CO2-DISSOLVED: a Novel Concept Coupling Geological Storage of Dissolved CO2 and Geothermal Heat Recovery – Part 2: Assessment of the Potential Industrial Applicability in France, Germany, and the U.S.A

AbstractThe CO2-DISSOLVED project aims at assessing the technical-economic feasibility of coupling dissolved CO2 storage in a saline aquifer and geothermal heat recovery. It targets specifically low-medium tonnage CO2 emitters (ca. 10-150 kt/yr) because the amount of dissolved CO2 that can be injected into a geothermal saline aquifer is physically limited by the solubility of CO2 in brine. This work makes an inventory of the potential candidates to the CO2-DISSOLVED concept in France, Germany, and the U.S.A. The results evidenced that relatively large geothermal areas match the presence of many industrial sources emitting low rates of CO2, allowing us to conclude on the potential applicability of the concept in these three countries

Improvement of the Calculation Accuracy of Acid Gas Solubility in Deep Reservoir Brines: Application to the Geological Storage of CO

The assessment of the short and long term consequences of CO2 injection in aquifers requires both laboratory experiments and numerical modelling in order to better understand the various physical-chemical processes taking place. Modelling injection in a reservoir, where relatively high temperature (above 50°C), high pressure (several hundreds of bars), and high salinity (greater than that of seawater) conditions are likely to be encountered, thus requires numerical tools able to take into account the specific effects of the various electrolytes dissolved in brines, and the non-ideal behaviour of the CO2 gaseous phase. This study evaluates the consistency of the various corrections (activity, fugacity, influence of pressure on thermodynamic constants) to be taken into account in geochemical models to meet these calculation accuracy requirements. These corrections were implemented in the thermo-kinetic modelling software SCALE2000 (Azaroual et al., 2004a) which was used to check their validity by comparing the calculation results with available experimental observations and other results from CO2 solubility calculation models. An estimation of the relative weight of each of the corrections for a 237 g.l-1 brine (60°C, pCO2 = 200 bar) showed a systematic overestimation (higher than 100%) of CO2 solubility when either salinity (NaCl equivalent) is neglected or gas is considered ideal. The error induced by the NaCl-equivalent approximation compared to real brine is lower (less than 5%). The second part of this study presents an application example of a hypothetical scenario of massive CO2 injection in a carbonated reservoir; data used for the brine composition are actual data (Moldovanyi and Walter, 1992) from the Smackover site (Arkansas, United States). The simulations performed considering a representative elementary volume of saturated bulk rock (porous mineral assemblage saturated with the Smackover brine) with a prescribed constant CO2 pressure of 150 bar, show two distinctively different behaviours whether the system is assumed to be a closed (batch reactor) or an open reactor fed by a constant brine flow rate. In the first case, the calculations performed with SCALE2000 lead to negligible variations in the mineralogy. In the second case, more representative of the dynamical nature of an injection system, the results show major modifications in the mineralogy finally leading to a strong increase in porosity (from 20% initially to 85% after 50 y of simulated time). Further calculations were carried out with SCALE2000, now considering a 1D system constituted of a set of four homogeneous identical reactors connected in series (fluid velocity of 1 m.day-1). With initial and boundary conditions similar to those considered earlier, and prescribing a constant pCO2 in the first reactor only, the results showed that significant dolomite precipitation occurred in the most-downstream reactor hence inducing some CO2 precipitation. Mass balance calculations performed on the four reactors system finally demonstrated a global loss in total mineral carbon with respect to the amounts initially available. However, the evolution trends observed in the most-downstream two reactors indicated that possible trapping might be expected beyond the relatively limited geometrical boundaries considered in the modelled system

Experimental and numerical simulation of the injection of a CO2 saturated solution in a carbonate reservoir: application to the CO2 -DISSOLVED concept combining CO2 geological storage and geothermal heat recovery

International audienceThis study was conducted in the framework of the CO2-DISSOLVED project (Kervévan et al., 2013, 2014), funded by the ANR (French National Research Agency). The CO2-DISSOLVED project proposes to assess the feasibility of a novel CO2 injection strategy in deep saline aquifers, combining injection of dissolved CO2 (instead of supercritical CO2) and recovery of the geothermal heat from the extracted brine. This approach relies on the geothermal doublet technology (commonly used in the Paris Basin, France), where the warm water is extracted at the production well and the cooled brine re-injected in the same aquifer via a second well (injection well). As a consequence, the amount of CO2 that can be injected in the geothermal aquifer is physically limited by CO2 solubility in brine. For that reason and unlike the standard approach (supercritical CO2) which focuses on very large CO2 emitters (ca. > 1 Mt/yr), the CO2-DISSOLVED concept targets specifically low tonnage emitters (ca. 10-150 kt/yr) compatible with a local single doublet facility. Injecting CO2-rich acidified water is expected to induce an enhanced reactivity at the immediate vicinity of the injection well, particularly in presence of carbonated minerals. Similarly, acidified water will be much more aggressive for the well casing and cement than standard cold brine in classical geothermal doublets. However, since this injection option has been much less studied than the standard injection of supercritical CO2, we need to improve our knowledge on these aspects. The work presented in this paper is devoted to fill this gap using a dedicated experimental facility

Integrative Modeling of Caprock Integrity in the Context of CO2 Storage: Evolution of Transport and Geochemical Properties and Impact on Performance and Safety Assessment Modélisation intégrée de l’intégrité des roches de couverture dans le contexte du stockage du CO2 : évolution des propriétés de transport et impact sur les performances et la sûreté du stockage

The objective of the “Géocarbone-Intégrité” project (2005-2008) was to develop a methodology to assess the integrity of the caprock involved in the geological storage of CO2. A specific work package of the project (WP5) was dedicated to the integration of (1) the phenomenology describing the evolution of the storage system with a focus on the mechanisms occurring in the caprock and at the interface with the caprock, and (2) the data obtained from the investigation of petrographical, geomechanical, and geochemical properties, before and after reaction with CO2-rich solutions, performed in the other work packages (WP1 to WP4). This knowledge was introduced in numerical models and specific safety scenarios were defined in order to assess the performance of the CO2 storage system. The results of the modeling show that the injection of CO2 can potentially have a significant effect on the caprock by changing the porosity due to the dissolution and precipitation of minerals, but that the impact is limited to a zone from several decimeters to several meters of the caprock close to the interface with the reservoir depending on whether the supercritical carbon dioxide (SC-CO2) plume enters into the caprock and if fractures are present at this location. The methodology used in this project can be applied to a pilot site for the injection of CO2 in the Paris Basin. A key aspect of the safety of such a facility will be to look at the coupling of geochemical alteration and the evolution of geomechanical properties in the short and medium terms (several hundreds of years). The challenge for the future will be to structure and apply the safety assessment methodology with an operational finality, in order to support the robustness of the transition step to CGS projects at the industrial scale. Le Volet 5 du projet « Géocarbone-Intégrité » visait à intégrer l’ensemble des mécanismes étudiés dans les quatre premiers volets du projet pour une évaluation de performance des couvertures et une étude de sûreté afin de s’assurer de leur préservation et de leur intégrité sur le long terme (de l’ordre du millénaire). L’objectif est, d’une part, d’aboutir à la construction d’un modèle phénoménologique multi-échelle global, puis à un modèle numérique décrivant le confinement du CO2 par les couvertures, et, d’autre part, de déterminer les performances du confinement en identifiant les processus clés et les paramètres les plus influents. Une première partie du programme a consisté en une intégration spatiale de l’ensemble des données phénoménologiques et structurales disponibles à la suite des travaux réalisés dans les différents volets (WP1 à WP4) et à la définition des scénarios types d’évolution du site de stockage (niveaux réservoirs et encaissants). Ce travail a permis de définir les cas tests à prendre en compte et de réaliser les calculs de performance par rapport aux scénarios d’injection et par rapport aux hétérogénéités majeures identifiées dans les niveaux de confinement (notamment les fractures). Les résultats montrent que l’injection de CO2 peut avoir un effet significatif, en altérant la porosité par dissolution et précipitation de minéraux, mais que l’impact est limité dans l’espace, de quelques décimètres à quelques mètres de l’interface réservoir-couverture, selon que la bulle de CO2 supercritique pénètre ou non dans la couverture et selon la présence ou l’absence de fractures. La prise en compte des résultats issus de l’analyse de sensibilité et l’analyse des incertitudes permettra de conduire des calculs de sûreté plus précis. Appliqués au futur site d’injection, ces calculs permettront d’évaluer la pérennité des propriétés de confinement des couvertures et de valider la qualité de confinement du site de stockage de CO2. Il conviendra notamment d’évaluer l’impact du couplage entre les phénomènes géochimiques et géomécaniques sur le court et moyen terme (de l’ordre de la centaine d’années). Le défi pour l’avenir est de structurer et d’appliquer la méthodologie de l’analyse de sûreté, en mettant en avant la finalité opérationnelle, de manière à assurer la robustesse de la transition vers les projets de CGS à l’échelle industrielle

CO2-DISSOLVED: a Novel Concept Coupling Geological Storage of Dissolved CO2 and Geothermal Heat Recovery Part 3: Design of the MIRAGES-2 Experimental Device Dedicated to the Study of the Geochemical Water-Rock Interactions Triggered by CO2 Laden Brine Injection.

International audienceThe CO2-DISSOLVED project aims at assessing the feasibility of the coupling between dissolved CO2 storage in aquifer and geothermal heat recovery. The MIRAGES-2 experimental setup has been designed to study, at the centimeter scale and under relevant conditions of pressure and temperature, the chemical interactions in the near-injection well area between the reservoir rock, the cement phases, and the corrosive CO2-rich solution. This original experimental setup allows performing flow-through experiments with continuous in-situ data acquisition of pressure, temperature, flow rate, pH, and dissolved CO2 concentration. The datasets acquired will be further interpreted with the help of geochemical models, in order to better understand the effects of the key physical-chemical processes involved

Integrative Modeling of Caprock Integrity in the Context of CO

The objective of the “Géocarbone-Intégrité” project (2005-2008) was to develop a methodology to assess the integrity of the caprock involved in the geological storage of CO2. A specific work package of the project (WP5) was dedicated to the integration of (1) the phenomenology describing the evolution of the storage system with a focus on the mechanisms occurring in the caprock and at the interface with the caprock, and (2) the data obtained from the investigation of petrographical, geomechanical, and geochemical properties, before and after reaction with CO2-rich solutions, performed in the other work packages (WP1 to WP4). This knowledge was introduced in numerical models and specific safety scenarios were defined in order to assess the performance of the CO2 storage system. The results of the modeling show that the injection of CO2 can potentially have a significant effect on the caprock by changing the porosity due to the dissolution and precipitation of minerals, but that the impact is limited to a zone from several decimeters to several meters of the caprock close to the interface with the reservoir depending on whether the supercritical carbon dioxide (SC-CO2) plume enters into the caprock and if fractures are present at this location. The methodology used in this project can be applied to a pilot site for the injection of CO2 in the Paris Basin. A key aspect of the safety of such a facility will be to look at the coupling of geochemical alteration and the evolution of geomechanical properties in the short and medium terms (several hundreds of years). The challenge for the future will be to structure and apply the safety assessment methodology with an operational finality, in order to support the robustness of the transition step to CGS projects at the industrial scale