Recognition and use of induced fractures and other features in core produced by the coring process

摘要

There are several distinctive types of coring-induced fractures that can be recognized in core on the basis of morphology, assisted by certain characteristics such as edge effects and surface ornamentation. The shape and orientation of many of these induced fractures offer information on the in-situ stress conditions and the coring process. Petal, petal-centerline, scribe-knife, disc, and torque-related fractures may all be caused by coring in vertical wells. Saddle fractures, (related to petal fractures) are unique to horizontal core, as is the polishing of fracture surfaces during coring. Other features such as scribe-line rotation, hammer marks, and rotary-bit patterns are important in making correct interpretations of the in situ stress and reservoir permeability, and in making the maximum use of the evidence bearing on reservoir fracture-system permeability provided by both induced and natural fractures.