Petrophysical assessment of a carbonate-rich caprock for CO2 geological storage purposes

International audienceWe present an experimental study of the retention/flow properties of the caprock of the Rousse depleted gas field, where up to 120000 tons of CO 2 are to be injected over a 2-year period. One of the caprock samples examined comes from the carbonated breccias overlying the reservoir, a deep Jurassic horst, whereas the other samples come from the 2000 m-thick Upper Cretaceous marl (carbonated turbidites) located above these breccias and the reservoir. The single-phase (brine) intrinsic permeabilities of the marly samples turn out to be extremely low and stress-sensitive. They vary from 20-25 nanoDarcy for the most permeable sample at low stress, to below 1 nanoDarcy at effective stresses in the range of 10 MPa and above. These latter values are lower by at least one order of magnitude than the published values for the caprocks of the Weyburn field and Utsira aquifer. However, the permeability of the brecciated sample is considerably higher, and decreases from ca. 0.1 to 0.003 milliDarcy when the effective stress increases to 20 MPa, which possibly reflects some of the reservoir petrophysical behavior. Gas breakthrough (BT) experiments are undertaken on two of the marly samples fully saturated with brine, using either CO2 or nitrogen as the gas phase. One sample is able to resist CO2 excess pressures as large as 7.6 MPa, whereas in the other more permeable sample a relative pressure of 4.5-6 MPa is enough to induce the BT of nitrogen, a gas with interfacial properties more favourable than CO2 to capillary sealing. Nitrogen flow following BT is extremely limited, with an effective permeability below 1 nanoDarcy. Upon subsequent sample resaturation with brine and then BT with CO2, some alteration of the sealing behaviour is observed, manifested by a decreased BT pressure and an increased gas effective permeability

Investigation of shock/elastic obstacles interactions by means of a coupling technique

International audienceArrays of obstacles have proved to be an efficient way of attenuating shock waves generated by large scale explosions. The present study intends to take into account fluid-structure interactions that may occur when elastic obstacles are used. A tractable coupling tool based on a partitioned procedure is exposed, validated on the supersonic flutter of a panel and applied to a configuration composed of square section cylinders. Several numerical difficulties related to staggering are emphasized and workarounds discussed. A methodical procedure involving one and two-way coupled simulations highlights the influence of material properties as well as the acceleration of waves in the fluid when an initial motion is prescribed to the obstacles. Finally, it is shown that uncoupled simulations may be relevant to investigate shock mitigation in some given cases

Wettability Alteration of caprock minerals by acid gases

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CO2 Injectivity in Geological Storages: an Overview of Program and Results of the GeoCarbone-Injectivity Project Injectivité du CO2 dans les stockages géologiques : programme et principaux résultats du projet ANR GéoCarbone-Injectivité

The objective of the GeoCarbone-Injectivity project was to develop a methodology to study the complex phenomena involved in the near wellbore region during CO2 injection. This paper presents an overview of the program and results of the project, and some further necessary developments. The proposed methodology is based on experiments and simulations at the core scale, in order to understand (physical modelling and definition of constitutive laws) and quantify (calibration of simulation tools) the mechanisms involved in injectivity variations: fluid/rock interactions, transport mechanisms, geomechanical effects. These mechanisms and the associated parameters have then to be integrated in the models at the wellbore scale. The methodology has been applied for the study of a potential injection of CO2 in the Dogger geological formation of the Paris Basin, in collaboration with the other ANR GeoCarbone projects. L’objectif du projet GéoCarbone-Injectivité était de définir une méthodologie pour étudier les phénomènes complexes intervenant aux abords des puits lors de l’injection de CO2. La méthodologie proposée s’appuie sur des expérimentations interprétées numériquement à l’échelle de la carotte afin de comprendre (modélisation physique et lois de comportement) et de quantifier (paramétrisation des outils de simulation) les différents mécanismes susceptibles de modifier l’injectivité : les interactions roche/fluide, les mécanismes de transport aux abords du puits d’injection et les effets géomécaniques. Ces mécanismes et les paramètres associés devront ensuite être intégrés dans une modélisation à l’échelle métrique à décamétrique des abords du puits d’injection. Cette approche a été appliquée pour l’étude d’une injection potentielle de CO2 dans la formation géologique du Dogger du Bassin Parisien, en relation avec les projets ANR GéoCarbone

A Geochemical Approach for Monitoring a CO 2

This paper presents the geochemical characterization of various gas end-members involved in a depleted gas field CO2 storage pilot (Rousse, France). In this pilot, CO2 is produced by oxycombustion from natural gas transformed into fuel gas at the Lacq plant, and transported in a pipeline 30 km away to the depleted gas reservoir of Rousse. Gases produced at Rousse before CO2 injection, the Lacq fuel gas and the CO2 resulting from the oxy-fuel combustion were sampled, together with gases from a –45 m monitoring well and from soils in the vicinity of the Rousse structure. For all samples, the bulk gas composition, the carbon isotopic compositions and the abundance and isotopic signatures of the noble gases were determined. The bulk gas compositions of the Rousse natural gas are comparable to the Lacq fuel gas with methane as the main compound with residual C2-C5 and CO2. Soil gases are typical mixtures of air with biogenic CO2 (up to 9-10%), while the monitoring well gases display typical air compositions with no excess CO2 The Rousse gas and the Lacq fuel gas have δ13CCH4 values of –41.0‰ and –43.0‰ respectively. The injected CO2 out of the oxycombustion chamber has a δ13CCO2 of –40.0‰, whereas δ13CCO2 value for soils samples is comprised between –15 and –25‰. The Rousse natural gas and the Lacq fuel gas are both characterized by a high He enrichment, and depletion in Ne, Ar and Kr compared to the air values. The oxyfuel combustion process provides a CO2 with the He enrichment of the Lacq fuel gas, and a Ne, Ar and Kr composition reflecting that of the oxygen produced at the Air Separation Unit (ASU). Indeed, Ne is depleted relatively to the air, while Kr is enriched up to tenfold, which results from the cryogenic separation of the air noble gases within the ASU. Soil samples noble gas compositions are equivalent to that of the air. In the light of these results, the compositions of the various end-members involved in this CO2 storage pilot suggest that noble gas compositions produced by oxyfuel process are sufficiently exotic compared to compositions found in nature (reservoir, aquifer and air) to be directly used as tracers of the injected CO2, and to detect and quantify leaks at soil and aquifer levels

A Geochemical Approach for Monitoring a CO

This paper presents the geochemical characterization of various gas end-members involved in a depleted gas field CO2 storage pilot (Rousse, France). In this pilot, CO2 is produced by oxycombustion from natural gas transformed into fuel gas at the Lacq plant, and transported in a pipeline 30 km away to the depleted gas reservoir of Rousse. Gases produced at Rousse before CO2 injection, the Lacq fuel gas and the CO2 resulting from the oxy-fuel combustion were sampled, together with gases from a –45 m monitoring well and from soils in the vicinity of the Rousse structure. For all samples, the bulk gas composition, the carbon isotopic compositions and the abundance and isotopic signatures of the noble gases were determined. The bulk gas compositions of the Rousse natural gas are comparable to the Lacq fuel gas with methane as the main compound with residual C2-C5 and CO2. Soil gases are typical mixtures of air with biogenic CO2 (up to 9-10%), while the monitoring well gases display typical air compositions with no excess CO2 The Rousse gas and the Lacq fuel gas have δ13CCH4 values of –41.0‰ and –43.0‰ respectively. The injected CO2 out of the oxycombustion chamber has a δ13CCO2 of –40.0‰, whereas δ13CCO2 value for soils samples is comprised between –15 and –25‰. The Rousse natural gas and the Lacq fuel gas are both characterized by a high He enrichment, and depletion in Ne, Ar and Kr compared to the air values. The oxyfuel combustion process provides a CO2 with the He enrichment of the Lacq fuel gas, and a Ne, Ar and Kr composition reflecting that of the oxygen produced at the Air Separation Unit (ASU). Indeed, Ne is depleted relatively to the air, while Kr is enriched up to tenfold, which results from the cryogenic separation of the air noble gases within the ASU. Soil samples noble gas compositions are equivalent to that of the air. In the light of these results, the compositions of the various end-members involved in this CO2 storage pilot suggest that noble gas compositions produced by oxyfuel process are sufficiently exotic compared to compositions found in nature (reservoir, aquifer and air) to be directly used as tracers of the injected CO2, and to detect and quantify leaks at soil and aquifer levels