Lower Cretaceous source rock evaluation and thermal maturity evolution of the Chagan depression, Inner Mongolia, Northern China

Abstract

The Chagan depression has the greatest oil and gas exploration potential in the Yingen-Ejinaqi Basin, Inner Mongolia, northern China. In this paper, source rocks are evaluated and the thermal maturity evolution of typical wells and the primary source rocks is modeled using BasinMod 1D and Basinview software provided by Platte River Associates, Inc. The results show that the Chagan depression developed three sets of source rocks, including the Baiyingebi 1 and 2 Formations and Suhongtu 1 Formation. The Baiyingebi 2 Formation has been the most important source rock in the Chagan depression, dominated by the medium to high maturity source rocks with type II kerogen. This study also reveals that the thermal maturity evolution of source rocks is controlled by the paleogeothermal fields during the Yingen Formation depositional periods when the maximum maturity was reached. The Bayingebi 1 and 2 Formations both experienced the hydrocarbon generation peak and reached the medium to over mature stage. While the Suhongtu 1 Formation has only reached the low to medium mature stage with lower hydrocarbon generation potential. In addition, the source rocks thermal maturity evolution in the West sag is superior to that in the East sag. Therefore, the Bayingebi 2 Formation should be investigated for the oil exploration, and the Wuliji fault nose structural zone and central structural zone will remain the primary targets for the next exploration.

Terrestrial heat flow and lithospheric thermal structure in the Chagan Depression of the Yingen‐Ejinaqi Basin, north central China

“…Influenced by multistage tectonic movements with the Late Hercynian, Indosinian, Yanshanian and Himalayan orogenies (Fu et al, 2016; Meng, Hu, Jin, Zhang, & Xu, 2003; Li, Wilde, Wang, Xiao, & Guo, 2016; Han 2017; Lu et al, 2017; Zuo et al, 2017), the YE Basin went through the following stages. (a) A strong tectonic activation stage from the Late Silurian to the Early‐Middle Devonian, when the southward subduction of the Mongolian Oceanic Plate and the collision between the Siberian Block and the North China Craton resulted in the closure of the Paleo‐Asian Ocean, with the formation of the YE Basin in an intracontinental rift or rift basin (Lu et al, 2017).…”

“…The Paleozoic strata in the YE Basin mainly include the Carboniferous and Permian, mainly distributed in the Ejinaqi—Wutaohai area with a residual thickness of 1,500–2,500 m (Liu, Shen, & Chen, 2011). The Triassic and Jurassic strata occur only in a few subbasins (Liu et al, 2011; Lu et al, 2017; Zhang et al, 2014; Zuo et al, 2017). The Lower Cretaceous strata show the maximum thickness and is the most widely represented stratigraphic unit within the basin, reaching 2,000–3,500 m and locally to more than 4,000 m (Liu et al, 2011; Lu et al, 2017; Niu et al, 2018; Zhang et al, 2014; Zuo et al, 2017).…”

“…The Chagan Depression is located in the central Chagandelesu subbasin in the eastern YE Basin (Figure 2). It is a Cretaceous rift basin on the folded Late Paleozoic basement (Wang, Shi, Zhang, & Qi, 2016; Zuo et al, 2017). The Chagan Depression experienced multiple and diverse tectonic activities.…”

“…The thermal lithospheric structure refers to the proportion of the heat flow in the crust and the mantle, and their competency and structural relationship (Blackwell, 1971; Wang, 2015). The crust‐mantle heat flow distribution affects the current crustal and mantle activity, deep temperature conditions, and the formation of basins and mountains (Artemieva, 2018; Artemieva & Mooney, 2001; Dalton et al, 2017; Goodge, 2018; Majorowicz et al, 2019; Norden, Förster, & Balling, 2008; Rudnick & Nyblade, 1999; Wang, 2015), and is an important window to understand the tectonic evolution of the lithosphere and the deep dynamics of basins (Hu et al, 2001; Mareschal & Jaupart, 2004; Björk & Winsosr, 2006; Artemieva, 2006; Zuo et al, 2013; Zuo, Li, Li, & Hao, 2015; Zuo, Song, Li, Wang, & Yang, 2017; Gong, Zhang, & Ye, 2011; Qiu et al, 2014; Li, Zuo, Qiu, & Gao, 2017; Liu, Zhang, Zhang, & He, 2016; Jiang et al, 2019).…”

Source rocks evaluation of the Paleogene Shahejie 3 Formation in the Dongpu Depression, Bohai Bay Basin

“…In addition, observations can only be obtained on the source rock maturity at the present day, other than the source rock thermal maturity history and the associated hydrocarbon generation and expulsion, migration, and accumulation histories that help understand the entire process from petroleum generation to accumulation. With the development of modeling technology, the source rock thermal maturity history and time and space distribution in sedimentary basins can be quantitatively determined by basin simulation, and the basin simulation method is used in the study of source rock thermal maturity history in many basins (Belaid et al, 2010;Berthonneau et al, 2016;El-Shahat et al, 2009;Gonza´lez et al, 2013;Hakimi and Ahmed, 2016;Hu et al, 2001;Hudson and Hanson, 2010;Qiu et al, 2012Qiu et al, , 2010Zeinalzadeh et al, 2015;Zhu et al, 2016;Zuo et al, 2011Zuo et al, , 2014Zuo et al, , 2015bZuo et al, , 2015aZuo et al, , 2017aZuo et al, , 2016aZuo et al, , 2016b.…”