License P2390 covers blocks 23/26e and 30/1d and contains the Isolde low risk – shallow prospect. Soliton considers that over time this prospect has been overlooked, mainly because of seismic imagining limitation on 3D data, and that can potentially be a sizeable exploration target if modern processing/visualisation techniques are applied.
The Isolde prospect is a typical Central North Sea (CNS) salt diapir flank trap. This prolific trap type has a 100% success record in the main part of the CNS, where more than a dozen of such fields being found. These have an average hydrocarbon column height over 900 m and average recoverable reserves around 100 MMboe.The flank of the Isolde salt diapir was drilled in 1992 by well 23/26-17 and encountered oil and gas shows in the regional Paleocene Forties Sandstone Member reservoir.
The Forties Sandstone Member consists of fine to coarse sandstone interbedded with medium to dark grey siltstone and mudstone. The sandstone is moderately to poorly sorted, and locally pebbly; beds of muddy, extremely poorly sorted, pebbly sandstone are also encountered.
The 23/26-17 well penetration is interpreted to lie a short distance below the base of a retreated hydrocarbon column. This interpretation is based on a close analogy with several similar CNS diapir flank fields which have residual oil zones of 30 m to 120 m thickness immediately below the oil-water-contact.
The Isolde structure was only partially imaged on poor quality legacy 3D seismic data, on which around 600 m of top reservoir relief above regional level could be mapped.
The Isolde prospect is surrounded by large oil and gas fields that target the Chalk Group and Palaeocene sandstone reservoirs. Potentially recoverable resources are in line with the average of the analogous fields, split approximately 80:20 between the chalk and sandstone reservoirs. Chance of exploration success is appreciably better than 1 in 2, reflecting both the 100% success ratio of this trap type in the study area and the proximity of similar, large fields.
Soliton will be reimbursed for the license costs accumulated so far. Equinor will also pay for the option to drill and cover all future costs related to Soliton’s retained 15% shares in the license.
Soliton managing director Graham Goffey is confident in the prospectivity of Isolde, affirming that farm-out process was competitive and that Equinor was the right choice in further exploring the prospect. He adds “Soliton’s application for the Isolde prospect in the UK’s 30th licensing round was facilitated by the Oil and Gas Authority’s flexible ‘Innovate’ licence structure and its data access initiatives, which have lowered the barriers to entry for newly established companies such as Soliton.”