STRUCTURAL CONTROLS OF PETROLEUM AND GASDISTRIBUTION ON NORTHERN MARGIN OF QAIDAM BASIN, CHINA

doi:10.3321/j.issn:1000-2383.2001.01.009

Abstract：Three kinds of structural patterns present on the northern marginof the Qaidam basin in the Mesozoic and Cenozoic are shown in this paper as follows: the extensional structure, the torsional structure, and the thrust-fold structure. The structural pattern of the normal fault assemblage that occurred in the Early and Middle Jurassic may have initiated some small-scale petroleum and gas pools. The compressive torsional structure that occurred in the Early Tertiary may have controlled the accumulation of petroleum and gas. However, the petroleum and gas-bearing properties vary greatly in the thrust-fold structure that occurred in the Late Tertiary-Quaternary. The thrust-fold structure that have developed from the early fault is favorable for the distribution of petroleum and gas. On the other side, the newly-formed thrust-fold structure is usually not favorable for the accumulation of petroleum and gas. The structural stress has an important effect on the migration and accumulation of petroleum and gas. The stress caused by the change in the structural stress rate is the main driving force for the vertical migration of the petroleum and gas along the fault. Near the fault, the stress value is moderately medium, the lithological dilation is relatively great, and the micro-cracks develop well. Such a region is favorable for the accumulation of petroleum and gas.