Quantitative monitoring of dissolved gases in a flooded borehole: calibration of the analytical tools

Gas monitoring is a prerequisite to understanding the exchange, diffusion, and migration processes of natural gases within underground environments, which are involved in several applications such as geological sequestration of CO2. In this study, three different techniques (micro-GC, infrared, and Raman spectroscopies) were deployed on an experimental flooded borehole for monitoring purposes after CO2 injection. The aim was to develop a real-time chemical monitoring device to follow dissolved gas concentrations by measurements in water inside the borehole but also at the surface through a gas collection system in equilibrium with the borehole water. However, all three techniques must be calibrated to provide the most accurate quantitative data. For this, a first step of calibration in the laboratory was carried out. A new calibrations were required to determine partial pressure and/or concentrations of gases in water or in the gas collection system. For gas phase analysis, micro-GC, FTIR spectroscopy, and Raman spectroscopy were compared. New calibration of the micro-GC was done for CO2, CH4, and N2 with uncertainty from ±100 ppm to 1.5 mol% depending on the bulk concentration and the type of gas. The FTIR and Raman spectrometers were previously calibrated for CO2, and CO2, N2, O2, CH4, and H2O, respectively with an accuracy of 1–6% depending on concentration scale, gas and spectrometer. Dissolved CO2 in water was measured using a Raman spectrometer equipped with an immersion probe. The uncertainty on the predicted dissolved CO2 concentration and partial pressure was ±0.003 mol·kg−1 and ±0.05 bar, respectively

Role of Impurities on CO2 Injection: Experimental and Numerical Simulations of Thermodynamic Properties of Water-salt-gas Mixtures (CO2 + Co-injected Gases) Under Geological Storage Conditions

International audienceRole of impurities on CO 2 injection: experimental and numerical simulations of thermodynamic properties of water-salt-gas mixtures (CO 2 + co-injected gases) under geological storage conditions Abstract Regarding the hydrocarbon source and CO 2 capture processes, fuel gas from boilers may be accompanied by so-called "annex gases" which could be co-injected in a geological storage. These gases, such as SOx, NOx, or oxygen for instance, are likely to interact with reservoir fluids and rocks and well materials (casing and cement) and could potentially affect the safety of the storage. However, there are currently only few data on the behaviour of such gas mixtures, as well as on their chemical reactivity, especially in the presence of water. One reason for this lack comes from the difficulty in handling because of their dangerousness and their chemical reactivity. Therefore, the purpose of the Gaz Annexes was to develop new experimental and analytical protocols in order to acquire new thermodynamic data on these annex gases, in fine for predicting the behaviour of a geological storage of CO 2 + co-injected gases in the short, medium and long terms. This paper presents Gaz Annexes concerning acquisition of PVT experimental and pseudo-experimental data to adjust and validate thermodynamic models for water / gas / salts mixtures as well as the possible influence of SO 2 and NO on the geological storage of CO 2. The Gaz Annexes s new insights for the establishment of recommendations concerning acceptable content of annex gases

Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples

Funder: NCI U24CA211006Abstract: The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF < 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological divergences between two reproducible somatic variant detection efforts

Modélisation expérimentale de l’injection de solutions enrichies en CO₂ dans un doublet géothermique. Étude des impacts géochimiques en proche puits

This work was conducted in the framework of the technical assessment of a novel Carbon Capture and Storage (CCS) concept integrating aqueous dissolution of CO2 and injection via a geothermal doublet. This study focuses on i) the quantification and modelling of the hydrodynamic and geochemical impact induced by the injection of a CO2-laden solution in a reservoir rock and ii) the evaluation of long term integrity of the well materials (cement, steel casing) in order to ensure a safe injection protocol. A dedicated experimental device named MIRAGES.2 was developed to mimic, at the lab scale, the continuous radial injection of a CO2-enriched solution under realistic conditions of a geological reservoir. The miniature well consists in a steel tube that is cemented to the core plug with a class G Portland cement. The test bench is divided in two parts: the first one is devoted to the CO2-solution mixing process, and the second one enables to perform the injection of the solution in the core-plug. In addition, the implementation of original in situ measurement techniques (in-situ HP/HT Raman and pH probes, flowmeter) was carried out in order to ensure optimal acquisition of physical and chemical data (pressure, temperature, pH, concentrations of different species in solution...) during the experiments. A method of image processing acquired on post-experimental samples by X-ray micro-tomography has been developed. This technique revealed the 3D architecture of the mesoscopic porous network. This experimental protocol revealed the physicochemical evolution of: the different interfaces between cement and steel, and between cement and reservoir ; the near-well region of the reservoir ; The injected fluid. A set of 7 experiments was performed. The injection duration (12 h, 24 h, 2.5 d, 10 d and 21 d), the fluid salinity and the core drilling inclination with respect to the bedding were investigated. The experiments demonstrate the non-uniform propagation of the acidic solution from the injection point in the form of preferential pathways called « wormholes ». Once a single wormhole breaks through the core-plug, all the other competing wormholes stop growing and their density tend to decrease as the solution is injected. Despite a predominant localized phenomenon, changes in petrophysical properties of the rock in regions far from the wormholes was observed. Following the continuous renewal of the acidic solution, a uniform dissolution in the upper part of the injection well was also highlighted. Roughness surface measurements coupled with microscopic observations have revealed the presence of calcite precipitation which induces the clogging of secondary wormholes. Cement ageing in contact with the reactive solution induces localized chemical imbalances. Changes in magnesium concentration, inhibitor of calcite precipitation, released during cement alteration, govern the local calcite saturation states of the interstitial solution. These phenomena could explain the observed precipitation in a medium mainly undersaturated with respect to the calcite. The experiments also demonstrated the important role of the salinity of the injected solution, which dissolves up to five times more host rock than a freshwater solution. Finally, a multi-scale structural study was carried out and established the close relationship between the distribution of structural defects generated by regional tectonics and the orientation of the dissolution networks observed in our experiments. These results refine the analysis and assessment of environmental impacts and risks in the context of the CO2 injection in a geothermal doublet. They demonstrate the discontinuities present in the rock control the dissolution paths at the reservoir scale.Les travaux réalisés s’inscrivent dans le cadre de l’étude de faisabilité d’un concept hybride couplant l’exploitation d’énergie géothermique et le stockage géologique de CO2 sous forme dissoute. Ils visent à i) quantifier et simuler l’impact hydrodynamique et géochimique de l’injection dans une roche carbonatée de la solution enrichie en CO2 et ii) déterminer le comportement des matériaux constituant le puits d’injection (ciment, casing acier) afin de s’assurer de la sécurisation de l’injection. Le développement d’un dispositif expérimental innovant appelé MIRAGES-2 a permis de reproduire à l’échelle du laboratoire l’injection "radiale" d’une solution saturée en CO2 dans un puits miniature scellé dans un échantillon de roche dans les conditions de pression et de température attendues dans le réservoir géothermique. Ce banc est composé d’un dispositif amont de solubilisation du CO2 dans l’eau de formation et d’un dispositif aval simulant l’injection dans le modèle réduit de puits. En plus des contrôles éprouvés de la pression et de la température, des outils originaux (sonde Raman HP/HT, sonde pH HP/HT, débitmètre) permettant l'acquisition in situ de données physico-chimiques au cours des expériences (concentrations des différentes espèces en solution, pH, débit) ont été intégrés et validés. Enfin, une méthode de traitement d’images acquises sur les échantillons post-expérimentaux par la technique de micro-tomographie aux rayons X a permis une reconstruction 3D de l’architecture du réseau poreux mésoscopiques. Ce protocole expérimental a alors permis le suivi de l’évolution physico-chimique : des différentes interfaces ciment/acier, ciment/réservoir ; de la région proche-puits du réservoir ; du fluide injecté. Une série de 7 expériences a été réalisée afin d’étudier les effets des durées d’injection (12h, 24h, 2.5j, 10j, 21j), de la salinité de la solution injectée et de l’orientation du puits d’injection par rapport à la stratification de la roche. Les expériences ont permis de montrer le développement et la propagation, à partir du point d’injection, d’une dissolution non-uniforme de la roche carbonatée sous forme de chemins préférentiels appelés « wormholes » et dont la densité tend à décroître globalement après le perçage de la carotte. Malgré la prédominance de ce phénomène localisé, une évolution des caractéristiques pétrophysiques de la roche dans des régions éloignées des wormholes a été observée. Suite au renouvèlement continu de la solution acidifiée, une dissolution uniforme en partie haute de puits a été mise en évidence. L’analyse de la rugosité de surface des wormholes couplée à des observations microscopiques a montré la présence de précipitations de calcite qui conduisent à la fermeture de wormholes secondaires. L’étude du vieillissement du ciment au contact de la solution réactive montre qu’il est à l’origine de déséquilibres chimiques localisés. Les valeurs de concentration en magnésium, inhibiteur de la précipitation de la calcite et principalement liées à l’altération du ciment gouvernent les états locaux de saturation de la solution interstitielle vis-à-vis de la calcite. Elles seraient donc à l’origine des précipitations observées dans un milieu pourtant principalement sous-saturé vis-à-vis de la calcite. Les expériences ont également démontré le rôle important de la salinité de la solution injectée qui permet de dissoudre jusqu’à cinq fois plus la roche encaissante qu’une solution d’eau douce. Enfin, une étude structurale multi-échelle a été menée et a établi la relation étroite entre la distribution des défauts structuraux générés par la tectonique régionale et l’orientation des réseaux de dissolution observés dans nos expériences. Ces résultats affinent l’analyse et l’évaluation des impacts et des risques environnementaux dans le contexte du projet étudié. Ils permettent de définir le rôle des discontinuités présentes dans la roche et leur contrôle sur les chemins de dissolution à l’échelle du réservoir

Experimental Mutual Solubilities of CO 2 and H 2 O in Pure Water and NaCl Solutions

International audienceSolubility measurements in conditions relevant to CO2 geological storage are sparse, especially solubility data of water in the CO2-rich phase. New data are acquired by in situ Raman spectroscopy in NaCl aqueous. An effect of NaCl concentration is observed on calibration curves in the H2O-rich phase: the slope of the fitted curve ICO2/IH2O = f(sCO2) is equal to 4.97, 4.25, and 3.93 at 0, 1, and 2 M NaCl, respectively. On the contrary, the Raman signal in the CO2-rich phase is not affected by salinity. The slope of the fitted curve ACO2/AH2O = f(yCO2/yH2O) is equal to 1.72 whatever the NaCl concentration

Measuring mutual solubility in the H2O–CO2 system up to 200 bar and 100°C by in situ Raman spectroscopy

International audienceThe solubility control in the H2O–CO2system under high pressure is of prime interest in numerousgeochemical systems from hydrothermal fluids to CO2geological storage. However, the number of exper-imental data is scarce in the range of interest of geological storage, especially in the CO2-rich phase. A newexperimental device was built to measure mutual solubility in the CO2–H2O system without samplingby coupling a batch reactor with Raman immersion probes. The system was first calibrated by measuringthe solubility of CO2in water at 100◦C. The results were provided with an accuracy of a few % between40 bar and 200 bar and in agreement with other published experimental data sets and models. The lin-ear correlation between Raman peak intensity and CO2solubility in the aqueous phase was then usedto provide new experimental data of CO2solubility in water at 65◦C from 3 bar to 200 bar. The Ramandata of the CO2-rich phase or supercritical phase are compared to a thermodynamic models and the fewexperimental data available in literature to provide a new data set of H2O–CO2mutual solubility at 100◦Cand up to 200 bar

Structural Control of a Dissolution Network in a Limestone Reservoir Forced by Radial Injection of CO2 Saturated Solution: Experimental Results Coupled with X-ray Computed Tomography

This study was conducted in the framework of the PILOT CO2-DISSOLVED project, which provides an additional approach for CO2 sequestration, with the aims of capturing, injecting, and locally storing the CO2 after being dissolved in brine. The brine acidity is expected to induce chemical reactions with the mineral phase of the host reservoir. A set of continuous radial CO2 flow experiments was performed on cylindrical carbonate rock samples under geological storage conditions. The objective was to interpret the dissolution network morphology and orientation involved. To explore the three-dimensional architecture of dissolution arrays and their connection integrity within core samples, we used computed tomography. A structural investigation at different scales revealed the impact of the rock heterogeneity on the dissolution pathways. The initial strike of the observed mesoscopic wormholes appears to be parallel to dilatational fractures, with a subsequent change in major trends of dissolution along master shears or, more specifically, a combination of synthetic shears and secondary synthetic shears. Antithetic shears organize themselves as slickolitic surfaces, which may be fluid-flow barriers due to different mineralogy, thus affecting the permeability distribution-wormhole growth geometry induced by CO2-rich solutions

Geochemical effects of an oxycombustion stream containing SO2 and O-2 on carbonate rocks in the context of CO2 storage

International audienceThis paper describes the effects of the injection of a CO2-dominated gas mixture into a geologic reservoir rock through experimental work in the context of limiting greenhouse gas emissions into the atmosphere. The injected gas mixture consists of the exhaust fumes from an oxyboiler without desulphurisation with the following mole fraction composition: CO2 = 0.82, SO2 = 0.04, O-2 = 0.04, N-2 = 0.04 and Ar = 0.06. Corresponding experiments using pure CO2 and N-2 were performed as a benchmark. The rock sample was obtained by drilling to a depth of 4600 m into a low-porosity dolostone reservoir containing micrometric to centimetric fractures in the south-west of France (northern Pyrenees). The fracture network represents the primary volume available for CO2 storage and is partly filled with dolomite separated from the rock matrix by a thin layer of calcite covering the wall rocks. Experimental reactivity of the rock was tested in 2-cm(3) batch reactors in the presence of saline water (25 g/l NaCl) and a gas phase (pure N-2, pure CO2 and gas mixture). Chemical analyses of the reacting solutions indicated that the mineralogic assemblage during exposure to pure CO2 was in equilibrium with the aqueous solution. Raman analyses of the gas phase revealed only the presence of CO2. Optical and electronic microscopy of the resultant solid phases indicated partial dissolution of carbonates and oxidation of the pyrite surfaces. In the presence of the gas mixture, important mineralogic alteration occurred together with the consumption of half of the O-2 and total consumption of the SO2. This high reactivity with the gas mixture leads to the complete dissolution of calcite and partial dissolution of dolomite and the precipitation of anhydrite and barite, particularly in the zones where the calcite was initially present. Similarly, pyrite was completely oxidised to hematite. Analyses of the rock samples indicated partial alteration of the clay minerals in the matrix to potassic beidellite in the experiment involving pure CO2 and solely to vermiculites in the gas mixture experiment. In conclusion, the presence of SO2 in the injection stream associated with the presence of O-2 results in an early strong acidification of the water, which was buffered by the significant reactivity of the carbonates (dissolution of all of the calcite and 6% of the dolomite) and partial alteration of the clay minerals (87% of illite and 100% of smectite) to vermiculites. Pyrite and aqueous Fe from clays were completely oxidised by O-2, resulting in hematite and Fe3+. The mineralogic alteration and consequent volume changes under experimental conditions led to a slight increase in the porosity of the dolomite matrix and an average pore volume loss of 11% in the fractures caused by the replacement of calcite with anhydrite. Due to its high reactivity with carbonate, SO2 can react early during the injection phase. The spatial distribution of calcite in the fractures of the reservoir has to be considered as one of the primary parameters controlling the evolution of the reservoir in terms of injectivity and petrophysical properties, particularly in the zone near the injection wellbores. The integrity of the calcite-rich caprock is, however, ensured due to its thickness (more than 1000 m) and its calcite content, which leads to pH buffering and anhydrite precipitation, which, in turn, induces a porosity reduction and a possible coating of the rock formation

Numerical simulation of the injection of a CO 2 saturated solution in a limestone sample

International audienceThe CO2-DISSOLVED project [1] proposes to assess the feasibility of a novel CO2 injection strategy in deep saline aquifers, combining injection of dissolved 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). The amount of CO2 that can be injected in the geothermal aquifer is physically limited by CO2 solubility in brine. 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. In order to improve our knowledge on these aspects a dedicated experimental facility, the MIRAGES-2 experimental device designed by GeoRessources [2] was used. MIRAGES-2 is designed for injection of a CO2-rich aqueous solution in an injection well at the 1/20th scale. The well is made of a steel tube that is fixed to the core plug with a class G Portland cement. Well materials (cement and steel) and reservoir rocks (limestone) are used to reproduce elements and interfaces present in real conditions

Experimental Simulation of the Caprock/Cement Interface Behaviour at High Temperature and High CO2-Pressure: the Sandwich Experiment

International audienceThe reactivity of well materials, individually considered in the case of geological storage of CO2, is well documented. However, a lack of data concerning the reactivity of the interfaces between these materials still remains. This observation led the G2R laboratory (Université de Lorraine) to develop an original experimental set-up called "Sandwich". It consists in performing CO2-ageing of composite materials. The reactivity of a caprock/cement interface was thus examined after 30 days of exposure to CO2 at a temperature of 80°C and a pressure of 100 bar. A SEM study showed a fracturing of the interface, which was partially filled with carbonate minerals. The comparison with the blank samples aged in the presence of N2 leads to the conclusion that the CO2 is responsible for the fracturing, due to the precipitation of carbonates and the induced crystallization pressure