Developing Geothermal Resource Plays Offshore Ireland: A Case Study On The Lower Cretaceous Dunquin North Carbonate Build-Up, Southern Porcupine Basin
The 44/23-1 hydrocarbon exploration well, which was drilled in 2013 by an ExxonMobil-lead group of companies (Providence, 16%), was located in the southern Porcupine Basin, offshore Ireland. The well was situated in c. 1600 metres of water and was c. 170 km off the south-west coast of Ireland. The exploration objective of this well was to evaluate the hydrocarbon resource potential of an interpreted large Lower Cretaceous carbonate build-up prospect (‘Dunquin North’). This well was the first to be drilled in the basin proper, which covers an area of c. 25,000 km2. Once drilling operations were complete, a comprehensive logging and data acquisition programme was carried out given the frontier nature of both the basin and play. The data revealed that the well had encountered a massive (N/G> 90%), porous (>20%) over-pressured (>11,000 psi) Lower Cretaceous carbonate reservoir interval at c. 3,000m BML. Further analysis of mud-log, SWC, MDT and pressure data confirmed that whilst the drilled 250-metre reservoir interval hosted a residual oil column, the mobile fluid phase was water. Temperature logging was also carried out which confirmed a Horner corrected mid-reservoir temperature of 250o F. Seismic analysis confirms that the well was terminated about half-way through the Dunquin North carbonate build-up which is estimated to be c. 500 metres thick. Post-drill volumetric modelling to assess the paleo-oil accumulation indicated that the drilled 250-metre interval could have previously hosted a multi-billion barrel oil accumulation based on available seismic and well data. This volume is likely to increase markedly should the un-drilled lower 250 metres be included in the estimate. Providence recently began to assess the geothermal resource potential of the Dunquin North carbonate build-up which is located c. 275 km from the nearest high voltage grid connection in the Shannon Estuary. Offshore geothermal resource development could prove part of Ireland’s national strategy to reduce CO2 emissions and the associated effects of climate change.
AAPG Datapages/Search and Discovery Article #90346 ©2019 AAPG European Region, 3rd Hydrocarbon Geothermal Cross Over Technology Workshop, Geneva, Switzerland, April 9-10, 2019