Siljan Ring proved inconclusive. Drilling for natural gas was resumed in the late 2000s and continues as of mid-2012. The scientific premise for prospecting of this sort is based on the work of physicist Vladimir Kutcherov, who is cooperating with Igrene, the company financing the drilling operations. Siljan Ring The Siljan Ring () is a prehistoric impact crater in Dalarna, central Sweden. It is one of the 15 largest known impact craters on Earth and the largest in Europe, with a diameter of about . The impact that created the Siljan Ring occurred when a meteorite collided with the Earth's surface during
Siljan Ring by rocks of the Llandovery series (Lower Silurian). During the last ice age the area was covered by a thick icesheet. The bedrock was sculpted by the ice, with the softer Palaeozoic sedimentary rocks being preferentially eroded. These erosional hollows are now occupied by lakes Siljan, Orsa, Skattungen and Ore. In accordance with theories about abiogenic petroleum (that hydrocarbons can be formed without involving material from dead plants and animals), astrophysicist Thomas Gold suggested that there might be major deposits of oil and natural gas in the area. Drilling was carried out in the late 1980s and early 1990s but