Facies analyses and depositional setting of the Lower Cretaceous Shurijeh–Shatlyk formations in the Kopeh Dagh–Amu Darya Basin (Iran and Turkmenistan)

Abstract

The Lower Cretaceous siliciclastic fluvial to shallow marine Shurijeh-Shatlyk formations together form one of the main reservoir successions in the Kopeh Dagh-Amu Darya Basin (NE Iran, Turkmenistan, and north of Afghanistan). Sedimentary facies and thickness changes in the Shurijeh-Shatlyk formations show complex variations throughout the basin, which highlight the importance of understanding the controlling factors on facies distribution and depositional setting for future hydrocarbon exploration. Integration of 3D seismic data, 13 boreholes, and five surface stratigraphic sections led to identification of lithofacies and facies associations. The results allow subdivision of this siliciclastic succession into four stratigraphic units (A, B, C, and D). Our study indicates that base-level changes interacted with palaeotopography inherited from Middle Jurassic basin rifting, Upper Jurassic carbonate reefs/patch reef distributions, and reactivation of the deep basin faults, to control the Shurijeh-Shatlyk depositional setting and sedimentary facies distribution. Our findings show that the Aghdarband and Badkhyz-Maimana palaeo-highs affected the Kopeh Dagh-Amu Darya Basin throughout deposition of the Shurijeh-Shatlyk formations. Allogeneic processes and active tectonics, related to the Valanginian Late Cimmerian Orogeny, caused a base-level fall, exposure of Upper Jurassic carbonate sediments, and deposition of a carbonate pebbly conglomerate unit in the western part of the study area. This base-level fall led to the deposition of thick evaporites in the western area and conglomerate in the eastern parts of the Kopeh Dagh. Due to a Hauterivian sea-/ base-level rise, several deltas formed in the basin, which form the main reservoir zone in the Murgab Depression and Khangiran Field in Turkmenistan and Iran.

Carbonate platform evolution of the Tirgan formation during Early Cretaceous (Urgonian) in the eastern Kopet-Dagh Basin, northeast Iran: depositional environment and sequence stratigraphic significance

“…During the Late Cimmerian Orogeny, the non-marine Shurijeh formation deposited in a fluvial setting in the eastern basin and to the west changed gradually to argillaceous calcareous and carbonates marine succession of the Zard formation (Moussavi-Harami and Brenner 1993;Hosseinyar et al 2018). With transgression of the Cretaceous sea (late Hauterivian) in central, northwest parts of Kopet Dagh Basin, a thick sequence of carbonate facies of Tirgan formation was deposited extensively (Haq et al 1987;Haq 2014) that represents one of the Urgonian carbonate platforms.…”

“…2c). In the study areas of this formation overlies Shurijeh formation, a fluvial succession (Moussavi-Harami and Brenner 1990;Hosseinyar et al 2018), and is overlain by Sarcheshmeh formation consists of ammonite bearing shale and marl (Afshar-Harb 1979). In central Kopet-Dagh Basin, the Tirgan formation belongs to the upper Barremian through the lower Aptian interval (Afshar-Harb 1979;Immel et al 1997;Carevic et al 2013;Taherpour Khalil Abad et al 2013).…”

Types and Distribution Characteristics of Callovian-Oxfordian Reservoir on the Right Bank of Amu Darya River in Turkmenistan

“…The Amu Darya Basin in Turkmenistan is an important oil-gas-bearing basin in the world [1][2][3][4], in which the middle-upper Jurassic Callovian-Oxfordian limestone is a key oil-gas-bearing reservoir [5,6], with proven gas reserves of about 22 trillion cubic meters and remaining gas resources of about 20 trillion cubic meters. Thus, how to effectively explore and develop these oil and gas resources has become a crucial target of oil geologists worldwide.…”