Diagenesis in Mesozoic carbonate rocks in the North Pyrénées (France) from mineralogy and fluid inclusion analysis: Example of Rousse reservoir and caprock

Abstract

Abstract Fluid-rock interaction is of key interest for deciphering the geodynamic history of complex geological environments. In this paper, we describe the mineralogy and petrography of the Rousse reservoir (the Upper Jurassic “Dolomie de Mano” formation) as well as the reconstruction of its thermal and pressure history. We also investigate the base of the reservoir caprock (the Campanian breccia). A satellite of the giant gas field of Lacq in the south-west of France, Rousse was a gas producer until it moves to a CO2 storage site in 2010. Rousse is located within a deep, isolated, faulted, carbonate Jurassic horst overlain by a 4500\u202fm thick overburden that is composed of a series of turbiditic flysch deposits of Upper Cretaceous (Cenomanian) to Tertiary (Eocene) age. Cores were sampled from two wells, Rousse 1 and 2, and were analyzed by ICP-MS, XRD, SEM, EPMA, TEM, cathodoluminescence and fluid inclusion techniques. Pressure-Temperature (P-T) conditions were derived by modeling data from fluid inclusions trapped in the fracture minerals of the “Dolomie de Mano” formation and the Campanian breccia. In the “Dolomie de Mano”, diagenesis was dominated by three dolomite episodes followed by a calcite stage in fractures. The second and third dolomitizations were associated with fracturing episodes. These dolomites precipitated from low-saline (