Stress orientation, pore pressure and least principal stress in the Norwegian sector of the North Sea

Abstract

We have compiled data on stress orientation, pore pressure and least principal stress from over 300 wells in the Norwegian sector of the North Sea. Well-defined regional variations are observed in all three parameters. Incorporation of precise stress orientation data from drilling-induced tensile borehole wall fractures shows that the orientation of maximum horizontal stress is approximately E–W between 60°N and 62°N but tends to be NNW–SSE south of 58°N, similar to the average stress direction seen throughout Great Britain and continental NW Europe. We believe this rotation is due to the superposition of plate-driving stresses with those associated with lithospheric flexure caused by deglaciation. Regional variations of the magnitude of the least principal stress and pore pressure also appear to support the hypothesis that the stress field in this region has been strongly affected by deglaciation.