25/8-11

General

The 25/8-11 well was drilled in PL 027 with Esso as the operator and sole licensee. The well was drilled in the Ringhorn prospect, which is located approximately 14 km North of Balder. The primary target was the Paleocene Hermod Formation sandstones. Jurassic sandstones constituted a secondary target.

Operations and results

Wildcat well 25/8-11 was spudded with the semi-submersible drilling rig "West Alpha" on 16 October 1997 and drilled to a total depth of 1994 m in Early Jurassic sediments of the Statfjord Formation. The well was drilled with spud mud down to 1001 m and oil-based mud from 1001 m to TD. Hydrocarbons were encountered in both targets. Top Hermod sandstones were found at 1765 m. The Paleocene OWC (from wire line log) was found at 1775 m. The Paleocene reservoir properties were close to those of the Balder reservoirs and it was not the plan to test this reservoir. The top of the Jurassic reservoir (Top Statfjord Formation) came in at 1891 m. The Jurassic OWC (from wire line log) was found at 1935 m. The discovery in the Jurassic was the first of it's kind in this area and it was therefore decided to test this part of the Ringhorn Discovery. One core was cut in the interval 1763 m to 1790 m from lowermost Sele Formation and through half of the Hermod Formation. Two MDT samples were taken in the Statfjord Formation: one oil sample from 1919 m and one water sample from 1938 m. After production testing the well was suspended as an oil discovery on 2 December 1997.

Testing

A DST was performed in the interval 1892.5 m to 1909.5 m in thin sands of the Upper Statfjord Formation. The well produced 517 Sm3 oil per day and with a GOR of 42 Sm3/Sm3 on a 40/64th inch choke. Only surface samples were collected. Initial reservoir conditions at 1882 m were found to be 18.74 Mpa and 78 deg C. The plan was to continue with the test by perforating a lower sand interval and do a commingled test of both sand inte