Deep History: Scandinavia's Alum Shale
Exploration in Scandinavian Alum Shale goes way back
If you’re looking for exploration activities in Europe with a bit of history, you might want to check into the history of the Scandinavian Alum Shale, which goes back a decade or two.
Niels Schovsbo, Senior Reservoir Geologist & Geochemist at the Geological Survey of Denmark & Greenland provided an update on the Scandinavian Alum Shale to delegates at Shale Gas Results in Europe 2011 in Warsaw, Poland.
He explained that the exploration of Scandinavian Alum Shale extended far back into the 1600s as alum salt was then extracted there. “Apart from that extraction it was also used for oil shale in 1930-50, used as a uranium source later and multi element exploration took place even later in central Sweden and Denmark.
He gave mention to conventional oil and gas exploration, in Sweden, Poland and the Baltic countries.
Schovsbo’s presentation noted the Shell exploration license (2007-11) in Scania and nine licenses in South Central Sweden for Gripen Gas (2010) and Energigas (2011); in Denmark he listed Schuepbach’s licenses on Zeeland (2009) and licenses on Zeeland and in Jutland for Devon Energy Netherlands BV (2010).
“This is a very early stage and I don’t have these exciting data that others have presented,” said Schovsbo. “We have basic black shales: Cambrian, Ordovician, upper Ordovician, lower Silurian – up to 15% TOC in mature areas.”
He also spoke of some other deep history – things that happened 458 million years ago regarding the Alum Shale’s plate configuration.
“Mid Cambrian to lower Ordovician is where the Alum Shale is deposited, he said, adding that it was up to 160 meters thick offshore and onshore 30-100 meters.
The Alum Shale characteristics, he said, were that it was a black laminated mudstone, contained abundant pyrite and had enrichment in redox sensitive metals like uranium, nickel, etc. In terms of it mineral composition, he said it contained high quartz content (50-65%), feldspar of 5-15% and mica 10-15%.
In terms of shale gas activity for the Alum Shale, Schovsbo recalled that it had taken place from 2008-11 in Sweden, in southern Scania, where concessions were awarded to Shell. He commented: “They drilled three wells, but found it uneconomic.”
He said that 2D seismic data was also required.
In the Zeeland area of Denmark, Schuepbach Energy was awarded an exploration area, until 2015, but no seismic or drilling has been made. There and in Jutland areas were awarded last summer to Devon Energy Netherlands BV, but farmed out to Total SA. No seismic or drilling had taken place there yet either.
Since last fall, new licenses have been awarded in South Central Sweden, to Gripen Gas last September, and to Energigas in January.
“Now it’s taking off in the central part of Sweden. We have silts in the area. I can imagine this play can only be drilled if there is a biogenetic gas component,” he said.
Schovsbo reported that the Alum Shale was involved in the GASH (“Gas Shales for Europe”) research project. “It’s one of the target formations for this project, selected as one out of three.”
There’s a new scientific well from which new data was emerging, according to him. “We have very neatly demonstrated the TOC content. We are currently investigating the physical properties and the geomechanics,” said Schovsbo.
Among his conclusions he said Alum shale is preserved in a structurally complicated area in Denmark.
“It’s undoubtedly a high risk play,” said Schovsbo, who said he suspected that was why explorations efforts thus far had not proven conclusive.