Using shear waves to predict lateral variability in vertical fracture intensity

During the last five years, the use of shear‐wave splitting in geophysical exploration has made the transition from research project to very promising field technique. The measurement of the azimuth of the fast shear‐wave and analysis of the S-wave splitting (or birefringence) are now commonplace. Furthermore, a very timely practical application is suggested by the recent proposal that reflectivity on post‐rotation S1 and S2 data sets should indicate lateral variation of anisotropy. This could be of great value because the determination of lateral variation in fracture intensity in a vertically fractured sedimentary layer is necessary to insure high efficiency in a horizontal drilling program designed to drain the fractures.