Effects of mineral composition on the fracture propagation of tight sandstones in the Zizhou area, east Ordos Basin, China

Abstract

To reveal the effect of mineral composition on fracture propagation of sandstones, a series of experiments were performed on quartz arenite and sublitharenite. Two fracture propagation mechanisms were identified in sandstones: intragranular and intergranular fractures. As determined by the mechanical properties of minerals, grain fracturing occurred in a majority of detrital quartz and a small amount of quartz cement, feldspars and carbonate cement, exhibiting typical brittle behavior and forming intragranular fractures. Due to the residual space between brittle detrital grains, which act as “flaws” in the sandstones that could initiate a stress concentration, the intergranular fractures occurred only between brittle grains. As cement are situated at the contact locations between detrital grains, mechanical properties and the occurrence of cement played an important role in intergranular fracture propagation. No intergranular fractures occurred between detrital quartz cemented by clay or carbonate, while quartz overgrowths did not hinder the propagation of intergranular fractures.