Analysis of the regularities of change in the physico-chemical properties of oils depending on the depth

Analysis of information from the database on the physicochemical properties of petroleum shows that the largest reserves of petroleum resources are concentrated at depths of up to 2 km. The analysis of the distribution of oils by physicochemical properties at depths of up to 6 km showed that in different oil basins the density and viscosity of oils decrease with depth. The content of sulfur, tar and asphaltenes decreases with depth, and the content of paraffins increases to a depth of 3–4 km, and then decreases with increasing depth. The geological modeling of changes in the stress state of rocks as a result of the displacement of the foundation block as a result of tectonic processes was carried out. It is shown that on the border of the sedimentary cover and the basement, at the edges of the descending blocks, zones of minimum pressure values, called decompression zones, are formed. The lightest and most mobile hydrocarbons migrate to fracture zones in the basement rocks, forming deposits in the basement. This may be the explanation of the above regularities in the change of the physicochemical properties of oils with an increase in the depth of occurrence.