Stress Measurements - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 529

Figure 16.16 Example of a hydraulic fracturing test, pressure versus time and flow rate versus
time plots and stress calculation
Various methods are in use to identify p s , which require high resolution of pressure
versus time records and subsequent analyses (Aamodt & Kuriyagawa 1983, Doe et al.
1983, Enever & Chopra 1986, Lee & Haimson 1989, Hayashi & Haimson 1991, Cornet
1993, Rutqvist & Stephansson 1996). The large number of approaches is a hint as to
some uncertainties which remain with regard to the identification of p s as is the case
for the hydraulic pressure versus time plot represented in Fig. 16.16. The detection of
shut-in pressure in the frac cycle in this case was indistinct and thus could not clearly be
identified so that no p s value was specified.