The authors describe an experiment to characterize in detail variations in the state of stress within a horizontally-bedded sandstone/shale limestone sequence in western New York. The measurements were made using a new wireline-based 'microfrac' system which, by its nature, permits frequent sampling of stress. Three wells, 1 km or so apart featured in the study. In one well, 43 intervals were tested to 1 km depth. The measured stress-profiles in all three wells show an identical pattern of stress variations. Two stratigraphic regimes of markedly different stress ratio are recognized which are separated by a transition zone. Within this zone variations in stress are clearly correlated with lithology.
|Published - Dec 1 1986
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