The Combustible Stone of Fergana
The Fergana Valley is an intermountain depression filled with sediments reaching depths of up to 10 kilometers. These layers, deposited since the Jurassic period, contain significant mineral wealth, including coal, oil, natural gas, and oil shale. Uzbekistan holds estimated oil shale reserves of 47 billion tons, a substantial portion of which lies here.
Oil shale is a sedimentary rock containing a solid organic compound called kerogen. It is a misnomer. The rock is often a type of marlstone, and the organic matter is not crude oil. To extract energy, the rock must be heated to approximately 500°C (932°F) in a process called pyrolysis or retorting. This industrial process takes place in the absence of oxygen, thermally decomposing the kerogen into a synthetic crude oil, known as shale oil, and combustible gas. The shale oil can then be refined into various fuel products. The entire operation mimics the natural geological formation of crude oil, but accelerates it from millions of years to mere hours.
Nanoscale Kerogen Droplets
The secret to the Fergana deposits lies at the atomic scale. Analysis using atomic force microscopy (AFM), a technique capable of imaging surfaces at nanometer resolution, reveals a unique characteristic of the kerogen. The organic matter is not a uniform mass but exists as discrete droplets just 5 nanometers in diameter.
This measurement is important. A 5-nanometer sphere represents the near-theoretical minimum size for a droplet of this type of organic matter. Below this size, the carbon atoms are predicted to reconfigure under geological heat and pressure, transforming from a complex hydrocarbon into the crystalline lattice of graphite. The presence of these minimum-sized droplets provides information about the thermal maturity of the deposit and has implications for the efficiency of the retorting process, as the immense surface area of these tiny spheres affects how they react to heat. The Fergana deposits also contain valuable secondary elements within the shale, including vanadium, molybdenum, nickel, and rhenium, which could potentially be extracted as byproducts.