A new strategy of hydrofracturing for deep stress measurements,BABHY, and its application to a field test

For the effective measurement of the reopening pressure in hydraulic fracturing, it is necessary to use the testing equipment with sufficiently small compliance. This limitation makes it difficult to apply the hydraulic fracturing for the measurement of the maximum stress, because the compliance of conventional equipments is generally so large. Taking account of this situation, we have proposed recently a new method which will allow us to measure both of the maximum and minimum stresses by in-situ tests of hydraulic fracturing at a depth greater than a few km. We call the method the Baby Borehole Hydrofracturing or BABHY for short. In order to put the new method into practice, we developed the BABHY sonde and finallywe succeeded in applying it to an in-situ test at a depth of 811 m in a vertical borehole drilled from the ground surface