Dynamic mechanism of tectonic inversion and implications for oil–gas accumulation in the Xihu Sag, East China Sea Shelf Basin: Insights from numerical modelling

Abstract

The East China Sea Shelf Basin (ECSSB) lies at the south‐eastern margin of the Eurasian Plate and was affected by the subduction of the Pacific Plate and the Philippine Plate. It experienced and recorded multistage tectonic inversions in the Cenozoic, especially in the Xihu Sag. In an attempt to investigate the evolution and mechanism of tectonic inversion, this paper presents numerical simulation results by the finite element method to the Xihu Sag. Combined with comprehensive structural analyses of seismic profiles, this paper determines the structural geometry of the sag for establishing a viscoelastic geologic model including six‐layer strata and nine major faults. Simulation results show that the boundary conditions of transtension and transpression control the inversion process that propagates from east to west, and the distribution of low compressive stress displays certain correlations with the distribution of oil deposits. Based on quantitative analysis of the vertical displacement field of the Xihu Sag, this paper identifies a tectonic inversion process, which indicates that the western part of the sag uplifts and the eastern part subsides during the first‐stage inversion; whereas the western part subsides and central‐eastern parts uplift during the second and third stages. The formation of the tectonic inversion is controlled by the adjustment of the stress field from dextral transtension to sinistral transpression caused by the change of subduction rates and direction of the Pacific Plate and the Philippine Sea Plate.

Controls of the Sandbody Scale and Fault Throw on the Lithology and Composite Reservoir Formation in the Baoyunting Slope, East China Sea

“…The Xihu Depression is located in the northwestern East China Sea Shelf Basin, which is adjacent to the convergence zone of the Pacific Plate, Philippine Plate, and Eurasian Plate [8][9][10][11][12][13] (Figure 1). The fundamental structure of the basin was established during the Keelung movement that occurred in the early and middle Mesozoic eras in the East China Sea Shelf Basin.…”

Central China Orogen along the Silk Road (Part 2): Mineral deposits, hydrocarbons, geohazards, and environments

“…In the paper by Dang et al (), Triassic regional structural fractures in the Ordos Basin are considered significant in understanding the migration and accumulation of oil and gas, and development of low permeability oil–gas intervals. Hu et al () have used numerical modelling to determine the dynamic mechanism of tectonic inversion in the Xihu Sag, East China Sea Shelf Basin, and assessed the implications for oil–gas accumulation. In a companion paper by Z. Liu, Dai, et al (), thermo‐mechanical modelling was employed to ascertain the effect of Mesozoic magmatic activity and tectonic evolution in the southern East China Sea Continental Shelf Basin.…”