6507/7-12

General

Exploration well 6507/7-12 is located in the northern part of the Haltenbanken area, approximately 190 nautical miles west of the Norwegian coast. The block lies on the western flank of a series of NNE-SSW faults, which separate the Dønna Terrace from the Nordland Ridge/Trøndelag Platform to the east. The prospect is in the northern part of block 6507/7 and lies in an Early Cretaceous mini-basin developed in the hanging wall of the Revfallet Fault complex. The well was drilled to test a stratigraphic closure in an anticipated sand prone wedge of Albian age (Lower Cretaceous). The well was drilled in a location planned to test the minimum economic field size in terms of a tie-back to the Heidrun TLP. If hydrocarbons were present, the well would be tested through wire line logging and possible DST to determine hydrocarbon phase and deliverability. Secondary targets were in the Aptian, "Lange B" sands and in the Lysing Formation, also to be evaluated by drilling and wire line logging. Planned total depth for the well was ca. 20 meters into the Upper Jurassic Spekk Formation, prognosed at 3908 m RKB.

Operations and results

Exploration well 6507/7-12 was spudded on 17 July 1999 with the semi-submersible installation, "Mærsk Jutlander" and drilled to TD at 3976 m in the Late Jurassic Spekk Formation. The well was drilled with seawater and high viscosity sweeps down to 1316 m, with "BARASILC" water based silicate KCl mud from 1316 m to 2508 m, and with Baroid "Environmul& oil based mud from 2508 m to TD. Porous sands were encountered at all prospective intervals, at depths 70-80 m deeper than prognosed. The wedges previously believed to be of Albian and Aptian were found to be of Aptian and Barremian age, respectively, and sand thickness within the wedges were thinner than anticipated. Oil (3.88 m "net pay" based on wire line data) was found in the Aptian sandstones. However, it was not a commerc