Structural styles and tectonic evolution of Cretaceous to Cenozoic faults in the Linhe Depression of Hetao Basin, China: implications for petroleum traps.

Recent breakthroughs in petroleum exploration suggest that the Linhe depression in the Hetao Basin in central and western Inner Mongolia has undergone multi-stage Meso-Cenozoic tectonic events and possesses considerable exploration potential. However, structural deformation sequences and the genesis of oil-bearing structures in the basin are still poorly understood. Analyzing the deformation sequences of structural styles can improve the understanding of the basin history and regional tectonic evolution, and is essential for targeting potential traps. In this study, we interpreted 2D seismic profiles, drilling, and well-logging data, and outcrops to elucidate structural styles, tectonic evolution, and temporal distribution characteristics of styles with the assessment of potential petroleum traps in the Linhe Depression, Hetao Basin. We identified four structural styles and sequences with fault associations in the Linhe Depression, namely, NE-striking normal faults (D₁), inversion fault-folds (D₂), NE-NNE-striking dextral strike-slip faults and normal faults (D₃), and near-E-W-striking sinistral strike-slip faults (D₄). Analysis of syn-sedimentary normal faults and the cross-cutting relationship of faults and sedimentary strata indicate that D₁, D₂, D₃, and D₄ occurred during the Early Cretaceous, Late Cretaceous to Early Eocene, Middle Eocene to Neogene, and Quaternary, respectively. The temporal development of structural styles promoted the formation, re-construction, and finalization of structural traps, while fault geometry and fluid potential influenced the dominant petroleum migration directions. It is shown that the hydrocarbon generally migrated from the northwestern sag to the southeastern slope during the peak hydrocarbon expulsion period in the Neogene. Traps of inversion anticlines and numerous fault blocks developed in the Cretaceous and Paleogene strata are identified as the most favorable trap types. The traps on the slope were produced by numerous NNE-NE-striking faults, and the dominant migration direction implies that hydrocarbons were available to fill the traps. [ABSTRACT FROM AUTHOR]