Architecture of basin-mountain systems and their influences on gas distribution: A case study from the Sichuan basin, South China

Abstract

The basin-mountain systems in the Sichuan basin exert major control on today’s oil/gas distribution, chiefly through their controlling influence on petroleum reservoirs preservation, the thickness of deposited terrestrial formations and degree of uplift and denudation. The composite basin-mountain system in the Sichuan basin and its peripheral mountains can be classified as two types – margin-plate systems and interior-plate systems. The margin-plate basin-mountain systems include the Sichuan basin and its surrounding Longmen Mountains, Micang Mountains and Daba Mountains, which are not only the western and northern marginal area of the Sichuan basin, but also represent the western margin of the Yangtze plate (South China Block). The margin-plate basin-mountain systems, with binary units of large-scale thrust belts and foreland basins, have different deep lithospheric structures, abrupt boundaries and great contrast in today’s geomorphology between the basin and the mountains. On the contrary, the interior-plate basin-mountain systems comprised by the Sichuan basin and its adjacent interior-plate Qiyue Mountains, Dalou Mountains and Daliang Mountains; represent the eastern and southern marginal area of the Sichuan basin located within the Yangtze plate. They have similar lithospheric structure and gradual boundaries between the basin and the adjacent mountains, lacking foreland basins. Today’s medium-large scale natural gas accumulations in the Sichuan basin are mainly distributed in the areas influenced by the margin-plate basin-mountain systems, and are located especially in the foreland basins.