CO2 leakage in a shallow aquifer - Observed changes in case of small release

International audienceGeological storage of CO2 in deep saline aquifers is one of the options considered for the mitigation of CO2 emissions into the atmosphere. A deep geological CO2 storage is not expected to leak but potential leakage monitoring is required by legislation, as e.g. the EU Directive relative to Geological Storage of CO2. To ensure that the storage will be permanent and safe for the environment and human health, the legislation require that the CCS operators monitor the injection, the storage complex and if needed the environment to detect any CO2 leakage and its hazardous effects on the environment. Various monitoring methods are available for the monitoring of CO2 storage sites and the environment as listed by the IEA-GHG and the monitoring selection tool. Geophysical based methods have a greater area of investigation but may suffer from insufficient sensitivities to detect small leakages. At the opposite, geochemical monitoring methods may have insufficient investigation area but may be able to detect more subtle changes even if monitoring in deep environments is not straightforward. Leakage detection is not yet well constrained and research efforts and tests are required to gain confidence into monitoring strategies. In the framework of the CIPRES project, funded by the French Research Agency, a shallow CO2 release experiment has been performed in October 2013 in a chalk aquifer from the Paris basin. The Catenoy site has been characterised since March 2013 through several wells set on a straight line oriented along the local flow (see Gombert et al., this conference). Such an experiment is designed to gain confidence in leakage detection in subsurface environments by understanding processes and principles governing seepage occurrence. Contrary to other experiments such as ZERT or CO2FieldLab ones, where gaseous CO2 was injected directly in the water, the injection was done with water saturated with CO2 at atmospheric pressure. 10 m3 of water were pumped from the aquifer, then saturated with 20 kg of food-grade CO2 and injected during 40 hours between 12 and 25 m depth. Daily monitoring of soil gases and water was performed during injection and post-injection phases (2 weeks duration) in the area previously delimited by a tracer test. The aim is to determine if geochemical methods are accurate enough to allow detecting small release in shallow environments. If successful, such an experiment can help to gain confidence in leakage detection. As expected, no change was noticed in the unsaturated zone. The shape of gas concentrations distribution at the surface (CO2, O2, N2, 4He, 222Rn) observed during the injection is strictly similar to the repartition of gas species observed since March 2013. The main process observed is respiration and no change linked to the injection was highlighted, only seasonal effects. Slight changes were observed in the saturated zone. The water was collected at 15 m deep excepted for one stratified borehole where water was sampled at 15 and 18 m. The pH of the injected water was lower (mean value: 5.3±0.1) than the initial pH of the aquifer (7.1-7.2) due to CO2 dissolution. Only two monitoring boreholes set 10 m and 20 m downstream from the injection well may be considered as influenced by the experiment. A probable enrichment in HCO3 linked to interaction of the CO2 saturated water with chalk was noticed, with an enrichment close to +8 to +10% of the initial value. For one borehole the pH value remained nearly stable in relation with pH buffering and in the other borehole a slight decrease was observed (-0.1 to -0.15 pH unit). However this decrease is significant as it is above the instrumental uncertainty of the electrodes. In addition, a slight increase of the electrical conductivity was noticed but it did not exceed +6% compared to baseline data. Such slight changes in the physico-chemical parameters are related to small variations in dissolved elements. Apart from HCO3, the other major ion affected by CO2-water rock-interaction is Ca as the aquifer is mainly composed by calcite. Concentrations increases by +8 to +9% whose amplitude is in agreement with the increase of HCO3. Trace elements were also little affected, the main change concerned Sr (+8 to +10% increase). Modifications occurring during this CO2 release experiment have small amplitude as expected but these results highlight that geochemical methods are able to detect small leakages. Consequently, effects were noticed only during a short period of time. It is not possible to determine if all the injected CO2 has migrated downwards in the direction of flow or if partial lateral migration has occurred, but post-injection monitoring and boreholes logging 12 days after the stop of injection did not reveal any discrepancy in the water columns. On the other hand, the magnitude of the pH change is consistent with the behaviour of the co-injected tracer (dilution ratio ~30). In the perspective of getting more information on the remobilisation of trace metal elements, a push-pull test will be performed in 2014 on the basis of the learning of this first experiment

Hydrochemical impatcs of CO2 leakage on fresh groundwater; A field scale experiment

One of the questions related to the emerging technology for Carbon Geological Storage concerns the risk of CO2 migration beyond the geological storage formation. In the event of leakage toward the surface, the CO2 might affect resources in neighbouring formations (geothermal or mineral resources, groundwater) or even represent a hazard for human activities at the surface or in the subsurface. In view of the preservation of the groundwater resources mainly for human consumption, this project studies the potential hydrogeochemical impacts of CO2 leakage on fresh groundwater quality. One of the objectives is to characterize the bio-geochemical mechanisms that may impair the quality of fresh groundwater resources in case of CO2 leakage. To reach the above mentioned objectives, this project proposes a field experiment to characterize in situ the mechanisms having an impact on water quality and the CO2-water-rock interactions and also to improve the monitoring methodology by controlled CO2 leakage in shallow aquifer. The tests ran on an experimental site in the chalk formation of the Paris Basin. The site is equipped with an appropriate instrumentation and previously characterized (8 piezometers, 25 m deep and 4 piezairs 11 m deep). The injection test was preceded by 6 months of monitoring in order to characterize hydrodynamics and geochemical baselines of the site (groundwater, vadose and soil). Leakage into groundwater is simulated via the injection of a small quantity of food quality CO2 (~20 kg dissolved in 10 m3 of water) in the injection well at a depth of about 20 m. A plume of dissolved CO2 is formed and moves downward according to the direction of groundwater flow and probably by degassing in part to the surface. During the injection test, hydrochemical monitoring of the aquifer is done in situ and by sampling. The parameters monitored in the groundwater are the piezometric head, temperature, pH and electrical conductivity. Analysis on water samples provide chemical elements (major, minor and trace metals), dissolved gases, microbiological diversity and isotopes (13C). The evolution of the composition of the groundwater in terms of major elements, trace elements and isotope signatures is interpreted in terms of geochemical mechanisms, and the water-rock-CO2 interactions are characterised. Modification of the chemical composition of the water in the aquifer due to CO2 injection is assessed in term of groundwater quality i.e. metal element release and the possibility of exceeding references and quality of water for human consumption. One outcome of the CIPRES project will be to highlight mechanisms that can impact groundwater quality when a CO2 leakage occurs and to propose recommendations to prevent or/and eliminate negative effects and any risks to the environment and human health. This project is partially funded by the French Research Agency (ANR)

CO2 leakage in a shallow aquifer – Observed changes in case of small release

AbstractGeological storage of CO2 in deep saline aquifers is one of the options considered for the mitigation of CO2 emissions into the atmosphere. A deep geological CO2 storage is not expected to leak but potential leakage monitoring is required by legislation, as e.g. the EU Directive relative to Geological Storage of CO2. To ensure that the storage will be permanent and safe for the environment and human health, the legislation require that the CCS operators monitor the injection, the storage complex and if needed the environment to detect any CO2 leakage and its hazardous effects on the environment. Various monitoring methods are available for the monitoring of CO2 storage sites and the environment as listed by the IEA-GHG and the monitoring selection tool. Geophysical based methods have a greater area of investigation but may suffer from insufficient sensitivities to detect small leakages. At the opposite, geochemical monitoring methods may have insufficient investigation area but may be able to detect more subtle changes even if monitoring in deep environments is not straightforward. Leakage detection is not yet well constrained and research efforts and tests are required to gain confidence into monitoring strategies.In the framework of the CIPRES project, funded by the French Research Agency, a shallow CO2 release experiment has been performed in October 2013 in a chalk aquifer from the Paris basin. The Catenoy site has been characterised since March 2013 through several wells set on a straight line oriented along the local flow (see Gombert et al., this conference). Such an experiment is designed to gain confidence in leakage detection in subsurface environments by understanding processes and principles governing seepage occurrence. Contrary to other experiments such as ZER

Selection, Instrumentation and Characterization of a Pilot Site for CO2 Leakage Experimentation in a Superficial Aquifer

AbstractCO2 geological storage is one of the options for mitigation of GHG emissions into the atmosphere. Although storage is provided for several millennia, leakage can occur. Therefore the risk that the fugitive CO2 reaches a shallow aquifer cannot be excluded [1]. That is why the consortium launched the research program CIPRES, funded by the French Research Agency, concerning the potential impacts of CO2 leakage on groundwater quality. This program includes the realization of a shallow CO2 release experiment in a carbonated aquifer and its monitoring in the saturated and unsaturated zones, the soil and the soil-atmosphere interface. The experimentation consists in drilling a well into the aquifer, injecting dissolved CO2 in water [2] and tracking its impact downstream. Prior to this experiment, a site had to be selected, instrumented and characterized.Hydrogeological target is the Paris basin chalk which is the largest French aquifer. The selected area is a large parcel, formerly cultivated in intensive monoculture but left fallow for several years, located in Catenoy (Oise) about 50km north of Paris. The geological log shows the chalk is covered by 6-7 m of sands but water table is located at 12-13 m depth, i.e. integrally in the chalk strata.The site has been equipped with 10 wells to characterize the groundwater flow (hydraulic gradient ∼5 10-3). 6 wells are aligned in the groundwater flow direction: the PZ2, planned for CO2 injection, the PZ1 located 20 m upstream and 4 monitoring wells located downstream between 10 and 60 m from PZ2. There are also 4 lateral piezometers located near (PZ7, PZ8) and far (PZ9, PZ10) from the injection site: they are dedicated to the lateral plume. These 25 m depth wells are equipped with tubing fully slotted in the chalk. Alongside, 4 wells dedicated to gas monitoring in unsaturated zone have been drilled at 11m depth.To characterize the site, the following operations were performed prior to the CO2 injection between March and September 2013:•pump test into PZ2 to estimate the hydraulic conductivity (10-3 m.s-1) and the storage coefficient (1.6%); the hydraulic conductivity is higher in the first 3 m of saturated zone (∼5 10-3 m.s-1);•hydrogeochemical baseline with monthly water analysis in each well (physicochemical parameters, major and minor ions, metallic trace elements); electrical conductivity is 714μs.cm-1 and groundwater has a calcium-bicarbonated facies with high nitrate concentration (45mg.l-1) and low-level presence of trace metals;•gas baseline with continuous O2 and CO2 measurement in vadose trough 11 m depth boreholes and measurements campaigns to determine gas concentration in the soil and gas flux on the surface;•flowmeter heatpulse logging at PZ2, PZ3 and PZ4 in static and dynamic conditions; only the area situated from 15 m to 20 m depth is productive and a vertical natural downflow is measured in PZ3 (∼1-2mm.s-1) and PZ4 (1cm.s-1); furthermore, no flow is measured from 20 to 25 m depth; this confirms the vertical anisotropy of the chalky aquifer;Following this experiments, a tracer test has been done in June 2013 from PZ2 with fluorescent tracer (amino-acid G) and a dissolved gas (He), in the way to calibrate the future CO2 injection and its monitoring. 2 m3 of water from the aquifer were pumped the day before the injection and stored in tanks. Then 2kg of tracer were dissolved and water was saturated with He. This water was injected into the PZ2 the next day during 8h. The monitoring was conducted for a month by water sampling, tracer and He analyzes. The peak of fluorescent tracer arrived at the 2nd day following injection in the PZ4 (20 m downstream) but only one week later in the PZ3 (10 m downstream), due to the site anisotropy. Low He concentrations have been detected in the unsaturated zone of PZ4 before PZ3, in correlation with tracer migration.The main result is the existence of an high aquifer anisotropy in such a small area: i) the first 3 m of the saturated zone shows a higher permeability and the last 5 m a lower one, ii) the tracer arrives quickly and with higher concentration at PZ4 located 10 m farther than PZ3. However, the dilution ratio is rather important and may induce, during CO2 leakage experimentation, a slight pH decrease at the downstream wells: in order to increase the impact of the CO2 leakage, we have therefore planned to inject a higher volume (10 m3) of CO2 saturated water

Suivi hydrologique des centres de stockage de déchet-bioréacteurs par mesures géophysiques

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Sci.Terre recherche (751052114) / SudocSudocFranceF

Guidelines for aquifer monitoring programs within the frame of CO2 geological storage

While France is committed to reduce greenhouse gas emissions, the regulatory environment requires that future geological storage sites are chosen so as to ensure environmental protection. Regulations and guidelines are available for geological storage of CO2 but guidelines towards groundwater resources are limited to brief and general recommendations. The collaborative CIPRES project (2012-2015, co-funded by the French Research Agency) was dedicated to the characterization of the potential impacts of CO2 leakage on the groundwater quality in the framework of CO2 geological storage. One main objective aimed at giving clues for the improvement of the existing guidelines in terms of freshwater aquifers monitoring methodology. A guide has been issued, summarizing the existing regulations and guidelines towards aquifers overlying geological storage of CO2 and providing a focused monitoring methodology on groundwater resources. This methodology proposes global aquifer monitoring practices, but also, for each stage of the life cycle of a geological disposal site- - basic parameters to be monitored (pH, electrical conductivity, alkalinity, major ions, DOC, dissolved CO2 groundwater level, temperature, redox potential), recommended for all aquifer in the area of review of the CO2 storage complex+ - specific parameters, which will have to be customized according to the specific context of the assessed case (based on composition of deep fluids, regional geology and hydrogeology, microbiological and geochemical parameters)+ - minimum recommendations in terms of- a) duration- prior to any storage operation, at least two years to acquire the baseline as a reference for monitoring+ b) frequency- at least 2-4 times per year for the baseline acquisitions, and 1-2 times per year during the operation monitoring+ c) and location- in the control aquifer (first aquifer above the geological storage) and vulnerable aquifers (aquifers that may suffer damages)

Gas adsorption capacity of Municipal Solid Waste Incineration Bottom Ashes based materials

International audienceLa présente étude porte sur la détermination des capacités d’adsorption des mâchefers d’incinération d’ordures ménagères (MIOM). Deux échantillons contenant des mâchefers ont été caractérisés vis-à-vis de leur propriétés physico-chimiques et structurales : analyse élémentaire, pH de surface, volume poreux et surface spécifique, observation microscopique couplée spectrométrie X. Les propriétés d’adsorption de ces matériaux vis-à-vis de l’H2S ont été déduites de mesures d’isotherme et cinétique en réacteur batch et leur performance en réacteur continu a été évaluée à partir de courbes de percée réalisées en lit fixe.Les résultats des caractérisations physico-chimique et structurale indiquent que les deux matériaux testés présentent des structures poreuses ainsi que des compositions et chimie de surface très proches et favorables à l’adsorption de gaz acide tel que l’H2S.Les isothermes et cinétiques d’adsorption de l’H2S ont été réalisées pour différentes conditions d’humidité et de température du gaz et pour différentes teneurs en eau des matériaux. Les résultats obtenus montrent l’influence globale de l’eau (humidité de l’air mais surtout teneur en eau de l’échantillon) sur les performances d’adsorption. Ainsi, pour les teneurs en eau élevées, les matériaux présentent des capacités d’adsorption du H2S équivalentes à celles de charbon actif mais pour des temps de contact supérieur. Enfin, des tests d’adsorption de l’H2S réalisés en présence de CH4 dans la phase gaz indiquent qu’il n’y a pas de compétition d’adsorption entre ces 2 composés gazeux.L’étude en lit fixe a permis d’atteindre une bonne épuration initiale de l’H2S et le maintient de ce rendement sur l’ensemble de la durée du test (30 h). La courbe de percée obtenue montre une percée immédiate d’environ 1 % qui pourrait être évitée par l’augmentation de la hauteur de lit mis en œuvre dans la colonne.Ainsi cette étude a permis de mettre en évidence les bonnes performances de matériaux adsorbants à base de MIOM pour le traitement des gaz acides (H2S) pour des conditions opératoires favorisant la présence d’eau et des temps de contact suffisamment longs

Hydrogeochemical impacts of CO2 leakage on fresh groudwater : the CIPRES project

International audienceThe project CIPRES aims to increase our knowledge of the mechanisms involved when CO2 intrudes into freshwater aquifers and, therefore, to study the impact of potential CO2 leakage into groundwater quality. A second objective of the project is to develop a reliable methodology for monitoring the groundwater in the aquifers above the future storage sites. The work will focus on two major aquifers in the Paris Basin: the shallow but highly solicited chalk aquifer and the deep sand aquifer of the Albian. CIPRES project is co-funded by the French Research Agency (ANR). The CIPRES Team is a consortium between BRGM, INERIS, IPGP, ISTO and two companies (VERI and HYDROINVEST)

Leachate recirculation: moisture content assessment by means of a geophysical technique

International audienceBioreactor technology is a waste treatment concept consisting in speeding up the biodegradation of landfilled waste by optimizing its moisture content through leachate recirculation. The measurement of variations in waste moisture content is critical in the design and control of bioreactors. Conventional methods such as direct physical sampling of waste reach their limits due to the interference with the waste matrix. This paper reviews geophysical measurements such as electrical direct current and electromagnetic slingram methods for measuring the electrical conductivity. Electrical conductivity is a property, which is linked to both moisture and temperature and can provide useful indications on the biodegradation environment in the waste mass. The study reviews three site experiments: a first experimentation shows the advantages (correlation between conductive anomaly and water seepage) but also the limits of geophysical interpretation; the two other sites allow the leachate recirculation to be tracked by studying the relative resistivity variation versus time from electrical 2D imaging. Even if some improvements are necessary to consider geophysical measurements as a real bioreactor monitoring tool, results are promising and could lead to the use of electrical 2D imaging in bioreactor designing

Management of aquifer recharge in arid zones under coastal constrains

International audienceThe Managed Aquifer Recharge (MAR) is a broad collection of practices for water resource management, aiming at underground water recharge and storage for its recovery. Climate change, population growth and economic development may be behind the acute tension over water resources, particularly in arid and semi-arid areas. In these areas, recourse to new sources of water has to be considered in order to secure water supply for drinking, irrigation, tourism and domestic using. Artificial groundwater recharge using different water resources (desalted waters, river waters, treated wastewater, etc.) appears as one of major solution to the recurrent issue of water scarcity and supply security. Artificial groundwater recharge is potentially a pragmatic way to store and restore water in the environment allowing to: i) maintain necessary water supply levels, ii) alleviate salt water intrusion into costal aquifers, iii) store water avoiding evaporation as it happens for dams, and iv) make it available at any time for all needs