Lithological and geochemical features of potentially oil source Upper Paleozoic rocks of the eastern side of the Pre-Caspian basin

UDK: 553.98
DOI: 10.24887/0028-2448-2023-5-31-35
Key words: source rock, organic matter, maturity of organic matter, types of kerogen, Rock-Eval method
Authors: A.S. Rakhmatullina (Gubkin University, RF, Moscow), D.O. Almazov (VNIIneft JSC, RF, Moscow), A.S. Monakova (Gubkin University, RF, Moscow), S.F. Khafizov (Gubkin University, RF, Moscow), K.I. Dantsova (Gubkin University, RF, Moscow)

The article presents the lithological and geochemical characteristics of potential oil source rocks on the example of one of the wells on the eastern side of the Caspian depression. According to the complex of geological and geophysical data, several large strata were identified, lithotypes enriched in organic matter (OM) were selected based on core and pyrolytic data. Structural-textural and mineral-material features of rocks largely determine the nature of organic matter distribution. The authors presented a detailed lithological description of various lithotypes, determined the amount and patterns of distribution of organic matter, maturity level and, as a result, the oil source potential of a particular rock. The article introduces a detailed lithological description of the section of one of the deep wells of the pre-salt complex of the Upper Paleozoic. Due to a detailed study of the core material, characteristics that allowed making an assumption about attributing of certain strata to potential oil source intervals were determined.

The study of rocks was conducted by optical microscopy with the identification and description of lithotypes, with special attention paid to the nature of the distribution of organic matter in the rock. The Rock-Eval method was used to determine the generation potential of the rocks. The article presents data on the main geochemical parameters - the total organic carbon in the rock, the hydrogen index and the temperature corresponding to the maximum yield of hydrocarbons in the S2 peak (the residual generation potential of the rock). As a result, the classes of oil source rocks, the type of kerogen and the stage of maturity of organic matter were measured.

The results can be correlated with the intervals of occurrence of rocks of similar lithotypes in the similar strata in the wells section that were not characterized by a core.


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