Pyrogenic Reservoir Rocks as a Factor of Geofluidodynamic Inhomogeneity

Resumo

This article considers the Kansk–Achinsk brown coal basin. Huge reserves of solid organic matter (OM) are concentrated in the Jurassic sandy–clayey sediments; e.g., the average thickness of the Itatskii layer (Borodino deposit) is 51 m. Attention is drawn to the paleo-centers of heat generation where the coal layers lost (entirely or partly) their OM, which was destroyed by underground fires of eras past. The loss of large OM masses was accompanied by local deformations of the coal layers (and overlapping ones), emergence of burned and caved ground, cave-in topographic forms (subsidence, craters, bolsons), and, most importantly, the formation of epigenetic cavernosity and pyrogenic reservoir rocks. The increased fluid conductivity of burned rocks persists up to the present. The areas containing burnt rocks can be regarded as independent fluid dynamic structures characterized by specific parameters (filtration coefficient, water transmissibility, etc.). It has been suggested that pyrogenic reservoir rocks could have formed in oil and gas basins with coal shale sediments at certain stages of geological development, and at the productive depths they are may be potential reservoirs of catagenic hydrocarbons.