f Moveable Fluid Saturation Of Tight Sandstone And Its Formation Mechanism: A Case Study Of Zhenbei Oil Field In Ordos Basin

Tight sandstone makes pore structure extremely complex and one of its effects is the commonly lowness of movable fluid saturation which directly controls economic profits. Because of highly burial depth around 2100m, the reservoir has experienced strongly digenesis. The primary intergranular porosity lost by compaction and silicon cementation is great. Later dissolution of debris is conducive to secondary pore formation and dissolved pore cemented by clay minerals can turn out to be crystalline pore, the quality of which is worse than that of dissolved pore. The throat-body volume is usually roughly the same as the pore-body volume. With the common sense of radius of throat smaller than that of pore, it is easy to understand the number of throats bigger than that of pores. The average movable fluid saturation is less than 50%. Compaction and silicon cementation are basic causes of tight sandstone. Dissolution is the mainly constitute of movable fluid saturation and crystalline pore ‘contribution to movable fluid saturation is poor. The pore-body volume accounts for main part of movable fluid saturation and the contribution of throat-body volume to movable fluid saturation depends on the distribution of throat radius. Large throat has bigger contributive potential than small one. Factors of movable fluid saturation have been then divided into two groups: The former includes dissolved pore content and pore-body volume while crystalline pore content and throat-body volume consist of the inferior one.