Paper No. 4
Presentation Time: 9:45 AM


DAHLQVIST, Peter, Geological Survey of Sweden, Lund, 227 38, Sweden and ERLSTRÖM, Mikael, Geological Survey of Sweden, Kiliansgatan 10, Lund, SE-22350, Sweden,

The interest in exploration of shale gas has exploded worldwide, partly due to technological advances such as horizontal drilling and fracking making it possible to get vast amounts of gas from shales. At the same time the fracking method is associated with major environmental threats and the population in Sweden is very concerned. Additionally, official reports in Europe and US have overestimated the size of gas available in Sweden. Therefore, we present the distribution, the stratigraphy and the geochemical characterization of the dark shale formations in Sweden.

The bedrock of Sweden is dominated by crystalline rocks belonging to the Fennoscandian Shield. Only in a few regions, coherent areas with sedimentary strata can be found. These areas are associated to the Caledonian Thrust Belt, the Bothnian Sea, the Baltic Sea Basin, the Sorgenfrei-Tornquist Zone and the Swedish part of the Danish Basin, i.e. SW Scania. Isolated scattered erosional remnants of a former extensive cover of Palaeozoic strata are also found on the Shield, i.e. in Västergötland, Östergötland, Närke and Siljan area. The sedimentary deposits include Cambro-Silurian and Mesozoic successions with a number of dark and bituminous shale formations. The late Silurian Rastrites Shale and the upper Cambrian- lower Ordovician Alum Shale, are the most interesting gas prone shale formations in Sweden. The areal distribution of these shales is limited, and additionally the majority of these shales are in a position of only a few hundred meters depth. Thus, the total amount of gas is very limited in a national perspective, and the mere part is present at such shallow depths that the fracking method is not an applicable method. Only in a few areas in Sweden are there theoretical probabilities for deep gas exploration. Recent discoveries from three deep (>1000m) drillings in Scania (the late Silurian Rastrites shale) however point to a very limited amount of gas available even in these areas.