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Fractures and Stress |
Department of Earth Sciences, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
This paper reviews the benefits and limitations of the use of four-arm dipmeter logs to detect breakouts, and to estimate horizontal stress trajectories. An example is given from southwestern Ontario, a low seismic risk area, yet one with unusually high horizontal stresses, causing contemporaneous deformations such as pop-ups and tunnel closures. The preliminary results show that the relatively few breakouts detected follow two main trends, approximately N80°E and S80°E. The breakouts often have different orientations within the same well, but do not seem to ‘prefer’ a particular lithology. The data, when compared to other stress measurements, do show a general NE trend for compressive stress, as popularly believed. However, they are as yet too few to make statistically reliable assumptions on the stress state in the area.
