Description and Interpretation of Natural Fracture Patterns in Sandstones of the Frontier Formation Along the Hogsback, Southwestern Wyoming. Topical Report, June 1991-January 1994

摘要

Three categories of natural fractures are present in Frontier Formation sandstones along the Hogsback, a thrust-plate ridge in southwestern Wyoming. J1 fractures formed during basin subsidence prior to thrusting, and strike north-south parallel to the basin axis. J2 fractures formed as a result of north-south dilatency during early thrusting, and trend generally normal to the ridge. Tear faults and lateral ramps within the thrust plate produced localized J3 fractures with strikes that vary between locations. Diagenetic sequences in the Frontier Formation sandstones also controlled the development of fracture sets. At one outcrop, J1 fractures occur in sandstones that were cemented early with quartz, J2 fractures occur in sandstones that were not cemented early but that contain later calcite cement, and both fracture sets are present in sandstones that contain both cements.