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What will happen when methane is at a temperature of 1500 K? On the first glance the answer seems to be obvious ‐ methane will decompose into hydrogen and one of the forms of carbon. Yes. However is does not do so at very high pressure, when novel reaction pathways become possible. The latest experimental results and theoretical calculations show that methane and heavier hydrocarbons are, remarkably enough, stable under extreme pressures and temperatures. Even more, experiments confirm the possibility of abiogenic synthesis of natural gas at 5.0 GPa and 1500 K. The review summarizes published results of theoretical and experimental investigations of possible pathways under the conditions of pressure and temperature that prevail in the Earth's upper mantle for the formation of (1) particular species of hydrocarbon molecules, and of (2) complex hydrocarbon systems. The results raise fundamental questions on the genesis of hydrocarbons.

The deep abiogenic synthesis of hydrocarbons is possible under the conditions of the asthenosphere. We have found that this process can also occur under the mineral and thermobaric conditions of subducting slabs. We have investigated the abiogenic synthesis of hydrocarbon systems at pressures of 2.0–6.6 GPa and temperatures of 250–600 °C. The determined lower thermobaric limit of the reaction at 280–300 °C and 2–3 GPa corresponds to a depth of 70–80 km during cold subduction. The hydrocarbon fluid formed in the slab can migrate upwards through the network of faults and fractures to form petroleum deposits.

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[1] The theory of the abyssal abiogenic origin of petroleum is a significant part of the modern scientific theories dealing with the formation of hydrocarbons. These theories include the identification of natural hydrocarbon systems, the physical processes leading to their terrestrial concentration, and the dynamic processes controlling the migration of that material into geological reservoirs of petroleum. The theory of the abyssal abiogenic origin of petroleum recognizes that natural gas and petroleum are primordial materials of deep origin which have migrated into the Earth's crust. Experimental results and geological investigations presented in this article convincingly confirm the main postulates of the theory and allow us to reexamine the structure, size, and locality distributions of the world's hydrocarbon reserves.Citation: Kutcherov, V. G., and V. A. Krayushkin (2010), Deep-seated abiogenic origin of petroleum: From geological assessment to physical theory, Rev. Geophys., 48, RG1001,

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The transitions to the glassy state in viscous crude oils have been investigated at high pressures by the transient hot-wire method, by differential scanning calorimetry, and by equation-of-state measurements. The range of pressures investigated was up to 1.2 GPa in the temperature interval 150-370 K. The glass transition in crude oils is a common phenomenon and occurs due to the viscosity increase on decreasing the temperature or increasing the pressure. The actual transition coordinates depend not only on physical properties but also on the characteristic experimental time.