Orientation of crustal stresses in the North Sea and Barents Sea inferred from borehole breakouts

The orientations of the greatest horizontal principal stresses (S-H) derived from borehole breakouts are presented for 30 boreholes located in the Central Graben, the Viking Graben, the More-Voring region, and the Barents Sea area. Additional borehole breakout data from 20 other wells for which information about breakout length was available have been used to calculate the mean azimuth of S-H for the four areas of investigation. The mean azimuth of S-H is calculated from the length-weighted distribution of the breakout orientations. In the Viking Graben and the Central Graben a S-H orientation of about N 78 degrees and N 97 degrees was found, respectively. For the More-Voring region a mean S-H orientation of N 127 degrees has been evaluated. Borehole breakout data from the Barents Sea area indicate a S-H orientation of about N 177 degrees. The S-H orientations presented in this study are consistent with the results from previous studies which suggests that the direction of the maximum compressive horizontal stress S-H differs off the coast of Norway markedly from the well documented NW-SE trend of S-H in Western Europe. The observed S-H orientation changes significantly across the investigated regions which may have to be attributed to their complicated geomechanical setting.