oljeskiffern

Oil shale, or oljeskiffern, is a sedimentary rock rich in kerogen, an immature organic matter that yields liquid hydrocarbons when heated. In contrast to conventional crude oil, the organic material is solid and requires processing through pyrolysis or in-situ heating to produce shale oil, which can be refined into fuels and chemicals.

Formation and composition: Oil shale forms from fine muds and carbonate-rich sediments that accumulate in lakes or lagoons. The kerogen type (I–III) and mineral matrix determine the potential oil yield. Oil yields vary widely, typically tens to hundreds of liters per tonne, depending on grade and processing efficiency.

Global distribution: Notable deposits exist in Estonia, the United States, Russia, China, Jordan, and smaller occurrences across Europe and the Middle East. Estonia historically developed oil shale mining and used shale-fired power generation, while other regions extract and process shale oil for fuels or feedstock.

Extraction and processing: Commercial recovery often begins with open-pit mining, followed by crushing and heating in retorts to drive off liquids from kerogen. In-situ approaches aim to heat the deposit underground. The produced shale oil is upgraded in refineries. The process is energy-intensive and water-demanding and generates significant carbon emissions and solid wastes.

Economics and environmental aspects: Oil shale has faced economic and environmental scrutiny, as higher production costs, emissions, land use, and water impacts challenge its competitiveness with conventional crude and tight oil. Some regions continue to utilize oil shale for electricity, liquid fuels, or chemical feedstocks where deposits and infrastructure permit.