Journal of Petroleum Geology, Vol.15,
No.1, pp. 51-70, 1992
©Copyright 2000 Scientific Press,
Ltd.
HYDROCARBON POTENTIAL OF
NORTHERN IRELAND:
Part III. Reservoir potential of the Permo-Triassic
J. Parnell*
* School of Geosciences, The
Queen's University of Belfast, Belfast BT7 1NN.
Abstract
Thick Permo-Triassic sandstones occur in
two basins in Northern Ireland. The sandstones are
fluvio-deltaic, including an oolitic facies, and are interbedded
with mudrocks. They exhibit petrographic features which are
typical of red beds and are widely found in the Permo-Triassic
elsewhere in the British Isles. The predominant cements are
haematite, potassium feldspar, illite and carbonates. Gypsum,
anhydrite and dolomite cements occur in the regions of deepest
burial, which represent the basin centres. There was widespread
leaching of carbonate/sulphate cements, but calcite is preserved
in the oolitic facies and below the sub-Cretaceous (chalk)
unconformity. The dissolution of cements and framework grains was
due to leaching by meteoric fluids. Precipitation of kaolinite in
secondary pores, and subsequent illitization, represent
fluctuations in the meteoric hydraulic head. Deep boreholes
exhibit sandstone porosities which indicate that there may be
significant reservoir potential where adequate seals and traps
are present.