Abstract: Exploration in the East Irish Sea. A Basin Analysis Approach

HAIG, D. BRIAN, TERRY PIMBLE, MARTIN NORVICK, FRANK PEEL, and STEVE PICKERING

To date approximately 80 exploration and appraisal wells have been drilled and approximately 8TCF of gas and 150mmbo of oil have been discovered within the East Irish Sea Basin. The discovered hydrocarbons comprise predominantly low sulphur sweet gas in the north of the basin and high sulphur gas and oil in the southern Dart of the basin. This mix of hydrocarbon types within the basin reflects a complex source maturation, migration and hydrocarbon preservation history.

All the commercial hydrocarbons discovered to date are reservoired within lower Triassic eolian and fluvial sands which formed in response to east-west extension. These are sealed by an overlying thick sequence of upper Triassic muds and evaporites of Mercia Mudstone Group. Shales and muds of the lowermost Namurian form the source for the sour oil and gas deposits found in the south of the basin, whereas the sweet gas deposits are sourced from Westphalian coal deposits.

An understanding of the distribution, the maturation history and the present day preservation of the source facies is crucial in interpreting and predicting the distribution of hydrocarbons within the basin.

The East Irish Sea Basin has undergone a complex structural history involving several phases of extension, uplift and erosion resulting in two or more phases of hydrocarbon generation and migration. Understanding of this structural history is complicated by the complete absence of any post-Triassic sedimentary record both within and around the basin.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria