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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