Article

The determination of in-situ stress from wellbore breakouts in the main borehole of the Chinese Continental Scientific Drilling

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Abstract

The breakouts began to occur under the depth of 1200m in the main borehole of Chinese Continental Scientific Drilling (CCSD), 82 breakout images are collected from acoustic borehole televiewer data between 1200m and 2010m. The averaged orientation of breakouts is 324.8° ± 3.3°. The averaged orientation of maximum horizontal stress is 54.8° ± 3.3°. Using parameters measured from breakouts (depth and width of breakout) and rock cohesive strength determined from triaxial rock compression and deformation test, the magnitudes of principal stress are calculated at 16 different depths of 1269m, 1500m, 2000m and so on. Overburden stress is calculated using the density logging data. According to the orientations and magnitudes of three principal stresses, the least principal stress is horizontal, and stress state (SH > Sv > Sh) determined from the analysis of wellbore breakouts of CCSD indicates the strike-slip stress regime and is coincident with the strike-slip stress field observed from earthquake focal plane mechanisms.

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... Most studies of stress value in the past limited in shallow crust, used stress measurement to obtain the value [1][2][3][4][5][6][7]. But the earthquake was occurred in the tens of kilometers in the crust, detecting the crustal stress level has great significance. ...
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