Rock properties of hyaloclastic rocks. Evaluation of results and recommendation for further work

The present report gives an evaluation of the analytical results from the project "Rock Properties of Hyaloclastic Rocks" that has been carried out in collaboration between GEUS and the Atlantic Margin Group (Statoil, Enterprise Oil and Mobil). In addition to the analytical work, the project also included field studies on Nuussuaq in the summer of 1998 with participatation from GEUS, Geological Museum and the Atlantic Margin Group with consultants and collaboration partners. The results from the field studies which focussed very much on the different volcanic facies and their geometries will be reported elsewhere by the Atlantic Margin Group and its consultants.

The initiation of the analytical part of the project took place foliowing informal discussions between GEUS and the Atlantic Margin Group on problems of volcanic rocks in petroleum exploration. In particular the possibility of volcanic rocks acting as seal or reservoir, and as migration conduit to possible overlying reservoirs was discussed. These problems may be critical in the evaluation of new exploration possibilities around the Faroe Islands, in other North Atlantic areas, and in many areas on- and offshore West Greenland.

Generally there are relatively few data available in the literature on petrophysical properties of different volcanic rock types; this is the case for both standard reservoir properties, petrophysical log data and their correlation to measured core data, and acoustic data that can be used in geophysical modelling. GEUS therefore proposed to use the unique core material from Nuussuaq to get some basic data that could be useful for the Atlanctic Margin Group in future exploration. The volcanic succession in the Disko-Nuussuaq area has been intensively studied through several decades (see e.g. papers by Pedersen, 1985; Pedersen et al., 1993, 1996, Larsen et al., in press and references therein) and during recent exploration nearly 2 km (!) of drill cores through the volcanics have been obtained. This gives a good chance to study the variation of petrophysical properties of different volcanic rock types and the differences between volcanic rocks with and without oil-impregnation, as these features are very common both in cores and at the surface on Nuussuaq.