Sample dilation and fracture in response to high pore fluid pressure and strain rate in quartz‐rich sandstone and siltstone

摘要: [1] Natural hydraulic fractures (NHFs) are inferred to form where pore pressure exceeds the least compressive stress by an amount equal tensile strength of rock. We improved upon experimental protocol that meets NHF criterion within cylindrical samples with most effective parallel sample axis. The stresses achieved during these experiments ranged from 17–47 MPa. fluids used had higher viscosities than water and axial strain rate was rapid (∼10−3s−1) delay dissipation fluid flow. Four on St. Peter Sandstone two Abo Formation siltstone were performed under conditions drained conditions. None resulted in failure, but all sandstone one fractured response elevated pressures. Consistent field theoretical studies, mechanical heterogeneity a first order control fracture location. In absence mesoscopic heterogeneity, location coincided maximum pressure. Samples responded pressures differential dilating, magnitude which sufficient achieve atmospheric failed 2 250 s after experiencing greatest pressures, when no longer tensile. Thus, high experienced early rocks, even though they not sustained until failure. These results provide insight into processes fluid-driven formation.