Evaluation of the hydrocarbon system of Qom formation in the North of Dasht-e-Kavir, Central Iran

The Oligocene-Early Miocene Qom Formation in Central Iran, recognized as both a hydrocarbon reservoir and a primary source rock. To evaluate the hydrocarbon potential and reconstruct the depositional environment of the Qom Formation, four sections (section 1, section 2, section 3, and section 4) and three wells in the north of the Dasht-e-Kavir have been selected. Field observations and microscopic analysis revealed that the Qom Formation was deposited in a diverse range of sedimentary environment within an open carbonate shelf environment. This included four distinct facies belts: tidal flat, lagoon, shoal/reef, and platform slope. Rock-Eval pyrolysis and one-dimensional modeling of three wells were employed to assess the source rock potential of the Qom Formation. Results indicate that the E member in the central part of the study area is in a better condition compared to other intervals and area. The C3 sub-member in the central part was also identified as a potential source rock, albeit with lower hydrocarbon generation and expulsion potential. Microscopic analysis of the C4 and F members revealed abundant grain-supported facies and reefal structures, indicative of high-energy depositional environments. These facies exhibit various types of porosity and fractures, suggesting favorable reservoir rock characteristics. The C2 and D members exhibit lithological characteristics of effective cap rocks. Additionally, the marls associated with the platform slope of the C1 sub-member exhibit source rock potential in the central and eastern sections (section 3 and section 4), while the lower and upper parts of the C1 sub-member in the western sections (section 1 and section 2) may serve as potential reservoir rocks. The Qom Formation was deposited in the northern area of the Dasht-e-Kavir during the regression and relatively low sea level. Our study showed that the central part of the studied area has a suitable hydrocarbon system.