Energy

Oil shale

Clays that are rich in organic substance are the most common mother rocks and many clays (oil shale) can contain large amounts of organic substance that has still not been completely transformed into hydrocarbons (kerogen), dispersed in small particles or concentrated in thin lenses or laminas: kerogen is typical in mother rocks that were never buried deep enough to generate hydrocarbons. If the kerogen content is greater than 8% of the weight, the rocks may be considered potential future reserves: this content guarantees a production of 40 l of oil per tonne of rock. In the richest oil shale, approximately 12-14% of the weight consists of oil: in the Green River Formation (Colorado, USA), exceptional values of 16% are reached. Kerogen is very abundant but it is difficult to extract; in fact it is scarcely mobile and it is not easy to separate it from the rock, and furthermore clays have a very low permeability therefore it is improbable that these hydrocarbons can account for more than 10% of the world resources. Tar shale and clay contain reserves amounting to 2,600 Gbbl, of which 2,000 are in the territory of the USA (Green River in Colorado, Uinta Basin in Utah and Washakie Basin in Wyoming), the rest is distributed between Brazil , Australia, China and Estonia. In an international scenario, use of non conventional hydrocarbons should not only lead to an increase in the reserves but also to a greater diversification of the extraction sites ( that are no longer prevalently concentrated in the Middle East) thus making the price of oil more stable, as it is less sensitive to the geopolitical scenarios and international crises. Serious environmental problems caused by “non conventional” extraction still have to be solved.