Reservoir quality of intrabasalt volcaniclastic units onshore Faroe Islands, North Atlantic Igneous Province, northeast Atlantic

摘要

The Paleocene and Eocene strata in the western part of the Faroe-Shetland Basin contain abundant volcanic and volcaniclastic rocks. Recently, hydrocarbon discoveries have been made in reservoirs of siliciclastic origin in intra- and post-volcanic strata in the central Faroe-Shetland Basin that show an active petroleum system is present in the volcanic affected area. The siliciclastic reservoirs are present in the same stratigraphic levels as the volcanic and volcaniclastic rocks, and in places, the siliciclastics and the volcanics interfinger. The assumption from published studies so far, based on limited data, is that the volcanic and volcaniclastic rocks are nonreservoir facies. In this study, based on studies of 140 core samples representing more than 70 different volcaniclastic interbeds from onshore Faroe Islands, it is demonstrated that 18 samples are in the helium (He) porosity range of 20% to 43% and a gas permeability range of 1.0 to 110 md, and among these samples, 7 are of epiclastic and 11 of pyroclastic origins. These 18 samples have been investigated further. Among the seven samples of epiclastic origin, five stem from Glyvursnes-1 well Argir Beds that is a fluvial deposit located close to a fault. These samples are correlated and compared with the wireline logs from Glyvursnes-1. Based on this comparison, it is found that the porosity of the Argir Beds is best estimated from wireline logs using V-p (P-wave seismic velocity), V-s (S-wave seismic velocity), or resistivity logs.