Discrete element method simulation of the fold-and-thrust belts along strike various compression in the southern margin of the Junggar Basin, China

Abstract

The fold-and-thrust belts developed in the southern margin of the Junggar Basin in China can be divided into different segments and oblique rows in the strike and dip direction respectively. The internal structural patterns and linkage types of different sub-segments usually affect the oil and gas accumulation. In this work, we study on the propagation and linkages of the structural patterns involved in the fold-and-thrust belts due to the differential compression by the Discrete element method (DEM). Two simulations are configured to use four velocity modules, which can move with different velocity at the same time: (i) the homogenous module filled with brittle simulating sediment is used to investigate the structural response to a velocity difference and (ii) the module with ductile detachment at the front of each module is used to test how the weak layer affects deformation. The results are illustrated by topography of the simulations, such as cross sections perpendicular and parallel to the shortening direction, forward and lateral displacements seen from the top view, and sections of the velocity field. The results show that (i) resistance from adjacent modules promotes the development of back-thrusts in faster modules, and drag from faster moving module hinders nucleation in slower modules, and (ii) two types of transfer zones caused by shear stress appear in the piedmont region and in front of the fold belts. The detachment simulation produces results are similar to the western segment of the southern margin of the Junggar Basin, which can explain the several rows of anticlines that appear oblique in the plane. These results are useful to analyze the formation process of the oil and gas trap developed in the similar compressional area.