Geochemical investigation of oils from Cretaceous to Eocene sedimentary sequences of the Abadan Plain, Southwest Iran

Stratigraphy, Tectonics and Hydrocarbon Habitat of the Abadan Plain Basin: A Geological Review of a Prolific Middle Eastern Hydrocarbon Province

“…As such, the basin is believed to be extended towards the northern margin of the Persian Gulf, covering some of the offshore fields as well (Figure 2; [9,23]). The north-west end of the Persian Gulf is often considered as a part of the Abadan Plain Basin [9,23], and due to hydrodynamic connections between some structures on both sides of the border, this definition of the basin covers a narrow margin in the south of Iraq (Figure 2). area has also been defined by Moallemi and Kermanshah [22] for this basin which covers almost all areas of Kuwait and northern Persian Gulf extending towards Saudi Arabia.…”

“…Analyzing oil samples from different reservoirs of the Abadan Plain Basin by Alizadeh, et al [23] reveals that low concentrations of normal alkane (ranging 6-18) contribute to the relatively high values of C17/C27 (ranging 3.8-6.21), suggesting that hydrocarbons were derived from marine organic matter [65,66]. Chemical attributes of the oil samples also indicate the conditions in which the sediments were deposited.…”

“…Concurrently, high abundance of C21 and C22 pregnanes is a key indicator of a hypersaline depositional environment, and further indicates that the oil formed in association with carbonate rocks [71,72]. Alizadeh, et al [23] showed that the presence of C21 and C22 pregnanes is predominantly controlled by environmental and source factors such as lithology, marine organic matter and salinity. Therefore, identified the depositional environment of the oil source in the Abadan Plain Basin as an anoxic marine carbonate environment with free H 2 S.…”

“…Pabdeh, Kazhdumi and Gadvan source rocks are in the oil expulsion phase, and the Garau Formation source rock is currently at the beginning of gas expulsion [18]. According to the oil samples tested by Alizadeh, et al [23], the Lower Cretaceous (Kazhdumi, Gadvan and Fahliyan) reservoirs have higher thermal maturity (higher API and lower concentration of aromatics) than shallower reservoirs. Hence, it is expected that while the formations become tighter (low porosity and permeability) with increasing depth, deeper explorations would be expected to encounter natural gas or light oil hydrocarbons.…”

“…There is another prospect beyond the depth interval of this research that includes Carboniferous/Permian source rocks, and accumulations in the Dehram Formation (Permian period), with the source rock possibly at the gas expulsion phase; hence, it is an interesting subject for further explorations. Similarly, the hydrocarbon expulsion capability of the Silurian shales has been identified [73][74][75][76][77][78], and therefore, the Devonian sandstone may also be considered as a potential reservoir rock [23,76,79] and could be a possible target for further explorations.…”