Analysis of change in the physico-chemical properties of oils depending on the depth and features of deep oils

The article is devoted to the urgent problem of studying the features of the properties of poorly studied oils at great depths (more than 4,500 m), the need for development of which is caused by a reduction in oil production in traditional oil producing provinces. A study was made of changes in the physicochemical properties and occurrence conditions of oils depending on the depth, which made it possible to clarify the quantitative patterns of changes in the physicochemical properties of oils at different depths and to reveal features of the properties of poorly studied deep-seated oils. The studies used information on 21067 oil samples from 167 oil-bearing basins of the world, obtained from the database on the physicochemical properties of oils. It has been shown that in different oil-bearing basins the density and viscosity of oils decreases with depth. The content of sulfur, resins and asphaltenes also decreases with depth, and the content of light fractions and oil gas increases. The paraffin content increases to a depth of 3-4 km, and then decreases with increasing depth. The features of the physicochemical properties of deep-seated oils have been established, which are manifested in a decrease in the density and viscosity of oils, in a decrease in the content of sulfur and asphalt-resinous substances, and in an increase in the content of light fractions and oil gas. The results of geological modeling of changes in the stress state of rocks associated with the displacement of the foundation blocks due to tectonic processes are considered. It has been shown that at the edges of the downing tectonic blocks at the boundary of the sedimentary cover and the basement, zones of minimum pressure (decompression zones) are formed. The lightest hydrocarbons migrate along the faults into the decompression zones, forming deep-seated hydrocarbon deposits, what can serve as a justification for the features of the properties of deep-seated oils established in the work