苏里格地区盒8段天然气充注成藏机理与成藏模式探讨

The Discussion of Mechanism and Pattern of Hydrocarbon Accumulation of Gas-filling in Sulige Region of the 8 Member of Xiashihezi Formation

二叠系下石盒子组盒8段是鄂尔多斯盆地苏里格气田的主力产层。盒8段属于辫状河沉积体系,砂体分布类型主要呈透镜状和复合条带状。根据毛细管压力曲线,估算出3类储层天然气浮力驱动需要克服的毛细管阻力和相应的临界气柱高度。由于苏里格地区的区域构造平缓,盒8段储层天然气聚集成藏的驱动方式主要受储层砂体分布范围和储层物性控制。透镜状砂体的分布范围较小,孔渗条件较差,天然气在砂体中聚集依靠气体膨胀驱动。复合条带状砂体虽然分布范围大,储层物性相对较好,但是非均质性强,气体膨胀和浮力共同驱动天然气聚集成藏。

The 8 member of the Permian Xiashihezi Formation was the main gas producing layer of Sulige Gas Field in Ordos Basin.It belonged to a braided fluvial depositional system,the type of sand body distribution was mainly the lenticular structure and composite strips.Based on the curve of capillary pressure ,the capillary drag that should be avoided for buoyancy driving and height of critical gas column were estimated for 3 types of reservoirs. Because of the gentle areal structure,the types of gas accumulation were mainly controlled by sand body distribution and reservoir properties.The distribution area of lenticular sand body was relatively small with poor porosity and permeability,gas accumulation in the sand body depended on driving by gas expansion.Although compound strips sand bodies are distributed in a large area with relatively high porosity and permeability,but its heterogeneity is strong ,gas accumulation is driven by both expansion and buoyancy .