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Impact of geodynamics on fluid circulation and diagenesis of carbonate reservoirs in a foreland basin: Example of the Upper Lacq reservoir (Aquitaine basin, SW France)

Elias Bahnan, Alexy and Carpentier, Cédric and Pironon, Jacques and Ford, Mary and Ducoux, Maxime and Barré, Guillaume and Mangenot, Xavier and Gaucher, Eric C. (2020) Impact of geodynamics on fluid circulation and diagenesis of carbonate reservoirs in a foreland basin: Example of the Upper Lacq reservoir (Aquitaine basin, SW France). Marine and Petroleum Geology, 111 . pp. 676-694. ISSN 0264-8172. https://resolver.caltech.edu/CaltechAUTHORS:20190903-104540627

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Abstract

Orogeny-driven fluids that circulate in foreland basins can have strong impacts on petroleum systems and reservoir properties. This applies to the Upper Cretaceous Lacq reservoir of the Aquitaine Basin in southwestern France located north of the Pyrenean Mountains. We study a drillcore from a 650 m deep oil reservoir to document how the evolution of a foreland basin, which formed after a hyperextension phase, affected fluid circulation and eventually reservoir diagenesis. Using drillcore samples, petrographic observations, fluid inclusion studies coupled with thermodynamic modeling, isotopic and rare earth element geochemistry, as well as basin modeling were performed to investigate and describe the fluid types and sources, the pressure-temperature evolution and the timing of diagenetic fluid flow. Early diagenesis involves some bacterial activity represented by micrite rims and framboidal pyrites, as well as early dolomitization involving a mixture of meteoric and formation fluids. During burial, dolomite overgrowth, saddle dolomites, coarse blocky calcites and anhydrites precipitate. The last products consist of iron oxide precipitation and meteoric recharge of the reservoir with groundwater. Our results indicate that after the deposition of the Paleocene flysch formation, Mg-rich, low salinity, hot, and relatively deep clay-released fluids migrated along thrust faults from deeper parts of the basin during the climax of the compressional Pyrenean phase (Eocene). They acted as dolomitizing hydrothermal fluids with a thermal disequilibrium in the order of 30–40 °C hotter than the ambient host rocks. Another orogeny-driven, hydrothermal and Mg-poor fluid mixed with oil generated by Jurassic-Barremian source rocks and precipitated calcites and anhydrites. Finally, during uplift, oxidizing fluids were laterally introduced as the present-day groundwater. Hence, by combining different petrographic, geochemical and modeling proxies, we document how the Eocene orogenic phase played a crucial role in basin-scale fluid flow and carbonate diagenesis.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.marpetgeo.2019.08.047DOIArticle
https://data.mendeley.com/datasets/gyckp5hdgp/1Related ItemData
ORCID:
AuthorORCID
Pironon, Jacques0000-0002-0585-3227
Mangenot, Xavier0000-0001-8770-6767
Gaucher, Eric C.0000-0002-7976-8455
Additional Information:© 2019 Elsevier Ltd. Received 23 May 2019, Revised 25 August 2019, Accepted 26 August 2019, Available online 30 August 2019. This work was funded by the Center de Recherches sur la Géologie des Matières Premières Minérales et Energétiques (CREGU), contract number FR00008500-FR00009038, and TOTAL EP-R&D. Sylvain Calassou and the colleagues from the Center Scientifique et Technique Jean Féger de TOTAL (CSTJF-TOTAL) are warmly thanked for providing access to their facilities and data archives to conduct this research. The authors are grateful to the constructive comments and revisions of Enrique Gomez-Rivas and an anonymous reviewer that have greatly improved the quality of the manuscript. Olivier Fonta from GEOPETROL is thanked for giving access and permission to acquire core samples. Laurine Duvivier is acknowledged for her input on the basin modeling. Pierre Cartigny from the Institut de Physique du Globe de Paris (IPGP) is kindly acknowledged for his assistance with the multiple sulfur isotopes analysis. John Eiler and Nami E. Kitchen from California Institute of Technology (Caltech), United States are warmly thanked for their help and support with the clumped isotope analysis.
Funders:
Funding AgencyGrant Number
Center de Recherches sur la Géologie des Matières Premières Minérales et Energétiques (CREGU)FR00008500-FR00009038
Total EP-R&DUNSPECIFIED
Record Number:CaltechAUTHORS:20190903-104540627
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20190903-104540627
Official Citation:Alexy Elias Bahnan, Cédric Carpentier, Jacques Pironon, Mary Ford, Maxime Ducoux, Guillaume Barré, Xavier Mangenot, Eric C. Gaucher, Impact of geodynamics on fluid circulation and diagenesis of carbonate reservoirs in a foreland basin: Example of the Upper Lacq reservoir (Aquitaine basin, SW France), Marine and Petroleum Geology, Volume 111, 2020, Pages 676-694, ISSN 0264-8172, https://doi.org/10.1016/j.marpetgeo.2019.08.047. (http://www.sciencedirect.com/science/article/pii/S0264817219304192)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:98385
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:03 Sep 2019 18:01
Last Modified:03 Oct 2019 21:40

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