Project Profile
Location: North Sea
Area: 400km²
Relinquishment Date: 16/10/2015
Fairfield Energy has started of a 400km² Broadband 3D seismic survey over the recently awarded 27th Round Licence P2089 Block 43/28. The survey will be acquired by Polarcus and will fulfil the firm commitment work programme on the licence, where wholly owned subsidiary Fairfield Cedrus Limited is operator with a 50% interest along with partner Viking UK Gas Limited, a wholly owned subsidiary of Third-Energy (also with a 50% interest).
Until the acquisition of the 2013 Polarcus Greater Ravenspurn survey following the award of this block to Fairfield in the 27th Round, only 2D seismic existed across the block. This was unable to resolve the detail of the sub-salt Carboniferous interval and therefore it was difficult to determine the presence or termination of individual Carboniferous units across the Otter anticlinal structure. The 43/28 block was evaluated using a combination of PGS Megamerge data and the Polarcus 2013 Greater Ravenspurn 3D seismic survey. The 1625 km2 Greater Ravenspurn survey was acquired in 2013 and fully covers the 242 km2 of block 43/28. PSTM processing was completed in Q2 2014.
Following the seismic interpretation of the acquired 2013 3D Greater Ravenspurn seismic survey in conjunction with geological analysis of the 43/28-1 discovery well and offset wells the following interpretations have been made:
The large anticlinal structure of Otter interpreted from the 2D seismic remains robust on the 3D seismic interpretation even considering depth conversion uncertainties below the salt, although it is more limited in extent the revised closure being constrained to only the southern half of the original structure.
The improvement in seismic character below the Permian salts has led to the identification of truncation surfaces of the intra-Carboniferous horizons below the Base Permian Unconformity although some uncertainty remains as geologically the Namurian interval is poorly reflective.
The identification of the intra-Carboniferous horizon truncations has led to the conclusion that the better quality Westphalian reservoir intervals are eroded across the Otter anticlinal structure. In addition the truncation of the Namurian Trent sandstone reservoirs is located on the structure and therefore these reservoirs are of limited aerial extent over the structure.
Offset well data indicates the presence of good quality incised valley sandstone deposition in parts of the Namurian but it is not possible to identify the location of these depositional environments from the seismic.
Identification of the gas down to in the 43/28-1 discovery well indicates that the Carboniferous structure is not filled to spill which is unusual given the complete filling of all offset fields. There is however evidence of some gas within the Rotliegend sediments across the Otter structure and the gas down to identified within the 43/28- 1 well shows similarities to the closure at Top Rotliegend and so it is interpreted that the closure incorporates the Rotliegend and Carboniferous sections with the Rotliegend being shale rich in this area.
In conclusion, due to the reduction in extent of the Otter anticline and the limited aerial extent of the reservoir sandstones across the structure the expected gas-in-place is significantly reduced compared to that identified during the application for the licence ranging from 13.5 Bcf to 50.4 Bcf. Given the tight nature of the reservoir which would require fraccing to produce at economic rates the volumes are too low to deliver a commercial project.
Operators:
Fairfield Cedrus Limited: Operator with 50% interest
Viking UK Gas Limited: 50% interest
Contractors:
Polarcus: Seismic Survey