Catagenetic Transformation of the Composition and Structure of Insoluble Organic Matter in Deep Jurassic Sediments in the North of the West Siberian Basin
Variation of the elemental and structural-group composition in the course of catagenesis of Jurassic kerogen consisting of the rock organic matter fraction insoluble in organic solvents was studied by the example of deep wells (Tyumen SG-6, Urengoi, En-Yakha, Evoyakha, Yaridei, etc.) in the north of the central part of the West Siberian basin. With an increase in catagenesis downwards along the section from Upper Jurassic to Lower Jurassic sediments, directional carbonization of the kerogen composition is observed: The H/C atomic ratio decreases from 1.2 in mesocatagenesis to 0.5 in apocatagenesis. This is confirmed by the Rouxhet-Robin diagram of the inverse correlation of H/C-at with the vitrinite reflectance, used in the study. With an increase in catagenesis, the relative content of aromatic structures in kerogen increases, whereas the relative content of aliphatic and oxygen-containing groups decreases.
