum in Middle Jurassic (Brent group) and Early Jurassic (Cook formation) reservoir rocks.

The well encountered a total oil column of 33 m in intra Heather formation sandstone, of which 19 m were of good reservoir quality. Due to technical issues, it was not possible to reach the Brent group and Cook formation.

Well 35/11-20 B was drilled to further delineate the oil discovery in intra Heather formation sandstone. The secondary target was to prove petroleum in Middle Jurassic (Brent group) and Early Jurassic (Cook formation) reservoir rocks.

The well encountered a total oil column of 46 m in intra Heather formation sandstone, of which 29 m were of moderate reservoir quality. A total oil column of 19 m was encountered in the Tarbert formation in the Brent group, of which 10 m were of moderate reservoir quality. The Cook formation was encountered with a total thickness of about 170 m with predominantly poor reservoir quality and only traces of petroleum.

Estimates

Preliminary estimates place the size of the discovery between 1.5 and 4.5 million m3 of recoverable oil equivalents. The licensees will evaluate the discovery along with other nearby discoveries with a view toward a potential development.

The wells have not been formation-tested, but extensive data and samples were collected. The wells are the second, third, fourth and fifth exploration wells in production licence 248 F.

Wells 35/11-20 S and 35/11-20 A were drilled to respective measured depths of 3553 and 3943 m below the sea surface and respective vertical depths of 3437 and 3293 m below the sea surface. Both wells were terminated in the Heather formation in the Middle Jurassic.

Well 35/11-20 B was drilled to measured and vertical depths of 5083 m and 4055 m below the sea surface, respectively, and was terminated in the Statfjord group in the Early Jurassic.

Water depth at the site is 373 m. The wells will now be permanently plugged and abandoned.

Wells 35/11-19 S, 35/11-20 S, 35/11-20 A and 35/11-20 B were drilled by the Borgland Dolphin drilling facility.

Source: Energy Global