Knotty Head Field, Gulf of Mexico, USA

The Knotty Head Field lies in Green Canyon block 512 in the Gulf of Mexico. It is operated by Nexen Petroleum with a 25% working interest. Other equity partners include Anadarko Petroleum 25%, BHP Billiton 25% and ChevronTexaco 25%. The field lies in 3,500ft of water close to the Chevron-operated Tahiti and Tonga discoveries.

The field was discovered in 2005 when the well encountered approximately 600ft of net oil pay in multiple zones in the lower miocene of the Mississippi fan fold belt.

KNOTTY HEAD WELL

The well was drilled by the TransOcean Discoverer Spirit drillship. The well reached a total depth of 34,189ft and is the deepest well drilled in the Gulf of Mexico. The field also set a record for the deepest real-time Logging While Drilling / Measuring While Drilling (LWD / MWD). The well also set a third record for the longest 14¾in-bit run at 11,545ft and a total depth of 24,085ft.

In order to determine the extent of the discovery, Nexen followed this up by a sidetrack well drilled downdip to a total depth of 32,986ft, with a bottom-hole location approximately 4,500ft to the south of the original wellbore. The sidetrack encountered all reservoirs seen in the discovery well and approximately 400ft of net oil pay were logged.

OIL PRODUCTION

Nexen's pre-drill resource estimate for the field, prior to drilling the first exploration well was 350 million to one billion barrels.

Based on the results of this drilling, the resource estimate reduced to 200 to 500 million barrels of oil equivalent.

The initial exploration plan filed by the operator envisages at least four wells to be drilled on GC 512.

Floatec, the 50-50 joint venture between J Ray McDermott and Keppel FELS created to deliver deepwater floating production systems, is finishing a concept screening study for Knotty Head. FloaTEC will evaluate tension leg platforms; spars; floating production, storage and offloading vessels; and subsea options for the field. Both wet and dry tree options will be considered.