UK: Thicker Cladhan oil column penetrated

By OGJ editors
HOUSTON, Apr. 15 -- Sterling Resources Ltd., Calgary, said the first of three planned appraisal wells at Cladhan in Block 210/30a in the UK North Sea found oil in two formations.

The 210/30a-4 well is 1.1 km southeast and 749 ft downdip of the 210/29a-4y appraisal well and was drilled from a centrally positioned location chosen in order to drill three bottom hole targets without moving the rig. The objective of the 210/30a-4 well was to test the eastern extension of the northern channel system and to establish an oil-water contact.

The 210/30a-4 well, drilled to 12,252 ft measured total depth, encountered two reservoirs. The basal reservoir has a gross vertical reservoir interval of 256 ft containing a minimum 21 ft net pay with porosity up to 20%. The net to gross encountered, while lower than the exceptional values found at 210/29a-4z in the centre of a channel sequence, is within the typical range predicted in the geological model for this type of interbedded sand-shale system.

Pressure measurements taken within the basal reservoir zone confirm continuity with the updip wells drilled in the northern channel during 2010. No oil-water contact was observed, and consequently the minimum effective vertical oil column is 1,228 ft.

In addition to the basal reservoir, 210/30a-4 encountered a younger oil-bearing sandstone with 13 ft of net pay in a separate pressure system. Well results and recent seismic inversion tests provide encouragement that these sands will thicken downdip in the fan area to the east, Sterling said.

The next planned well will be a sidetrack 1.8 km southeast of 210/30a-4 targeting what is believed to be a turbidite fan system located even farther downdip. After that Sterling intends to drill a second sidetrack well into an as yet undrilled channel system, the central channel.

Sterling is operator with 39.9% interest in License P1064. Wintershall (UK North Sea) Ltd. has 33.5%, Encore Petroleum Ltd. has 16.6%, and Dyas UK Ltd. 10%.

Meanwhile, Sterling’s Grian 48/28b-2 well encountered good quality Leman sandstone at 6,148 ft measured total depth, failed to find gas, and was plugged and abandoned. Sterling is operator with 57% interest in License P1540. GP Petroleum Ltd. has 43%.