104 / 2022-02-15 11:12:34

Effect of fault reactivation on palaeogeographic restoration and formation of high-quality source rocks in the western Qaidam Basin, Tibet Plateau

fault,Tibet Plateau,source rock,Qaidam Basin,saline lacustrine,inversion structure

Fault reactivation study is significant to basin evolution and palaeoenvironment and palaeogeographic analysis. Balanced geological profile method was proposed to restore fault historical reactivation in this paper. This method can take into account important information such as differential compaction and strata erosion thickness. Meanwhile, it can directly measure the slippage of faults by fault reactivation intensity curve, especially it has important application value in identifying the direction of fault reactivation in a specific geological history period, which is the further development and improvement of traditional fault reactivation analysis method. The fault reactivation characteristic in the western Qaidam basin was analyzed by this method, two episodes of structure inversion were identified. The first episode was converted from the squeezing environment in the late Mesozoic to the extensional tectonic environment in the Paleogene of the Cenozoic. The second phase is the deposition period of the Shangganchaigou Formation (N₁) from the extensional tectonic background to compressional tectonic background. The extensional tectonic background of the sedimentary period of the upper Xiaganchaigou Formation (E₃²) controlled the development of high-quality source rocks. After the depositional period of the Shangganchaigou Formation, the Qaidam Basin was converted into an compressional tectonic background, which controlled the traps forming, capturing hydrocarbons formed at a later stage. Inversion structures near faults can form early traps and have the potential to capture low-mature hydrocarbons generated early, and are promising plays for deep petroleum exploration.