7/11-12 S

General

Well 7/11-12 S was drilled on the Peking Duck Prospect located 19km SW of the Ula Field and 28km NE of the UK Jade Field. The primary objective was to evaluate Triassic sandstones at a prognosed depth of 5212 m.

Operations and results

Wildcat well 7/11-12 S was spudded with the jack-up installation Mærsk Gallant on 27 March 2011 and drilled to TD at 5420 m (5403 m TVD) in the Triassic Skagerrak Formation. Due to the possible risk of shallow gas, a 12-1/4" pilot hole was drilled from 255 m to 950m. No shallow gas was observed. There were no major problems involved in the operations, but due to deteriorating hole conditions wire line logging at TD was terminated without obtaining satisfactory XPT pressure data. The well was drilled with seawater and hi-vis sweeps down to 255 m, with KCl/Polymer mud from 255 m to 964 m, with Versatec oil based mud from 964 m to 3900 m, with Paratherm Oil based mud from 3900 m to 4964 m, and with WARP oil based mud from 4964 m to TD.

As prognosed, the Forties Formation was present as a water wet, poorly developed sandstone with argillaceous interbeds. The Jurassic J62 sand (Ula Formation) was penetrated at 5197 m (5181 m TVD) and the Triassic Skagerrak Formation at 5212.5 m (5197 m TVD). A 40 m hydrocarbon column was identified from the top of the J62 sandstone down to a Gas Down To (GDT) at 5237 m (5221 m TVD) in the Triassic Skagerrak Formation. However, with a 9.1 % porosity cut off there were no net pay in the J62 sandstone. In the Triassic 16.5 m net pay with 10% average porosity was estimated. The only oil shows above the oil based muds used in the well was recorded on shales in the Mandal Formation.

No conventional cores were cut an