楚雄前陆盆地逆冲带的油气潜力

楚雄盆地位于云南省的中部 ,为一中生代的前陆盆地 ,其沉积可划分为前陆复理石和前陆磨拉石两个阶段。前陆复理石为一套半饥饿状态下的灰色 /深灰色薄层状粉砂质泥岩、泥质粉砂岩组合 ,夹泥灰岩 ,含有大量的有机质 ,为重要的烃源岩 ;前陆磨拉石为三角洲相—滨岸相的砂岩 ,为油气的储集砂体。盆地被渔泡江 三街推覆断裂切割成两部分∶西部为推覆体 ,东部为原形盆地。逆冲推覆体由根带、主逆冲带和逆冲传播前缘带三部分组成。逆冲作用始于中三叠世拉丁期 ,以前置的方式向扬子克拉通推覆 ,形成有断弯褶皱圈闭、断展褶皱圈闭、台阶状逆冲断层 岩性圈闭、基底折离圈闭和推覆带前缘传播消减带褶皱圈闭等多种类型。因而盆地逆冲带的演化对油气的聚集具有巨大的促进作用 ,因而在推覆体上寻找油气具有较好的潜力。

Petroleum potential of the thrust zone in the Chuxiong Basin,Yunnan

The Chuxiong Basin is a Mesozoic foreland basin in central Yunnan. The sediments in the basin may fall into two subtypes: foreland flysch and foreland molasse. The former is represented by grey and/or dark grey thin bedded organic rich silty mudstone and muddy siltstone associations as important source rocks intercalated with marls, while the latter consists of delta littoral sandstones as hydrocarbon reservoirs. The basin is separated by the Yupaojiang Sanjie thrust fault into two parts: the thrust nappe in the west and protobasin in the east. The thrust nappe is assembled by root zone, major thrust zone and thrust front. The thrusting may be traced back to the Ladinian (Middle Triassic) and overthrusted toward the Yangtze craton, thus resulting in the formation of fault bend trap, fault propagation trap, step thrust fault stratigraphic trap, basement detachment trap and fault fold trap in the subduction zone of the nappe front. It is clear that the thrust nappe is expected to be an important reservoir package.