Raw material base of Russia’s unconventional oil and gas reserves (hydrocarbons shale strata)

Abstract

One of the most controversial and discussed issues related to the development of the hydrocarbon raw material base in recent years is the issue of exploring the possibilities of involvement in industrial development accumulations associated with high-carbon shale complexes that are widespread in Russia. Interest therein is supported by the system of benefits provided by the Government for low-permeability reservoirs and special preferential conditions for geological exploration provided to subsurface users in recent years. An important effect was also achieved by developing a methodology for reserves assessment and placing on the state balance a whole series of fields with oil deposits in the Domanik formation of the Volga-Ural oil and gas province (OGP). Simultaneously, the assessment of the potential of high-carbon formations in the Russian Federation mainly continues to be the subject of scientific research without an applied component, due to its inapplicability for selecting both the most significant areas for exploration and the possibilities of using it to justify investments. Here, the uncertainty is related to the estimation of possible production levels with an unclear correlation between development technologies, filtration and reservoir properties, and the potential of high-carbon strata. This study discusses two approaches that allow assessment of the potential of the main high-carbon strata distributed in Russia.

Potential of High-Carbon Domanik (Upper Devonian) Shale Deposits: Timan-Pechora Oil and Gas Province Assessment

“…At the same time, the total amount of oil in the free pore space of the domanik horizon using kinetic spectra amounted to 10.5 billion tons of oil and 6.3 trillion m 3 of gas, and taking into account the reservoir space defined with the division into the shelf zone, the slopes of the carbonate platform (side parts of the depression) and in the de-pressions is 5.2 billion tons of o.e. in the areas of high concentration, which is comparable to the volume of accumulated HC in traditional reservoirs, estimated in TP about (6 billion tons) and allows to consider the high-carbon domanik strata as an important reserve for oil production in the conditions of high prices for hydrocarbons in the well-developed regions of the European part of Russia (8,11).…”

“…The estimation of the proportion of syngenetic and epigenetic bituminous in the generation thickness was compared with the effective porosity, i.e. a combined volume method and an improved volume-genetic method were used (Table 3, Figure 19) (8).…”

“…This formation is characterized by a high content of organic matter (OM) of marine genesis (TOC reaches 25%), the catagenetic maturity of which varies from proto (PС) -to apocatagenesis (AC) (7)(8)(9)(10)(11) depending on the paleogeological conditions.…”

Theoretical and methodological approaches to identifying deep accumulations of oil and gas in oil and gas basins of the Russian Federation

“…In the Dzungarian basin, a fairly low geothermal gradient is observed in a number of wells in the central part of the basin (2.0 °C-2.3 °C/100 m), and accordingly, conditions for the formation of oil have been preserved at depths up to 6 km, and condensate at deeper depths. Thus, in the work (Prischepa et al, 2022), a pattern of decreasing the density of crude oil with depth was revealed (at a depth of <3,100 m-average density oil 0.84-0.9 g/cm 3 , at a depth of 3,100-3,900 m-light oil 0.8-0.82 g/cm 3 , and below 4,400 m-mainly condensate. An important pattern is noted in the distribution of gas in the central part of the Dzungarian basin.…”

Hydrocarbon Generation and Residue Features of Ediacaran High-Maturity Source Rocks and Their Significance in Gas Exploration in Sichuan Basin

“…The potential of shale oil and gas resources within these rocks is determined via residual hydrocarbons [16]. The assessment of residual hydrocarbons plays a crucial role in evaluating shale oil and gas resources and selecting exploration prospects [17][18][19]. Previous studies suggest that the Ediacaran Dengying Fm acted as a reservoir in the Sichuan Basin.…”