Effect of Sub- and Supercritical Water on the Transformation of High-Molecular-Mass Components of High-Carbon Rocks from Unconventional Formations (A Review)

State-of-the-art in the field of recovering high-molecular-mass hydrocarbon components of bituminous and shale rocks by intrastratum transformation into readily recoverable forms using sub- and supercritical water is analyzed. The phase composition of water and its properties in the critical state and the transformations of a number of substances in subcritical (SBW) and supercritical (SCW) water are discussed. The substances under consideration include model polycyclic and heteroatomic compounds containing nitrogen, sulfur, and oxygen, metal porphyrin complexes, asphaltenes, oil sands, and heavy oils and organic matter (OM) of kerogen-containing shale rocks. The preventing effect of hydrogen donors and catalysts for hydrogenation and oxidative cracking on the coking in the course of transformation of heavy hydrocarbons in SCW is compared. The catalytic effect of the mineral matrix of rocks in the course of generation of oil fractions from them is analyzed in detail. The published data concerning the possibility of using SBW and SCW for the transformation of high-molecular-mass components of high-carbon dense rocks from unconventional formations demonstrate high potential of hydrothermal and supercritical fluid technologies.