Characterisation of Potential Lacustrine Carbonate Reservoirs: The Microbial/Algal Buildups and Associated Carbonate Deposits from the Eocene Green River Formation
Seard, Claire 1; Camoin, Gilbert 1; Rouchy,
Jean-Marie 2; Virgone, Aurélien 3; Pabian-Goyheneche,
Cecile 3; Poli, Emmanuelle 3
(1)Geosciences,
CEREGE-CNRS, Aix en Provence, France. (2) Muséum National d'Histoire Naturelle,
CNRS, Paris, France. (3) GSR/TG/ISS/CARB, TOTAL, Pau, France.
The lacustrine Green River Formation of Wyoming, Colorado and Utah
(USA) was deposited in a series of continental basins (the so-called “Gosiute
and Uinta lakes”) during the Eocene (53.5 to 48.5 Ma). In contrast to the thick
oil shale open facies which were extensively documented in the literature, the
carbonate margins of those systems have received little attention.
Marginal carbonate units extend over more than tens of kilometers
in length and a few kilometers in width and represent potential carbonate
reservoirs with porosities ranging from 5 to 30%. They are usually composed of
large carbonate bodies (up to 10 m-thick) resulting from the piling up of
microbial/algal buildups exhibiting various morphologies (domes, lenses,
pinacles, columns etc.) and internal structures (e.g. tufas, stromatolites,
thrombolites) associated with other carbonate facies, mostly ostracod and ooid
grainstone-packstone, oncoid floatstone and bivalve/gastropod coquinas.
Non-carbonate lithologies, including shales, sandstone and organic-rich facies
(“paper shales” and “oil shales”) are interlayered with carbonate deposits.
The objectives of our field-based study and related subsurface analysis are: 1) to reconstruct the architecture of the carbonate margin and its evolution through time, 2) to reconstruct the depositional model of the lacustrine systems, and 3) to characterize the reservoir properties of the carbonate facies based on CT-scan analysis and petrophysical measurements.
AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.