鄂尔多斯盆地定北上古生界致密砂岩储层脆性特征及影响机理OA

The brittleness of the Upper Paleozoic tight sandstone reservoirs in the Dingbei area and the corresponding impact factors are of great practical significance when selecting the"sweet spot"between project development and exploration risk assessment.Based on X-ray diffraction measurements,scanning electron microscopy,rock mechanics experiments,and core thin section and physical data,the mineral components and mechanical brittleness characteristics of the tight sandstone reservoirs in the study area were analysed and evaluated,with the aim of identifying the main controlling factors of the brittleness and its influencing mechanism(s).This study shows that the brittleness of tight sandstone reservoirs in the Upper Paleozoic Tai-2 member of the Shanxi Formation and the He-1 member in the Dingbei area is mainly affected by the mineral components and structure of the rocks.Among them,the quartz and clay mineral contents have the largest influence on the brittleness of the rocks.When the contents of these mineral components are similar,the particle-supported structure formed by coarse-grained sandstone has a relatively high brittleness,and the mechanical properties of the mineral structure are mainly affected by modification via diagenetic action.In the study area,the tight sandstone reservoirs of the Tai-2 section as a whole show the lithogenic evolution mode of"strong compaction-strong dissolution-strong cementation,"where the mineral structure is closely connected,and the brittleness is relatively good.The distribution of brittleness is mainly affected by the depositional environment,whereby the coarse-grained sandstone is more developed and has higher quartz content in diversion channels resulting from stronger hydrodynamic conditions,implying they are high-quality mechanically brittle reservoirs.These research results have important reference significance for deepening our understanding of brittleness of tight sandstone reservoirs and evaluating"sweet spot"from engineering perspective.