Recovery of the Cretaceous palaeo‐uplifts and its implications for hydrocarbon systems in the Kuqa Depression, Tarim Basin, western China

Abstract

The Kuqa Depression is an important oil and gas exploration area in the Tarim Basin, and exploration practices indicate that the gas reservoirs such as Dabei, Kela, and Keshenare distributed in the Cretaceous palaeo‐uplift area. However, few studies have been done on the Cretaceous palaeo‐uplifts. On the basis of the logging gamma curve, the spectrum analysis of the Bashijiqike Formation shows that the sedimentation of the Lower Cretaceous stratum was controlled by the Milankovitch cycles. As the stratum exhibits the characteristic Milankovitch periodicities, 133, 124, 100, and 95 ka eccentricity, 46.5 and 36.6 ka obliquity, and 22.2 ka precession periods are identified in the residual Bashijiqike Formation. By combining the results of cyclic analysis and thermal simulation of apatite fission track (AFT), the stratum denudation amount of Dabei‐Tubei palaeo‐uplift and Kelasu palaeo‐uplift in the Late Cretaceous was calculated, and the palaeo‐uplifts were restored. The results show that the original thickness of the Cretaceous stratum in the core of the Dabei‐Tubei palaeo‐uplift was ~1,500 m and was more than 1,800 m in the core of the Kelasu palaeo‐uplift. The AFT modelling results indicate that there were two cooling phases in provenance, that is, since the Late Triassic–Early Jurassic (ca. 200 Ma) and the Late Jurassic–Early Cretaceous (ca. 160–130 Ma). In addition, the depositional area also experienced two cooling phases, namely, since the Late Cretaceous (ca. 110–60 Ma) and the Late Palaeogene–Early Neogene (ca. 20 Ma).