关键词: 青藏高原, 特提斯域, 盆地, 油气条件, 勘探方向

Abstract:

Qingzang Plateau is an important part of Tethys domain between paleo-Eurasia and Gandwana. The petroleum geological condition there is complicated due to the regional framework of nearly E-W trending arc faults alternated with faulted terrains, the complex crust-mantle architecture and intensive neotectonic movements within the plateau. Since Cambrian, the plateau has undergone multi-cyclic geological evolution of four major stages: Proterozoic ocean, palaeo-Tethys, new Tethys and indian Ocean. The composition and overlapping of the prototype basins in different places and different periods within the plateau formed potential oil-bearing regions. Among them, Northern Himalaya is composed of overlapped cratonic depression-intercontinental rift-passive continental margin-peripherral foreland basin: the Northern Gangdise is composed of superposed cratonic rift depression-back arc basin-remnant back are basin-strike slip pull apart basin : Northern and Southern Qiangtang consist of superimposed cratonic rift depression-quasipassive continental margin-strike slip and compressional basin, and cratonic depression-passive continental margin-peripheral foreland basin and strike slip basin respectively. On the setting of intensive compressional deformation and uplifting,the basins show unique stratigraphic distribution,tectonic framework and structural patterns,and complex oil-gas-water system. Various blocks in the plateau have multiset of source rocks and reservoirs, but the organic matter of the source rocks is a little overmatured. As the plateau uplifted, the period of high geothermal environment was little later than that of tectonic deformation. This might probably result in secondary oil generation and late stage pooling in some places within the plateau. Mudstones and shales that widely developed there, gypsolyte distributed in local places and permafrost formed multi-type of source-reservoir-cap rock assemblages. Different types of structural, lithologic and sedimentary traps are targets for oil and gas exploration. Strategic break-through in oil and gas exploration could be achieved by selecting stable blocks with fine oil-gas-water system and overlapped basins with favourable matching within the plateau.