Our Ambition

Our ambition in the fluids project has been to integrate the full story of the basin related fluids. For this purpose, 13 research operations have been launched since 2016.

Our playground is the Aquitaine Basin and the Pyrénées Foothills. We are trying to integrate strongly the sub-project “Fluids” to the “Orogen” sub-project. Orogen give the structural architecture and the geodynamic evolution of the zone where our fluids are reacting and are flowing.

Starting with the Lacq reservoirs a first action ((1) PhD Alexy Elias-Bahnan) is dedicated to the diagenesis of the deep Lacq and Upper Lacq rocks. Combined to this thesis, the post-doc of Guillaume Barré (2) aims at understanding the origin of gas in the reservoirs and in particular the origin of H₂S. In parallel, a mapping of the gases exhaled at the surface, mainly along the major structural accidents, is performed by a PhD (Nicolas Lefeuvre (3))  Outcrops of the reservoirs rocks are accessible in the “Chainons Béarnais”, the PhD of Geoffrey Motte (4) will allow to understand the dolomitization processes in several tectono-sedimentary contexts.

Exceptional Syn-Rift mineralization (Talc, Dolomite) has also been studied in order to record the chemical and P/T conditions of this critical event (Post-doc of Benoit Quesnel (5).

During the burial of the sediments and the collision, fresh waters are expulsed from clay formations. The PhD of Jessica Strydom (6) experiments this water productions by mechanical experiments coupled to various thermal conditions. And one action with the French Geological survey (BRGM Joachim Trémosa/ Hélène Gailhanou) aims at to model numerically the water production during compaction and dehydration of clays (7).

The H₂S production by Thermal Sulfate Reduction studied by Guillaume Barré can have a major consequence on the karstification due to the oxidation of this gas into sulfuric acid. Dimitri Laurent is studying this process during his post-doc (8).

The relatively high temperature of the hydrothermal springs manifests generally the contribution of deep fluids. The BRGM is in charge to characterize this type of waters in a collaboration leaded by Joachim Tremosa and Frédéric Gal (9). In our findings during this project, the presence of abiotic gases (CH₄, H₂) in some wells, close to the North Pyrenean Frontal Thrust (NPFT), was a surprise.

The production of hydrogen by serpentinization is not so well documented and the PhD of Camille Tichadou (10) is studying this process with pure Olivine and Pyrenean Ultrabasic Rocks. Camille Tichadou is also studying the petrology of these Ultrabasic Rocks. The serpentinization reaction is also catalyzed by the presence of some metals. Samuel Barbier (PhD) is studying these reactions (11).

The crystallization of serpentine minerals increases strongly the volume of the rocks and is supposed to increase strongly the hydraulic pressure contributing to the fracking of the rock and to the expulsion of the gases and brines. The PhD of Bruno Leclère experiments the crystallization pressure question (12).

Finally, with Dimitrios Rallakis (Post-Doc, 13), we are revisiting the hydrocarbons production in the Mauléon-Arzarcq basin integrating the thermicity history and the geological structure detailed in “Orogen” and our new understanding of the TSR.