The diagenetic history of the giant Lacq gas field, witness to the apto-albian rifting and the Pyrenean orogeny, revealed by fluid and basin modeling

The link between fluid circulation schemes and basin histories remain one of the most valuable tools to understand diagenetic evolution petroleum reservoirs. This study proposes a model for Deep Lacq reservoir constrained by petrography, geochemistry, inclusions studies modeling analyses. Drill cores penetrating 3000 m deep Late Jurassic Early Cretaceous “Deep Lacq” reservoirs, in Aquitaine SW France, were used investigate how geodynamic influenced diagenesis experienced phase rifting during Lower followed inversion compression Paleogene. Petrographic geochemical results indicate that early involved bacterial activity dolomitization. Fluid thermodynamic modeling, coupled with reconstruction history provided insight into timing circulations. Burial rift-related dolomitization episode linked mainly recrystallization earlier dolomites hot fluids connected Triassic evaporites. dolomitizing circulated at temperatures close 136–144 °C pressures 338–386 bars, Aptian (120-116 Ma). During post-rift uplift its subsequent thermal re-equilibration, multiple pulses precipitated coarse blocky calcites. These Ca-rich 109 97 Ma, high-pressure conditions around 704–766 bars 146–156 °C. another pulse resulted precipitation anhydrite cements is onset Pyrenean orogeny. No evidence support in-situ TSR reactions found, which suggests migration TSR-related H2S from kitchen deeper parts basin. multi-modeling approach shows detailed analyses can add constraints on eventually it larger-scale basin's history.