7121/7-1

General

Well 7121/7-1 was drilled in order to test the Lower/Middle Jurassic sandstone on the eastern part of the Albatross structure on Tromsøflaket. The primary target was defined as sandstone intervals in Early-Middle Jurassic and Late Triassic.

Operations and results

Wildcat well 7121/7-1 was spudded with the semi-submersible installation West Vanguard on 11 June 1984 and drilled to TD at 2160 m in the Late Triassic Fruholmen Formation. No significant problems were encountered during drilling. The well was drilled with spud mud down to 764 m and with a gypsum/polymer mud from 764 m to TD.

Logs, RFT pressure gradients, and cores indicated gas in the Lower/Middle Jurassic sandstone (Stø Formation) encountered at a depth of 1849 m. Gas/water contact was evaluated to 1902.5 m RKB, the same as found in well 7120/9-1, also drilled on the Albatross structure. From the GWC down to TD in the well shows were observed in sandstones on cores and cuttings. Four cores were cut in the interval 1851 m to 1935 m in the Stø Formation. Two segregated samples were taken, at 1900.2 m and at 1851.0 m. The 2-3/4 gallon chamber from 1900.2 m was bled off offshore and gave an opening pressure at 2220 psig. The sample contained 58.25 cuft of gas and 1 litre of liquid consisting of 800 cc water/mud filtrate and 200 cc condensate. The 2 3/4 gallon chamber from 1850.5 m contained 2200 psig with 4500 cc water based liquid, a small volume condensate, and 41 cuft of gas.

The well was permanently abandoned on 5 August 1984 as a gas appraisal well.

Testing

Two DST were performed, one water test over the interval 1947.2 m to 1960.18 m and one gas test over the interval 1867 m to 1872 m. The recorded temperatures were in agreement with those observed in well 7120/9-1. The reservoir fluids had the same composition in well 7121/7-1 as in well 7120/9-1. The sandstone in the tested water zone had good reservoir properties. The