Signs of oil in first deepwater well offshore western Ireland

ExxonMobil plans to P&A its first deepwater exploration well offshore southwest Ireland.

Offshore staff

DUBLIN, Ireland – ExxonMobil plans to P&A its first deepwater exploration well offshore southwest Ireland.

The44/23-1 Dunquin North exploration well in frontier exploration license (FEL) 3/04 was drilled in around 1,700 m (5,577 ft) of water, 170 km (105 mi) from the southwest coast.

Drilling started in late April on the structure, situated on the northern flank of a 700-sq km (270-sq mi) intra-basinal ridge system in the southern Porcupine basin. Operations concluded on July 15 after reaching TD of 16,400 ft (4,999 m) MDBRT.

According to partner Providence Resources, the primary Lower Cretaceous Dunquin target comprised a thick overpressured carbonate reservoir system. The well was terminated after drilling through 800 ft (244 m) of porous carbonate reservoir.

Early well analysis indicates the reservoir is water bearing. However, petrophysical log interpretation, elevated gas levels, and oil shows in sidewall cores over the upper 144-ft (44-m) section of the reservoir suggest there could be a residual (i.e. non-producible) oil column.

John O’Sullivan, technical director of Providence, said: “TheDunquin exploration play comprised two interpreted carbonate features, Dunquin North and Dunquin South. The presence of a potential residual oil column may indicate that hydrocarbon entrapment has occurred at Dunquin North but that the oil has subsequently leaked.

“Top seal integrity had been identified pre-drill as a possible risk for Dunquin North, with fluid escape features and seabed core hydrocarbon anomalies present over the prospect. Notably, the separate Dunquin South build-up appears to have a thicker seal and lacks the significant fluid escape features seen further to the north.”

Tony O’Reilly, Providence CEO, added that the well “demonstrated that all of the key components of a working petroleum system exist in the southern Porcupine basin. These data are encouraging not just for the adjacent Dunquin South prospect, but also for the basin in general and are likely to intensify the already growing industry focus on this emerging hydrocarbon exploration arena.”

Pre-drill studies had indicated that the basin would be gas-prone. Providence says the focus will likely shift now to the separate Dunquin South build-up. Seismic mapping suggests this feature has a much thicker seal and lacks the fluid escape features evidenced to the north, so any potential oil accumulation may still be in place.


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