3/4-2 S

General

Well 3/4-2 S was drilled on the Ulvetanna prospect in the Søgne Basin in the southern North Sea. The prospect was a salt-induced closure at Late Cretaceous level. The objective of exploration well 3/4-2 S Ulvetanna was to test the hydrocarbon potential of the Paleocene Ekofisk Formation and Cretaceous Tor and Hod Formations, in addition to investigate the maturity level of the potential Mandal Formation source rock.

Operations and results

Wildcat well 3/4-2 S was spudded with the jack-up installation Mærsk Guardian on 18 July 2012 and drilled to TD at 2916 m (2864 m TVD) in the Late Jurassic Farsund Formation. The well was drilled deviated in order to penetrate the steeply dipping potential reservoir levels in a best possible angle and direction. The well was drilled with spud mud down to 1262 m and with Performadril WBM from 1262 m to 2962 m.

The Shetland Group Ekofisk Formation was penetrated at 2638 m (2559 m TVD), the primary reservoir level Tor Formation was observed at 2700 m (2614 m TVD), while the potential secondary target Hod Formation was found at 2769 m (2677 m TVD). Both targets were found to be water bearing. Top Mandal Formation was encountered at 2911 m (2815 m TVD). It was 9 m thick with very high gamma ray. Geochemical analyses of sidewall cores indicated a very good oil-prone source rock (TOC = 5 - 7 %wt; Hydrogen Index = 540 to 600 mg HC/g TOC). Tmax and vitrinite reflectance analyses show that the Mandal Formation has not yet entered the oil window in the well location. The well also penetrated a section of the underlying Farsund Formation (base not seen). Side wall cores indicated oil-prone quality here as well, but not as good as in the Mandal Formation.

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