Dolomitization in the Upper Paleozoic succession of the north-Ostaninsk field, Nyurolsk Basin, Western Siberia: Implications for hydrocarbon exploration

Abstract

Paleozoic rocks in Western Siberia may contain significant hydrocarbon resources. However, effective methods for their exploration are poorly constrained. This study provides new insights into the causes of reservoir formation using the upper part of the Paleozoic succession of the North-Ostaninsk field in the Nyurolsk Basin as a case study. The carbonate rocks have been affected by dolomitization. Four dolomite generations have been identified: Floating in the matrix (D1), fracture-filling (D2.1), stylolite-associated (D2.2), partly replacive (D3) and, pervasive (D4). The last one replaces biogenic limestone in the upper part of the Paleozoic succession and coincides with the presence of a reservoir in the field. A systematic analysis petrographic, fluid inclusion, and carbon and oxygen isotope investigations suggest that the origin of dolomite is from the downward infiltration of meteoric water with higher Mg2+ and Fe2+ derived from the alteration of tuffaceous materials. The results, along with values of the magnetic field anomaly, reveal the relationship between dolomitization and the distribution of the oil and gas reserves in this Paleozoic succession within the basement of the West Siberian Basin. This new insight may be used to predict similar accumulations in poorly explored territories.