苏里格气田下石盒子组层序地层学与天然气高产富集区分布规律

苏里格气田下石盒子组气藏为典型的岩性气藏，其分布主要受岩性控制，具有较强的隐蔽性。为了查明气藏分布规律，研究了下石盒子组层序地层格架及其储集砂体的叠置与分布规律。在下石盒子组内部识别出1个重要的不整合面，发现在层序地层格架内，不整合面之下发育基准面下降期的三角洲前积体，不整合面之上发育基准面上升期的下切谷充填河道砂体。下切谷越过不整合面向下切入三角洲前积体，下切谷充填河道砂体与三角洲前积体连通并叠置，使三角洲前积体成为天然气的重要输导层和储集层，进而为下伏气源岩生成的天然气向上运移提供了通道，使得三角洲前积体与谷地充填河道砂体的叠置区成为天然气富集高产的有利部位。图7表1参12

Sequence stratigraphy and the distribution of natural gas enrichment and high production area in Lower Shihezi Formation, Sulige gas field, Ordos Basin

The gas reservoirs in the Lower Shihezi Formation of Sulige gas field are typical lithological reservoirs. They are very subtle and controlled by lithology. In order to reveal the gas reservoirs distribution rule, the sequence stratigraphy and reservoirs overlap and distribution of Lower Shihezi Formation were studied. A key sequence boundary which is an unconformity is recognized in the formation. Below the unconformity are the prograding lobes of fluvial delta which were developed during the base-level fall. Above the unconformity is the incised valley-filled channel sandbodies developed during the base-level rise. The incised valley cut downward into the prograding lobes of fluvial delta, and the incised valley-filled channel sandbodies overlapped over the prograding delta sandbodies, The prograding lobes of fluvial delta acted as the main channels for hydrocarbon migrating from the lower source rocks to the upper incised valley-filled channel sandbodies. The favorable gas accumulation areas and the promising gas production areas lie on the overlapping sites of the incised-valley- filled channels and the prograding delta.