Comprehensive classification of Red-colored Serie rocks from the eastern flank of the South Caspian Basin (Jigalybek field) based on reservoir and geophysical properties

The Absheron-Prebalkhanian tectonic zone, known as the Absheron threshold, has been the subject of extensive study by researchers for nearly hundred years. This region holds significant interest due to its strategic location between the well-known oil and gas-bearing areas of Absheron and Cheleken. This paper presents a comprehensive classification of Red-colored Serie (RCS) rocks from the Jigalybek (Jdanov Bank) field (located in the eastern part of the South Caspian Basin) based on reservoir and geophysical properties. The study includes a detailed analysis and classification of rocks into different classes, considering both reservoir and non-reservoir properties. A total of 42 core samples were analyzed to determine key geophysical parameters, including R-1-R-5, ρLL, SP, ΔJγ, ΔJpγ, and Δd. The analysis revealed four distinct classes of rocks based on their reservoir properties, identifying two types of highly permeable and moderately permeable reservoirs, and two types of non-reservoirs comprising compacted low-permeability clays and pure clays. The geophysical classification further differentiated the rocks into oil-bearing, water-bearing, and non-reservoir types, emphasizing the geophysical signatures that distinguish between these categories. A comprehensive classification approach was also applied, combining six reservoir properties and ten geophysical parameters to refine the distinction between water-saturated and oil-saturated reservoirs. The study demonstrated that water-saturated reservoirs are generally more clay-rich and less porous than oil-saturated reservoirs, providing a robust methodology for identifying and characterizing different types of reservoirs in the field. Such a classification system is valuable for improving the accuracy of reservoir identification and characterization, leading to better resource management and extraction strategies in the Jigalybek field. The results underscore the importance of integrating multiple geophysical and reservoir parameters to achieve a more precise classification and understanding of subsurface rock properties.