Natural Fractures -Limestone VS Dolomite: Comparing Fracture Characteristics in the Canyon (Sacroc Field, TX) and the Arbuckle (Wellington Field, KS) Formations.

John Lorenz, Scott Cooper, Renee Robertson, and Lynn Watney
FractureStudies LLC, Edgewood, NM, Kinder Morgan, Kansas Geological Society

Natural fractures are common in carbonates, even in relatively unstructured, flat-lying strata. In equivalent structural settings, however, fractures in dolomite are typically better developed and have more variety than fractures in limestone. Studies of cores from the Arbuckle dolomites in the Wellington field of southern Kansas, and from the Canyon limestones in the Sacroc field of West Texas, show that multiple sets of extension fractures with intersecting strikes are common in both settings, but that fractures are typically taller and more irregular in dolomites. Stylolites and clay partings arrest vertical fracture propagation in both settings, thus fractures are short in lithologies that contain numerous such heterogeneities, but they are more closely spaced in the dolomites. Dissolution along fractures was an important process in both lithologies, but it has been better developed in the Arbuckle dolomites where fracture-controlled dissolution produced irregular vertical slots up to five ft tall and nearly a centimeter wide. Dissolution also opened irregular slots along horizontal planes; the slots are narrow and follow stylolites in the limestone; they are wider and more irregular in the dolomites where their parentage, possibly bed-parallel shear, is less obvious.

AAPG Search and Discovery Article #90152©2012 AAPG Southwest Section Meeting, Fort Worth, Texas, 19-22 May 2012