The reopening behavior of a transverse crack which is induced on the surface of a borehole by hydraulic fracturing is analyzed to establish the methodology for hydraulic fracturing tectonic stress measurements, where, as a typical transverse crack, a penny-shaped crack which is induced perpendicularly to the borehole axis is considered. To this end, a model is constructed for analyzing the coupled problem of fluid flow in the crack and crack reopening behavior in an impermeable rock. The model takes into account the fact that the crack does not reclose perfectly upon deflation due to crack surface damage and minor shear displacement. The results show that the apparent reopening pressure, i.e., borehole pressure at which the pressure-time history clearly deviates from linearity, decreases and approaches the compressive tectonic stress normal to the crack plane with decreasing injection flow rate, and that it is almost proportional to the compressive tectonic stress independently of injection flow rate.
|Number of pages
|Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A
|Published - 1993 May