T. J. Taylor
Amoco Production Company, Tulsa, Oklahoma
Abstract
Most of the fractures associated with faults are shear fractures parallel to the fault, shear fractures conjugate to the fault, or extension fractures bisecting the acute angle between these two shear directions. These three orientations correspond to the three potential fracture directions observed during laboratory fracture experiments and develop relative to the local state of stress causing the fault. The fault is the larger feature of the stress field which caused all of the fractures. By analyzing the fracture patterns on a borehole televiewer log, it is possible to identify a fault-related system of fractures, the fault, and the direction of the principle stresses causing the fault.
Two examples are presented, one is a sand-shale sequence from the Gulf of Suez and the other is from a chalk formation in North Louisiana.