Analysis of crack reopening behavior for hydrofrac stress measurement

Abstract The relation among the so-called reopening pressure, in situ stresses and injection flow rate was clarified theoretically and experimentally for the case that a transverse crack is induced perpendicularly to a borehole axis in hydraulic fracturing stress measurements. The results are summarized as follows. The reopening pressure, i.e. the borehole pressure at which the borehole pressure — time history during pressurization clearly deviates from a linear relationship, is basically governed by the in situ compressive stress normal to the crack plane, Sv. Its magnitude decreases and approaches the magnitude of Sv with decreasing injection flow rate.