First Break - Volume 15, Issue 8, 1997

Whether the oil industry likes it or not, environmental considerations are becoming a central concern. According to a new study Environmental Concerns in Offshore Oil & Gas - The Business Implications - by Smith Rea Energy Consultants, 'the current political climate is now one that accepts man-made global warming as a real possibility and reflects real concern about the pollution of the oceans.' A more stringent future Smith Rea's conclusion is that 'there is every indication that environmental regulations will become progressively more demanding and with it the spending of oil companies on the necessary extras.' It does not believe that European governments in general are likely to find a CO2 tax politically acceptable, though a case can be made for its beneficial effect in Norway. If they do accept such a tax, then environmental spending would accelerate even more. With or without it, Smith Rea suggests that the list of related business areas - environmental impact assessments, pollution clean-up, de-commissioning, separation techniques, flare technology, injection, monitoring and controls - is bound to grow.

An element of caution about the future scale and pace of development in the Atlantic Frontier of the UK, Norway and Ireland is sounded by energy analyst Wood Mackenzie in its latest study of the area and the exploitation so far by the oil industry. Wood Mackenzie notes that there has been a considerable interest and commitment to the NW Europe Atlantic Margin by major global upstream players and a number of smaller independents and that advances in drilling and production technology, coupled with competitive fiscal regimes particularly in Ireland and the UK, have ensured that the economics of field developments remain among the most attractive on a global basis. However, the analysis suggests that it will be the early part of the next century before the results of upcoming drilling programmes confirm whether this initial optimism is well founded - particularly given the recent indications of the presence of substantial gas volumes. It concludes that 'only then can the NW Europe Atlantic truly be regarded as a prospective frontier hydrocarbon province which can compete on a global basis.

Combined engineering-scale seismic and magnetotelluric methods are not usually thought of as useful tools for investigating the uppermost (51 km deep) crystalline crust, although combined methods are making progress at the larger oil exploration scale in sedimentary basins (Nagy 1996). By `engineeringscale' we mean those field methods which can be applied by a team of two or three persons with one or two vehicles, with equipment normally used for engineering site surveys, and with survey field costs of only a few hundred dollars per day. We report here a case history where a combination of such modest geophysical resources has been used to try to clarify some regional structural and tectonic relationships which orthodox geological mapping had failed to resolve. The Southern Bohemian Massif in Austria is a deeply eroded remnant of the Variscan orogen of central Europe, comprising medium-grade metamorphic rocks of Precambrian to Palaeozoic age, extensively intruded by granitic plutons of Variscan age. The paper deals with the location of the boundary between two major divisions of the massif, the Moldanubian in the west and the Moravian in the east, in the neighbourhood of the Messern Arc. The geological problem is essentially whether the Moravian Bittesch Gneiss is identical to or distinct from the Moldanubian Dobra Gneiss in the west. Wieseneder et al. (1976) point to the remarkable similarities between the two gneiss units. The two outcrops are separated at the surface by the Variegated Sequence (Fig. 1) and by granulites and paragneisses. Fuchs & Matura (1980) suggest that the surface outcrops are linked at depth by a synclinorial (trough-shaped) structure. If the synclinorial structure is correct, it implies that the boundary between the Moldanubian and the Moravian must lie some 30 km to the west, at the western border of the Dobra Gneiss. If, on the other hand, as Thiele (1976) assumes, the Variegated Sequence and granulites have been thrust eastwards over the Bittesch Gneiss, there is no genetic relation between the two gneiss sequences. This question is the subject of our combined seismic and magnetotelluric investigations. Although our spatially very limited data turn out to be consistent with either models, we demonstrate that modest geophysical techniques can be used to image structures within crystalline basement.