Altobi, Younis K.1, RK Goldhammer1, Daniel J. Lehrmann2
(1) The Unviersity of Texas at Austin, Austin, TX
(2) University of Wisconsin-Oshkosh, Oshkosh, WI
ABSTRACT: Sequence Stratigraphic Controls on Dolomitization, Structural Deformation and Fracture Distribution in Carbonate Strata, the Cupido Formation, Sierra Madre Oriental, Northeast Mexico
The degree of dolomitization is a significant influence on fracture development and
distribution within carbonate strata. The Cupido Formation (700-1200 m thick) of NE Mexico
is a Barremian to Aptian low-angle carbonate bank that rimmed parts of the ancestral Gulf
of Mexico and is equivalent to the Sligo Formation of the Texas Gulf section. It consists
of shallow water carbonates and was deposited during the second order HST of the 120 my
supersequence and the early TST deposits of the Albian supersequence.
A study of dolomite abundance within a sequence stratigraphic framework in the Cupido
carbonates indicates pervasive dolomitization within late highstand (HST) and early
transgressive (TST) system tracts of third order depositional sequences. Dolomitized beds
are not lithofacies specific, and in most cases they represent the caps of the
shallowing-upwards cycles. Early extensional deformation (fractures cut by bed-bounding
burial stylolites and growth faults) formed due to the movement of Jurassic-aged salt are
common within the Cupido. Early fractures are more common in dolomitized facies than in
limestone. Measured stratigraphic sections, fracture intensity measurements through
scan-lines and field observations, and petrographic and statistical laboratory analysis of
dolomite and fracture distribution within the interpreted stratigraphic framework are
being used to develop a model that quantifies stratigraphic controls on dolomitization and
fracturing.
Previous fracture studies were focused on the relationship between fracture density and
rocks mechanical properties (i.e. lithology and bed thickness). However, improved
prediction in subsurface reservoir studies can be accomplished by quantifying fracture
distribution within a predictable sequence stratigraphic framework.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004