Lithofacies types, reservoir characteristics, and hydrocarbon potential of the lacustrine organic-rich fine-grained rocks affected by tephra of the permian Lucaogou formation, Santanghu basin, western China

Pore structure and oil‐bearing property of laminated and massive shale of Lucaogou Formation in Malang Sag, Santanghu Basin

“…Since the late Palaeozoic, the Santanghu Basin was mainly transformed by the late Hercynian and Late Yanshanian tectonic movements, and the residual basin of Permian age was superimposed with the Mesozoic depression basin, forming a small, superimposed basin (Liang et al, 2019;Liu et al, 2020). The Malang Sag is located in the F I G U R E 1 Location of Malang Sag in the Santanghu Basin (a) and lithological sketch of Permian strata (b) (modified after Pan et al, 2022). southwest of Santanghu Basin, covering an area of approximately 1500 km 2 , which is one of the important hydrocarbon-rich depressions (Liang et al, 2019;Liu et al, 2020;Pan et al, 2022).…”

“…The Malang Sag is located in the F I G U R E 1 Location of Malang Sag in the Santanghu Basin (a) and lithological sketch of Permian strata (b) (modified after Pan et al, 2022). southwest of Santanghu Basin, covering an area of approximately 1500 km 2 , which is one of the important hydrocarbon-rich depressions (Liang et al, 2019;Liu et al, 2020;Pan et al, 2022). The Malang Sag is characterized by well-developed strata, with the maximum thickness of thousands of meters in the middle Permian, which can be divided into Lucaogou Formation (P 2 l) and Tiaohu Formation (P 2 t), from bottom to top.…”

“…During the deposition of the Lucaogou Formation, volcanism was relatively active, and a set of lacustrine fine-grained sedimentary formations with complex lithology were deposited in Malang Sag. The second member of the Lucaogou Formation (P 2 l 2 ), with a thickness of 200-400 m, is the main object for the exploration and development of shale oil (Pan et al, 2020(Pan et al, , 2022.…”

“…(Ma et al, 2015;Zhao et al, 2009). During the depositional period of Lucaogou Formation in Santanghu Basin, the volcanic activity was frequent, and the volcanic ash entered the lake basin through falling or the transportation from water (Liu et al, 2020;Pan et al, 2020Pan et al, , 2022. Without or less transportation process, the clastic and lithic chips can directly support each other, which makes the original porosity and the connectivity of pores relatively good, it also provides convenient conditions for the water to release the vitrification and the dissolution of organic acids in the later stage.…”

“…There is a set of continental shales that is rich in tuffaceous sediments in Permian Lucaogou Formation in the Santanghu Basin in China. In this region, the sedimentary organic matter (OM) is abundant, while clay mineral content is poor, and organic matter is in a layered symbiosis with tuffaceous matter (Liang et al, 2019;Liu et al, 2019;Liu et al, 2020;Pan et al, 2020Pan et al, , 2022Wang et al, 2013). These volcanic materials, terrigenous debris, and organic matter form laminar structures and massive structures, which have different effects on the quality of shale reservoir and the mobility of shale oil.…”