The borehole method of rock massive stress state estimation

In permeable rock the hydraulic fracturing stress measurement is carried out using such impenetrable shell as a packer and a sleeve that prevents from fluid injection into the fracture and rock. The stress states are determined from several fracture reopening pressures on condition that cracks have different orientation in reference to a maximum stress. Numerical modeling of this problem shows the gradual character of the crack opening in the borehole and the influence of an indefinable initial crack length on the reopening pressure value Pr of other fractures. As a solution the using of a singular radial fracture and the measuring of fracture opening value on the outline dependence of the pressure in the impenetrable shell are proposed. The fractures are induced by hydraulic fracturing in advance. The test of the solution is carried out using singular integral equations of linear fracture mechanics. The fracture opening pressure and fracture opening value on the outline dependence of the fracture opening portion length and external stress field is determined. The principal stress ratio estimation algorithm is developed. The ratio of principal stresses is an additional parameter and it is used to find out the stress with the fracture reopening pressure on the borehole wall.