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http://dx.doi.org/10.7474/TUS.2011.21.2.128

Numerical Approach for Determination of Shut-in Pressure in Hydrofracturing Test  

Choi, Sung-O. (강원대학교 공과대학 에너지.자원공학과)
Publication Information
Tunnel and Underground Space / v.21, no.2, 2011 , pp. 128-137 More about this Journal
Abstract
The shut-in pressure calculated in common hydrofracturing test for vertical borehole equals generally to the minimum horizontal principal stress, so it should be considered as an essential parameter for determining the in-situ stress regime around the rock mass. It shows usually an ambiguous value in pressure-time history curves, however, because of the relationship between the behavior of hydraulic fractures and the condition of remote stress regime. In this study, a series of numerical analyses have been carried out to compare several methods for determining the shut-in pressure during hydrofracturing. The hydraulic-mechanical coupling has been applied to numerical analysis for simulating the fracture propagation by hydraulic pressure, and the different discontinuity geometry has been considered in numerical models to examine the effect of numerical element shape on fracture propagation pattern. From the numerical simulations with the four different discontinuity geometries, it was revealed that the shut-in pressure obtained from graphical methods rather than statistical method was relatively small. Consequently a care should be taken in selecting a method for determining the shut-in pressure when a stress anomaly around borehole and a fracture propagation with complicate mechanism are considered.
Keywords
Shut-in pressure; Hydrofracturing; Numerical analysis;
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