柴达木盆地北缘油气分布的构造控制作用

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

该区中新生代形成了伸展构造、扭动构造、逆冲 -褶皱构造等构造样式 .早、中侏罗世形成的正断层组合构造样式 ,可形成一些小规模油气藏 .老第三纪形成的压扭性构造对油气的聚集有重要控制作用 .而新第三纪—第四纪形成的逆冲 -褶皱构造的含油气性差异很大 ,在早期断层基础上发育的逆冲 -褶皱构造有利于油气分布 ,而新形成的逆冲 -褶皱构造 ,通常不利于油气聚集 .构造应力对油气的运移聚集有重要影响 ,构造应力变化速率引起的应力驱动 ,是油气沿断层垂向运移的主要动力 ,在断层附近应力值适中、岩石扩容量较大、微裂缝发育的区域 ,是油气聚集的有利场所 .

Three kinds of structural patterns present on the northern margin of 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.