Analysis of Crack Formation in Model Specimens During Hydraulic Fracturing in Holes

Abstract

This study relates to the technological aspect of hydraulic fracturing stress measurement technique widely applied currently for stress assessment in rock. The physical simulation data on hydraulic fracturing of the wall of a borehole are presented. The experiments were carried out in polymethacrylate cubes with edge length of 200 mm. In the specimens, either open-end or blind holes were drilled with a diameter of 12 mm at the center of one of the cube faces. In some specimens, longitudinal and transverse slots were cut to promote stress increase under critical pressure of hydraulic fracturing. The hydraulic fracturing tests were implemented using a prototype borehole survey tool designed to seal the assigned interval in the hole and feed it with fluid (glycerin) under pressure. The behavior of hydraulic fractures was studied at 12 model specimens. The experimental results are compiled in the table and contain some canonical information on the nature and features of initiation of hydraulic fractures in the vicinity of measurement holes under different stress conditions of the host medium. The physical simulation results can be used in formulation and solution of analytical problems in hydraulic fracturing stress measurement, or to advance in the technology of in situ directional hydraulic fracturing and stress measurement in underground mines.