Fracture Azimuth—A Shallow Experiment

A small-scale, shallow experiment was conducted by Amoco Production Research, Sandia Laboratories, and the U. S. Geological Survey, in order to study the potential of several geophysical monitoring techniques for determining in-situ fracture geometry. The program included core analysis, surface strain gage over-coring, borehole measurements, tiltmeter surveys, surface electric potential measurements, and post-coring. Each of the techniques correctly measured an East-West fracture which was longer to the East. This azimuth was apparently controlled by in-situ stresses, and it was noted that these were not affected by a horizontal stress relief located due East of the site.