Carbon dioxide (CO2) from energy consumption is a primary source of greenhouse gases. Injection of CO2 from power plants in coalbed reservoirs is a plausible method for reducing atmospheric emissions, and it can have the additional benefit of enhancing methane recovery from coal. Most previous studies have evaluated the merits of CO2 disposal in high-rank coals. Low-rank coals in the Gulf Coastal plain, specifically in Texas, are possible targets for CO2 sequestration and enhanced methane production. This research determines the technical feasibility of CO2 sequestration in Texas low-rank coals in the Wilcox Group in east-central Texas and the potential for enhanced coalbed methane (ECBM) recovery as an added benefit of sequestration. It includes deterministic and probabilistic simulation studies and evaluates both CO2 and flue gas injection scenarios. Probabilistic simulation results of 100% CO2 injection in an 80-acre 5-spot pattern indicate that these coals with average net thickness of 20 ft can store 1.27 to 2.25 Bcf of CO2 at depths of 6,200 ft, with an ECBM recovery of 0.48 to 0.85 Bcf. Simulation results of 50% CO2 - 50% N2 injection in the same 80-acre 5-spot pattern indicate that these coals can store 0.86 to 1.52 Bcf of CO2, with an ECBM recovery of 0.62 to 1.10 Bcf. Simulation results of flue gas injection (87% N2 - 13% CO2) indicate that these same coals can store 0.34 to 0.59 Bcf of CO2, with an ECBM recovery of 0.68 to 1.20 Bcf. Methane resources and CO2 sequestration potential of low-rank coals of the Wilcox Group Lower Calvert Bluff (LCB) formation in east-central Texas are significant. Resources from LCB low-rank coals in the Wilcox Group in east-central Texas are estimated to be between 6.3 and 13.6 Tcf of methane, with a potential sequestration capacity of 1,570 to 2,690 million tons of CO2. Sequestration capacity of the LCB lowrank coals in the Wilcox Group in east-central Texas equates to be between 34 and 59 years of emissions from six power plants in this area. These technical results, combined with attractive economic conditions and close proximity of many CO2 point sources near unmineable coalbeds, could generate significant projects for CO2 sequestration and ECBM production in Texas low-rank coals.

abstract: Global warming resulted from greenhouse gases emission has received widespread attention. Meanwhile, it is required to explore renewable and environmentally friendly energy sources due to the severe pollution of the environment caused by fossil fuel combustion. In order to realize a substantial adsorption process to resolve the environmental issues, the development of new adsorbents with improved properties has become the most critical issue. This dissertation presents the work of four individual but related studies on systematic characterization and process simulations of novel adsorbents with superior adsorption properties. A perovskite oxide material, La0.1Sr0.9Co0.9Fe0.1O3-δ (LSCF1991), was investigated first for high-temperature air separation. The oxygen sorption/desorption behavior of LSCF1991 was studied by thermogravimetric analysis (TGA) and fixed-bed breakthrough experiments. A parametric study was performed to design and optimize the operating parameters of the high-temperature air separation process by pressure swing adsorption (PSA). The results have shown great potential for applying LSCF1991 to the high-temperature air separation due to its excellent separation performance and low energy requirement. Research on using nanostructured zeolite NaX (NZ) as adsorbents for CO2 capture was subsequently conducted. The CO2/N2 adsorption characterizations indicated that the NZ samples lead to enhanced adsorption properties compared with the commercial zeolites (MZ). From the two-bed six-step PSA simulation, NZ saved around 30% energy over MZ for CO2 capture and recovery while achieving a higher CO2 purity and productivity. A unique screening method was developed for efficient evaluation of adsorbents for PSA processes. In the case study, 47 novel adsorbents have been screened for coal bed methane (CBM) recovery. The adsorbents went through scoring-based prescreening, PSA simulation, and optimization. The process performance indicators were correlated with the adsorption selectivity and capacities, which provides new insights for predicting the PSA performance. A new medium-temperature oxygen sorbent, YBaCo4O7+δ (YBC114), was investigated as an oxygen pumping material to facilitate solar thermochemical fuel production. The oxygen uptake and release attributes of YBC114 were studied by both TGA and a small-scale evacuation test. The study proved that the particle size has a significant effect on the oxygen pumping behavior of YBC114, especially for the uptake kinetics. / Dissertation/Thesis / Doctoral Dissertation Chemical Engineering 2020

Most of the coal properties depend on carbon content and vitrinite reflectance, which are rank dependent parameters. In this study, a new approach was followed by constructing a simulation input database with rank-dependent coal properties published in the literature which are namely cleat spacing, coal porosity, density, and parameters related to strength of coal, shrinkage, swelling, and sorption. Simulations related to enhanced coalbed methane (ECBM) recovery, which is the displacement of adsorbed CH4 in coal matrix with CO2 or CO2/N2 gas injection, were run with respect to different coal properties, operational parameters, shrinkage and swelling effects by using a compositional reservoir simulator of CMG (Computer Modeling Group) /GEM module. Sorption-controlled behavior of coalbeds and interaction of coal media with injected gas mixture, which is called shrinkage and swelling, alter the coal properties controlling gas flow with respect to injection time. Multicomponent shrinkage and swelling effects were modeled with extended Palmer and Mansoori equation. In conclusion, medium-volatile bituminous coal rank, dry coal reservoir type, inverted 5-spot pattern, 100 acre drainage area, cleat permeability from 10 to 25 md, CO2/N2 molar composition between 50/50 % and 75/25 %, and drilling horizontal wells rather than vertical ones are better selections for ECBM recovery. In addition, low-rank coals and dry coal reservoirs are affected more negatively by shrinkage and swelling. Mixing CO2 with N2 prior to its injection leads to a reduction in swelling effect. It has been understood that elastic modulus is the most important parameter controlling shrinkage and swelling with a sensitivity analysis.

A better understanding of the brine-rock- supercritical CO2 interaction is needed to evaluate the risks of geologic CO2 sequestration. The geochemical effects of brine and supercritical CO2 were examined via laboratory modeling of in situ conditions on two reservoir caprocks in the Black Warrior River Basin, the Pottsville and Parkwood Formations. The clay fraction was extracted and treated at ~ 100 bar and 363 K (90 °C) over periods of up to 70 hours. Supercritical CO2 was introduced as dry ice in a pressurized vessel. Samples were observed using XRD, WD-XRF, AA, SEM, and EDS. Clay fractions contained Fe-chlorite, illite, kaolinite, and quartz. Results show the dissolution of illite, CO2-brine induced cation exchange ok K+, and the dissolution of silicate minerals. Steady-state K/Si ratios in the fluid suggest quartz re-precipitation. These interactions could adversely affect the long-term storativity of the caprock and point to a need for further study.

Le stockage géologique du CO2 dans des réservoirs aquifères de type calcaire et grès, du charbon non exploité est une des solutions envisagées pour réduire les émissions de gaz à effet de serre dans l’atmosphère. Cependant, l’injection de CO2 peut perturber les propriétés pétrophysiques (porosité et perméabilité), minéralogiques (transformations) et mécaniques (déformations, résistance à la rupture) des roches réservoir (calcaire, grès, charbon). Dans le cas du charbon, l’injection de CO2 peut également se traduire par des phénomènes de gonflement de la matrice liés au processus d’adsorption. L’objectif de ce travail de thèse est de traduire en termes de modèles phénoménologiques les comportements et les couplages chimio-poromécaniques des roches réservoir de type charbon. Dans ce travail, nous nous sommes focalisés en particulier sur l’étude de l’injection de CO2 dans le charbon. Pour cela, deux modèles homogénéisés de porosité du charbon ont été développés avec la prise en compte du phénomène d’adsorption, connu pour être le principal mécanisme de production ou de séquestration de CO2 dans de nombreux réservoir de charbon. Le premier modèle permet d’étudier le comportement poro-élastique du charbon pour une injection simple de CO2 et le second permet d’étudier le comportement poro-élastique du charbon pour une injection de CO2 avec une récupération assistée de méthane CH4. Le processus d’adsorption est classiquement modélisé à l’aide de l’isotherme d’adsorption de Langmuir (pour un gaz dans le premier modèle et pour deux gaz dans le second modèle). L’implantation de ces modèles dans le Code_Aster (code d’analyse de calcul de structures entièrement couplé THM, développé par Electricité De France - EDF) nous a permis de faire des simulations numériques de stockage de CO2 dans le charbon. Pour une injection simple du CO2 dans le charbon (premier modèle), la matrice du charbon s’est comportée de deux façons différentes : elle gonfle (ce qui induit une diminution de la porosité du charbon) avec la prise en compte du phénomène d’adsorption et se contracte (ce qui induit une augmentation de la porosité du charbon) dans le cas contraire. Etant en bon accord avec les résultats de la littérature spécialisée, cela montre la capacité du modèle à prédire le comportement poro-élastique du charbon durant l’injection de CO2. Toujours avec le premier modèle, nous avons en particulier étudié l’influence des propriétés hydro-mécaniques du charbon (coefficient de Biot, module de Young/module d’incompressibilité), les paramètres d’adsorption de Langmuir et la pression initiale du liquide interstitiel dans le charbon, sur la réponse du charbon à l’injection du CO2. Dans le cas d’une récupération assistée du méthane CH4 (le second modèle), un couplage du Code_Aster et un code de transport réactif HYTEC (HYdrological Transport coupled with Equilibrium Chemistry, développé par MINES Paris Tech) était nécessaire pour gérer surtout le calcul des pressions partielles des deux gaz (CO2 et CH4) à chaque pas de temps. Un travail de développement numérique sur les deux codes de calcul était alors nécessaire. Ce travail de thèse a proposé une méthode de couplage entre les deux codes (Code_Aster et HYTEC) dont les techniques sont largement décrites dans le manuscrit. / The geological storage of CO2 in aquifers reservoirs such as limestone and sandstone, coal is a possible way to reduce greenhouse gas emission into the atmosphere. However, the injection of CO2 may modify petrophysical (porosity and permeability), mineralogical (transformations) and mechanical (deformations, strength) properties of reservoir rocks (limestone, sandstone, coal). In the case of coal, the injection of CO2 can also induce matrix swelling due to adsorption processes. The focus of this thesis is to translate in terms of phenomenological models, the behaviors and chemo-poromechanical coupling of reservoir rocks of coal type. In this work, we focused particularly on the study of CO2 injection into coal. For this, two models of homogenized coal porosity have been developed by taking into account the adsorption phenomenon, known to be the main mechanism of production or sequestration of CO2 in many coal reservoirs. The first model allows the study of the poroelastic behavior of coal in the case of a single injection of CO2, and the second model allows the study of the poroelastic behavior of coal in the case of an injection of CO2 with methane CH4 recovery. The adsorption process is classically modelled using Langmuir’s isotherm (for one gas in the first model and for two gases in the second model). The implementation of these models in Code_Aster (a fully coupled Thermo-Hydro-Mechanical analysis code for structures calculations, developed by Electricity of France - EDF) allowed us to make numerical simulations of CO2 storage in coal. For a single injection of CO2 into coal (first model), the coal matrix behaved in two different ways: it swells (resulting in the decrease of coal porosity) when the adsorption phenomenon is taken into account and shrinks (resulting in the increase of coal porosity) otherwise. Being in good agreement with the results in specialized literature in this field, it shows the ability of the model to predict the poroelastic behaviour of coal to CO2 injection. Also with the first model, we studied particularly through numerical simulations the influence of coal’s hydro-mechanical properties (Biot’s coefficient, bulk modulus), Langmuir’s adsorption parameters and the initial liquid pressure in rock mass during CO2 injection in coal. In the case of methane recovery (second model), a coupling of Code_Aster and a reactive transport code, HYTEC (Hydrological Transport coupled with Equilibrium Chemistry, developed by Mines Paris Tech) was needed to handle the above calculation of partial pressures of the two gases (CO2 and CH4) at each time step. Digital development work on the two computers codes (Code_Aster and HYTEC) was then necessary. This thesis proposed a method of coupling between the two codes whose techniques are widely described in the manuscript.