Abstract:
© SGEM2018. On the example of 50 heavy oil fields prepared by PJSC «Tatneft» for pilot development in the territory of Tatarstan, the relationships of the changes in their properties: density, sulfur and paraffin content with the oil-bearing area, effective average oil-saturated thickness of reservoir productive rocks, as well as with coefficient of their sand content, permeability and porosity were investigated. The analysis showed differentiation of technological properties of heavy oils within the same productive layers, characterized, in turn, by heterogeneity of oil-generation and filtration-capacitive characteristics. Average oil-saturated effective thickness of the seams and the area of their oil-bearing capacity at their maximum and minimum values practically do not coincide. For most of the deposits, the density of the oil decreases with increasing bed depth and oil reservoir area, but does not depend on their average effective oil-saturated thickness. The smaller the depth of productive rocks, the more their permeability. However, the porosity of productive layers is not directly dependent on the depth of their occurrence, which indicates a complex and heterogeneous structure of reservoirs within the structural zones of the Permian system. The coincidence of these two parameters, according to the maximum values, is observed only in individual oil fields, including Ashalchinskoye and Mordovo-Karmalskoye, which is currently in experimental development, which indicates the distinctive conditions for the formation of hydrocarbon deposits in them. Clear dependences of the change in the density of the investigated oils, the content of sulfur and paraffin in them from the filtration-capacity properties of the rocks were not revealed. The main part of the oils of the investigated sediments is characterized by low paraffin content (0.07-3%). Only a clear differentiation of crude oil by technological parameters into two groups is revealed by their belonging to rocks differing in the values of the coefficient of sand content. Thus, the conducted studies have shown that the oil and bitumen formation process in the surface sediments of the sedimentary thickness of the Permian system is a region of complex phenomena occurring under the influence of difficultly controlled factors, leading to a disruption of the regular relationships between the fluid parameters under study and with parameters of sediments containing them. These features of the formation of hydrocarbon deposits of specific deposits should be taken into account when choosing the directions of geological exploration and the methods of their development.
