The results of the latest extended well test by Noble Energy on a deepwater discovery off the coast of Equatorial Guinea have indicated that the field could be bigger than first thought, adding further momentum to the operator’s plans for a regional development hub centred on its producing Aseng field FPSO.

Noble’s partner PA Resources of Sweden confirmed that a drill stem test on the Diega I-8 well in Block I had produced better than expected results. An initial pilot hole encountered up to 12 m (39 ft) of vertical thickness “good quality oil pay” and established the deepest known oil on the Diega accumulation, according to PA.

A horizontal sidetrack, Diega I-8ST, then encountered 400 m (1,312 ft) of oil pay of similar quality, with the well then tested using the Atwood Hunter rig for a month at a constrained rate of up to 7,300 b/d. The well, which PA said had confirmed lateral reservoir continuity and the absence of compartmentalisation, has been suspended for reuse as a future producer. The rig has since been released.

The test results will now permit the submission of a field development plan for Diega this year as a subsea tieback to the Aseng FPSO, with a first oil date targeted for 2016.

Mark McCallister, PA’s chief executive, pointed out that Diega was originally given a conservative reserves estimate of 30 MMbbl of oil. “Initial interpretation of these well results is consistent with our expectations of significantly larger reserves, and further Diega drilling is likely in Block I, where the down-dip limit of the field has yet to be established,” he said.

Operator Noble recently indicated that the Greater Diega Area, including the Carla and Carmen deepwater discoveries, could hold between 70-200 MMboe of gross resources, with the oil-gas split being 75-25. It has allocated up to 135 MMboe of gross resources for the initial development phase of Diega alone. Development plans will be finalised by mid-year, with first oil in late 2016 with around 10,000 b/d expected per well.

The Carmen, Carla (in adjacent Block O) and Carla South oil and condensate discoveries (see DI, 22 April 2013, page 1) are likely to also be developed via subsea tiebacks to the Aseng floater or alternatively Noble’s nearby producing Alen production platform as part of the operator’s regional hub scheme for the Douala Basin.

Noble also has plans for an exploration well in neighbouring Cameroon’s waters later this year.

Offshore