Hydrofrac Stress Measurements under Conditions of High Temperature

Abstract

The effect of thermal stress on the so-called shut-in pressure is investigated theoretically and experimentally for in-situ stress It is considered here that a pre-existing high temperature around a borehole is disturbed due to circulation of cold water before a packer system is set at a depth in borehole. The results show that a value of the in-situ coinpressive stress normal to the crack plane can be estimated from variation of the shut-in pressure with the period of circulating time as follows. At first, the shut-in pressure is plotted as a function of the period of circulating time to the power of 0.68. The line is extrapolated to the time when the period of circulating time is zero. Then, a value of pressure determined by the extrapolation gives the value of the in-situ compressive stress normal to the crack plane.