35/3-2

General

Whereas Saga Petroleum operated license 041, BP operated wildcat well 35/3-2 under license 041 by special agreement. The well was the second well drilled on this block, 35/3-1 was abandoned in the Middle Jurassic due to high calculated pore pressures. Well 35/3-2 was drilled on a westerly dipping fault block. The primary target of the well was Early Jurassic sandstone, secondary targets were any other Jurassic sandstones encountered.

Operations and results

Wildcat well 35/3-2 was spudded with the semi-submersible installation Sedco 707 on 19 May 1980 and drilled to TD at 4400 m in ?Caledonian age basement rocks. The well was drilled with seawater and gel down to 902 m, with gypsum/CMC mud from 902 m to 2305 m, with Poly RX/Drispac from 2305 m to 3833m, and with Poly RX/Lignosulfonate mud from 3833 m to TD. The well started to flow while drilling the 24" hole. Heavy mud was pumped down the hole, but there was very little difference between the fracture gradient and the bottom hole pressure and returns were lost several times. A loss/gain situation was maintained until the casing setting depth was reached. When running the 18 5/8" casing the string parted and 22 joints were left in the hole. The string was recovered successfully, and a new string was run and cemented without problems.

The well penetrated strata from Tertiary through Jurassic and Triassic before reaching basement. Hydrocarbon shows were encountered in Lower Cretaceous and Lower Jurassic sands. The primary target Jurassic sandstones were found to be very tight, and no DST was carried out in these. In stead two zones in the Lower Cretaceous Sandstone were tested, producing water and gas/condensate respectively. The lower Cretaceous sands are interpreted as submarine fan deposits. The Lower Jurassic coarsening upward sequences may represent offshore open marine bars cut by tidal channel deposits and capped by a transgressive marine sheet sand. Log