Evaluating sealing efficiency of caprocks for CO2 storage: an overview of the Geocarbone Integrity program and results

8 pagesInternational audienceThe objectives of the Geocarbone-Integrity program are to develop techniques, methodologies and knowledge concerning the long term confinement of CO2 in geological storage. Linked to other French programs such as Geocarbone Injectivity or Picoref, it is an integrated approach involving geochemistry, petrophysics, geology and geomechanics. Different scales must be considered in order to describe caprocks: from the pore or grain scale in petrophysics and geochemistry, to regional scale in geology and geomechanics. The program focused on a specific site of the Paris basin but the methodologies developed are general and can be applied elsewhere

METSTOR: A GIS to look for potential CO2 storage zones in France

AbstractThe METSTOR project offers a methodology to look for potentially interesting CO2 storage areas in France at the initial stage, before the “site selection” step. Our tool, embodied in a Geographic Information System, is based on an interactive map of CO2 storage capacities. Other relevant information layers are included. The geographic layers are complemented with a series of online technical notices. It seems to be the first open online GIS that offers policy makers, businesses and the public at large an integrated access to that necessary information. Our prototype, limited mainly to the Paris Basin, is released online at www.metstor.fr

Technical challenges in characterization of future CO2 storage site in a deep saline aquifer in the Paris basin. Lessons learned from practical application of site selection methodology

AbstractTo ensure safe behavior during the whole lifetime of the geological storage of CO2, site selection and its characterization are essential corner stones. This paper presents the different milestones and the results of each step of the site characterization implemented on a potential storage site in the Triassic deep saline aquifer of the Paris Basin. It addresses a well known theory and practical aspects and challenges of the first phase of real site identification carried out by Veolia Environnement and Geogreen.The initial static and dynamic characterization of the storage complex will mainly rely on available public or proprietary data. Different challenges related to the gathering and validation of existing data are discussed. The characterization methodology should aim at re-interpreting the available data in order to populate a dynamic model at semi-regional scale of the storage complex.2D Seismic data reprocessing made it possible to determine the local structure of the storage. Regional structural information must also been considered since industrial scale injection impacts a significant area with respect to overpressure extension. To complete the storage complex description, upper laying structures and aquifers must be adequately described up to the ground level. When elaborating such a 3D model, data consistency at the different scales should be carefully checked.Facies variations, porosity and both vertical and horizontal permeabilities will control storage capacity and well injectivity. Thus, an extensive log analysis is a major step in the characterization methodology. When available, core samples and flow tests must also be reconsidered to enhance the model quality. Furthermore, petrophysical interpretation of logs will improve site characterization and enable mineral trapping assessment. The consistent re-interpretation of available well logs will ensure proper site characterization in terms of reservoir and containment. Some examples are provided to illustrate the relevance of re-interpretation work.Building a 3-D geological model is a major integrating step of the available dataset on the area of interest both in terms of structure and heterogeneities at different scales (facies, mineral, petrophysical …). At this stage, the different assumptions should be carefully revisited in light of the available data. The geological uncertainties can then be estimated using a statistical approach, which highlights key petrophysical characteristics of the storage along with main risks that need to be assessed.The final step in the characterization methodology includes a dynamic assessment of the short term effects on injectivity and capacity, and of long term trapping mechanism. On the short term, potential interference with other sub-surface activities needs to be investigated along with the potential migration pathways (existing wells and faults). Models were elaborated at different scales. A near-wellbore model helped to estimate chemical induced effects. A storage site model helped to estimate overpressure and CO2 plume behaviors, and a model larger than the storage complex helped to identify migration pathways and constraint boundary conditions. Different assumptions and operational constraints were supposed to ensure the robustness of different injection scenarios. The results of corresponding dynamic simulations are presented and discussed

Evaluating Sealing Efficiency of Caprocks for CO2 Storage: an Overview of the Geocarbone-Integrity Program and Results Évaluation de l’intégrité des couvertures d’un stockage de CO2 : un aperçu du programme Géocarbone-Intégrité et de ses résultats

An overview of the three-year program and results of the Geocarbone-Integrity French project is given. It focused on the development of experimental and numerical methodologies to assess the integrity of underground CO2 storage at various scales. The primary criteria in the selection of a caprock formation for CO2 storage purposes are the thickness and permeability of the formation. Local and limited migration of CO2 into the caprock due to insufficient capillary entry pressure has been studied as a probable scenario. At a large scale, caprock characterization requires at least seismic profiles to identify lateral continuity. When well-logging data are available, simple rules based on clay content can be used to estimate thicknesses. For the formation considered, the geochemical reactivity to CO2 was small, making the reaction path difficult to identify. Similarly, artificial alterations of samples representing extreme situations had little impact on geomechanical properties. Finally, with realistic overpressure due to injection, shear fracture reactivation criteria are not reached and migration of CO2 either by diffusion or by two-phase flow within the first meters of the caprock produce mostly a decrease in porosity by precipitation, and very locally an increase in porosity by dissolution. Un aperçu du programme et des résultats du projet multipartenaire Géocarbone-Intégrité est donné. Il concerne le développement de méthodes expérimentales et numériques pour évaluer l'intégrité d'un stockage de CO2. Les critères essentiels d'une couverture sont l'épaisseur de la formation et sa perméabilité. Une migration locale et limitée du CO2 dans la couverture due à une pression capillaire d'entrée insuffisante est étudiée dans ce travail. À grande échelle, des profils sismiques sont nécessaires pour caractériser la continuité d'une couverture. Quand on dispose de données de puits, des critères simples pour estimer l'argilosité peuvent être utilisés. On montre également que les techniques de lithosismique peuvent être appliquées aux couvertures. Pour les formations considérées, nous n'avons pas observé au laboratoire de réactivité géochimique importante, ni d'effet marquant sur les propriétés mécaniques. Des simulations hydromécaniques à grande échelle montrent que les critères de rupture ou de réactivation de fractures préexistantes ne sont pas satisfaits. Des simulations de transport réactif par diffusion et écoulement diphasique dans la couverture montrent une migration du CO2 sur une dizaine de mètres au plus et une baisse de la porosité par précipitation, et localement une augmentation de la porosité par dissolution

METSTOR : a GIS to look for potential CO2 storage zones in France

The METSTOR project offers a methodology to look for potentially interesting CO2 storage areas in France at the initial stage, before the "site selection" step. Our tool, embodied in a Geographic Information System, is based on an interactive map of CO2 storage capacities. Other relevant information layers are included. The geographic layers are complemented with a series of online technical notices. It seems to be the first open online GIS that offers policy makers, businesses and the public at large an integrated access to that necessary information. Our prototype, limited mainly to the Paris Basin, is released online at www.metstor.f

Selection and Characterization of Geological Sites able to Host a Pilot-Scale CO2 Storage in the Paris Basin (GéoCarbone-PICOREF) Choix et caractérisation de sites géologiques propices à l’installation d’un pilote pour le stockage de CO2 dans le bassin de Paris (GéoCarbone-PICOREF)

The objective of the GéoCarbone-PICOREF project was to select and characterize geological sites where CO2 storage in permeable reservoir could be tested at the pilot scale. Both options of storage in deep saline aquifer and in depleted hydrocarbon field were considered. The typical size envisioned for the pilot was 100 kt CO2 per year. GéoCarbone-PICOREF initially focused on a “Regional Domain”, ca. 200 × 150 km, in the Paris Basin. It was attractive for the following reasons: detailed geological data is available, due to 50 years of petroleum exploration; basin-scale deep saline aquifers are present, with a preliminary estimate of storage capacity which is at the Gt CO2 level, namely the carbonate Oolithe Blanche Formation, of Middle Jurassic age, generally located between 1500 and 1800 m depths in the studied area, and several sandstone formations of Triassic age, located between 2000 and 3000 m; several depleted oil fields exist: although offering storage capacities at a much lower level, they do represent very well constrained geological environments, with proven sealing properties; several sources of pure CO2 were identified in the area, at a flow rate compatible with the pilot size, that would avoid capture costs. 750 km of seismic lines were reprocessed and organized in six sections fitted on well logs. This first dataset provided improved representations of: the gross features of the considered aquifers in the Regional Domain; the structural scheme; lateral continuity of the sealing cap rocks. An inventory of the environmental characteristics was also made, including human occupancy, protected areas, water resource, natural hazards, potential conflicts of use with other resources of the subsurface, etc. From all these criteria, a more restricted geographical domain named the “Sector”, ca. 70 × 70 km, was chosen, the most appropriate for further selection of storage site(s). The geological characterization of the Sector has been as exhaustive as possible, with the reprocessing of additional 450 km of seismic lines, and the collection of a complete well-data base (146 petroleum wells). At this scale a relatively detailed characterization of the sedimentary layers could be done, in particular the formations potentially rich in aquifer units. For the Middle Jurassic carbonates observations were made on analogue sediments outcropping 150 km to the east of the Sector. A geological and numerical 3-D representation of the whole sedimentary pile of the Sector area was built. It forms a basis for constructing grids used by codes able to simulate various processes induced by CO2 injection (displacement of the fluids, pressure build-up and release, mechanical deformation, mineral interactions, control of the parameters used to check the local sealing efficiency, etc.). In parallel with that work on aquifers, GéoCarbone-PICOREF has access to all the petroleum data, including production data and reservoir modelling, of the Saint-Martin de Bossenay oil field, localized in the eastern part of the Sector. This was an opportunity to apply a comparable methodology and to test the capabilities of modelling codes to the specific case of a depleted hydrocarbon field, and to show some of the advantages of such a context with respect to a pilot-scale CO2 injection. <br> Le projet GéoCarbone-PICOREF avait pour objectif de caractériser des sites propices à la réalisation d’un pilote national de stockage du CO2 en réservoir géologique perméable. Deux types de réservoir ont été examinés : des aquifères profonds, et des gisements d’hydrocarbures en voie d’épuisement. Les sites devaient être choisis de manière que le pilote puisse tester des problématiques qui concernent les futurs stockages de grande taille. GéoCarbone-PICOREF a d’abord sélectionné une “Zone régionale” d’environ 200 × 150 km dans le bassin de Paris, qui présente les avantages suivants : l’information géologique y est largement disponible, grâce aux travaux d’exploration pétrolière depuis 50 ans ; de grands aquifères salins y sont présents, dans les carbonates du Jurassique moyen situés en général entre 1500 et 1800 m de profondeur, et dans les formations gréseuses du Trias, entre 2000 et 3000 m; il existe plusieurs gisements d’hydrocarbures en voie d’épuisement : offrant des capacités de stockage moindres, leur intérêt est d’être bien connus sur le plan géologique et d’être dotés de bonnes qualités en termes de piégeage géologique. Après avoir retraité 750 km de lignes sismiques, et avoir assemblé celles-ci selon six coupes calées sur des données de puits, on a précisé sur la Zone régionale : les grandes caractéristiques des aquifères concernés ; la localisation des failles ; la continuité des couches très peu perméables situées au-dessus des réservoirs. Ces études ont permis de choisir un “Secteur”, d’environ 70 × 70 km, au sein duquel on a ensuite affiné l’investigation géologique : 450 km supplémentaires de lignes sismiques, collecte exhaustive des données de puits, caractérisation fine des propriétés réservoir. Des observations de terrain ont été faites sur des roches équivalentes portées à l’affleurement. Un modèle géologique et informatique complet du Secteur a été construit à partir de ces données. Il permet de générer des maillages pour la simulation de divers comportements attendus suite à l’injection de CO2 (déplacement et dissipation du gaz dans les couches réservoir, modification des pressions et des contraintes, déformation mécanique des terrains, interaction entre l’eau acidifiée et les minéraux, etc.). Parallèlement, le projet a pu avoir accès à toutes les données pétrolières du gisement de Saint-Martin de Bossenay, situé dans la partie Est du Secteur. Grâce à cette opportunité, on a montré quel parti pouvait être tiré, pour un pilote, d’un gisement d’hydrocarbures déjà largement exploité, doté d’un piège géologique qui a retenu des hydrocarbures pendant des millions d’années, et sur lequel un opérateur industriel dispose d’une infrastructure et d’un savoir-faire