This paper introduces one method to detect the fractures induced during the hydraulic fracturing in-situ stress measurement process. This method can detect the hydraulic fracture fairly well, and can define the strike of induced fractures exactly so as to determine the orientation of the maximum horizontal principal stress. After the measured data were compared with the results gained with the traditional fracture impression method, the findings show that this method is of high precision and operation speed, simple and energy and time-saving. Especially in the deep measurement boreholes and boreholes with thick mud coat on the all, this new method has much superiority over the traditional method, which offers a new means to determine the direction of the maximum horizontal principal stress. Therefore, this new method is of great application value in the engineering practice and rock mechanics research.
Originally, the hydraulic fracturing technology is one method to improve the oil recovery in the oil industry. Large amounts of logging data indicated that the direction of hydraulically induced fractures coincided with the orientation of the maximum horizontal principal stress of a regional stress regime. After that many scientific researchers had done lots of research on how to utilize the hydro fracturing technology to determine the in-situ stress, and almost all the research findings have proven the reliability of the hydro fracturing in-situ stress measurement method. Since 1970s, this method was widely applied in the geological and geotechnical area. The ISRM specified this method as one of the recommended methods to determine the in-situ stress (ISRM 1987). The hydro fracturing in-situ stress measurement method can not only determine the magnitude of stress, but also can define the orientation of the maximum horizontal principal stress through detecting the strike of induced fracture (Haimson & Lee 2003).