Peak oil is the point called where petroleum production reaches its maximum level. It’s the point to which all increasing production moves toward, and the point from which declining production descends. It’s based on the Hubbert Curve Theory according to which oil production follows a statistical curve, ascending and descending as the more easily recovered oil is extracted and the oil that is more difficult to extract is withdrawn later.
Four of the five major petroleum companies have published reports that they have reached peak oil production and that discoveries for new sources are continuously declining. Economic analysts project that with China, India and Brazil becoming major energy consumers, the demand for petroleum will easily triple by 2100, more likely be four to five times higher. Such a situation would likely lead to petroleum production interruptions and extremely high consumer prices. In addition, political blackmail by unstable governments raises the specter of violent conflict.
One favored alternative are kerogen-based fuels. Kerogen is a solid, waxy, organic substance that forms when pressure and heat from the Earth act on the remains of plants and animals. It resides in sedimentary rocks as an insoluble in common organic and inorganic solvents. It is thought to be a pre-petroleum hydrocarbon substance which, due to unfavorable conditions, did not complete the petroleum formation process. Kerogen converts to various liquid and gaseous hydrocarbons at a depth of seven or more kilometers and a temperature between 50º and 100ºC. Like petroleum, refineries can distill kerogen into different usable hydrocarbon products. Kerogen is found in two geological formations – the first is oil shale and the second tar sand.
Oil shale refers to a sedimentary rock that contains kerogen. When the rock is heated in the chemical process of pyrolysis, it releases petroleum-like hydrocarbons. Oil shale, like petroleum, is formed over hundreds of millions of years as organic debris under silt deposits on lake beds and sea bottoms. In a process similar to the one that forms oil, heat and pressure transform the materials into oil shale. However, the heat and pressure weren’t as great.
Tar sands (also referred to as oil sands) are a combination of clay, sand, water and bitumen, a heavy black viscous oil. Tar sands can be mined and processed to extract the oil-rich bitumen, which is then refined into oil. The bitumen in tar sands cannot be pumped from the ground in its natural state; instead, tar sand deposits are mined, usually using strip mining or open pit techniques, or the oil is extracted by underground heating with additional upgrading.
Extracting kerogen from oil shale and tar sands is more complex than conventional oil recovery and also more expensive. Since kerogen is a solid substance, it cannot be pumped directly out of the ground. Usually, it is mined and then heated to a high temperature to separate it from the surrounding substrate. One alternative experimental process, referred to as in situ retorting, injects heating the kerogen while it’s still underground. It can then be pumped as a liquid to the surface. In either process, the resultant liquid is heated further, separated and the hydrocarbons collected.
At the present time, extraction of kerogen is more costly than drilling for crude oil. But with the politicizing of petroleum production, the market failures surrounding fossil fuel usage and peak oil concerns of major petroleum suppliers, it’s likely that federal subsidies for fossil fuel recovery will begin to support alternative fuel sources, making the cost less of an issue.