A new hub-and-spoke development centred on a significantly upgraded oil discovery in the deepwater Gulf of Mexico is likely to see a Truss Spar platform employed as the production facility.

DI hears that, following Anadarko Petroleum’s confirmation of a major upgrade in expectations for its Shenandoah discovery in the Walker Ridge area following its latest appraisal well, the operator is keen to push on with its’ tried and tested formula of employing spar production platforms on its hub fields in the GoM. Having already followed the ‘design one, build two’ philosophy for its 400 MMbbl Heidelberg field (mirroring its 80,000 b/d capacity Lucius facility currently under construction, and due for transport to the field location in Keathley Canyon in Q2 2013), DI understands the operator is studying essentially applying that favoured ‘look-a-like’ formula once more.

Anadarko’s CEO Al Walker has gone on record previously as to the reasons why – it estimates the construction approach results in “significant cost savings”, and enables it to shorten the expected development cycle to first oil for a project of this scale “by up to 18 months”.

If it does eventually follow this development path for Shenandoah, the spar will – like the others – almost certainly be built at Technip’s yard in Pori, Finland. Lucius is the seventh spar Technip has built for Anadarko.

The company’s sudden focus on Shenandoah and the wider Shenandoah basin as a likely new production hub in the Lower Tertiary play comes following an appraisal well that could double or triple previous estimates for the find in Walker Ridge Block 51. The Shenandoah-2 well hit more than 305 m (1,000 net ft) of oil pay in multiple high-quality Lower Tertiary-aged reservoirs, making it one of the company’s largest oil discoveries in the GoM.

The reservoir rock and fluid properties were also of “much higher quality than previously encountered by industry in Lower Tertiary discoveries,” said Bob Daniels, the company’s Senior Vice President, Deepwater and International Exploration. “With ownership in the successful Shenandoah wells, the adjacent Yucatan prospect, and the very encouraging results from the nearby Coronado well (see separate story, page 4), Anadarko is strategically positioned in the Shenandoah Basin, which has the potential to become one of the most prolific new areas in the deepwater GoM.”

Shenandoah-2 was drilled to a total depth of 9,572 m (31,405 ft) in 1,768 m (5,800 ft) of water, more than one mile southwest and approximately 518 m (1,700 ft) structurally down-dip from Shenandoah-1 in WR52, which hit more than 91 m (300 ft) of oil pay in 2009. The appraisal was drilled to test the down-dip extent of the accumulation, and the targeted sands were full to base with no oil-water contact. The results are similar to ExxonMobil’s results from a recent well on its Lower Tertiary Hadrian North discovery.

Further appraisal drilling to advance this “potentially giant project” will be carried out, added Daniels.

Anadarko operates the block with a 30% stake, with its partners being ConocoPhillips (30%), Cobalt International Energy (20%), Venari Resources (10%) and Marathon Oil (10%). Anadarko also has a 15% interest in both the Coronado well in WR 98, and the Yucatan prospect in WR95.

Previous estimates by Anadarko for Shenandoah were around the 300 MMbbl recoverable reserves mark but that figure could now expand to between 500-600 MMbbl.

- Shenandoah partner Cobalt has also confirmed hard on the heels of the Shenandoah announcement that its nearby North Platte-1 well in Garden Banks Block 959 encountered more than 168 m (550 net ft) of oil pay in multiple high quality Inboard Lower Tertiary reservoirs. The field is located in 1,341 m (4,400 ft) of water and was drilled by the Ensco 8503 rig to a total depth of approximately 10,516 m (34,500 ft). Appraisal plans will be decided later this year, which could eventually see the field tied back to a central Shenandoah basin hub facility.

Offshore