Data quality of in-situ stresses by hydraulic fracturing method; Applicability of high-compliance system and evaluation of maximum stress based on the results in granite

Sato, Toshinori  ; Tanno, Takeo; Hikima, Ryoichi; Sanada, Hiroyuki; Kato, Harumi*

Hydraulic fracturing has provided many determinations of in situ stress, but also include many errors in data obtained, as the ISRM suggested. This report provides a comparison of the data obtained by the conventional hydraulic fracturing method with those of a new high-compliance system. Analysis of the results of 57 hydraulic fracturing tests in granite to a maximum depth of 1000m, indicated that 35% of the data obtained using the conventional system is low quality. In addition, the maximum horizontal stresses calculated using the conventional equation is overestimated by about 23%. In contrast, the data obtained with the new system is better quality compared with the conventional system, because flow rate of pressurization is measured in the borehole near the test section rather than at surface, thus reducing compliance in the system and the inherent errors introduced in the stress calculations.