CO2 In Deep Aquifers Research Articles

A parallel compositional reservoir simulator for large-scale CO2 geological storage modeling and assessment

Storing CO2 in deep aquifers and depleted gas reservoirs is an effective way to achieve carbon neutrality. However, the numerical simulation of CO2 storage in these formations is challenging due to the complexity of gases-brine systems. The number of gas species included in the gases-brine fluid models of existing simulators cannot meet the rapidly evolving CO2 sequestration scenarios. To address this intricate issue, we developed a three-dimensional fully implicit parallel CO2 geological storage simulator (PRSI-CGCS) on distributed-memory computers based on our in-house parallel platform. This simulator uses a compositional fluid model with a diverse range of gas species, including CO2, C1 ~ C3, N2, H2S, as well as newly added gases H2 and O2, which may be encountered in geological CO2 storages. Besides, we provide more suitable scaling factors for different gases in the stability analysis bypassing (SAB) method to accelerate the gases-brine phase equilibrium calculations. PRSI-CGCS does not incorporate energy conservation equations, and salt precipitation or dissolution is also not considered. Numerical experiments show that our simulator is scalable, robust and validated to simulate large-scale CO2 storage problems with hundreds of millions of grid blocks on a parallel supercomputer cluster. Besides, after our modification on scaling factors, the SAB method can reduce the number of stability analyses by 61.39 % to 88.71 %, thereby reducing simulation time. Furthermore, case studies indicate that injecting O2 and H2 along with CO2 reduces the stability or capacity of CO2 storage and increases the pressure required for injection. However, this impact is not significant when the impurity content is less than 10 %.

Sources and concentrations of methane, ethane, and CO2 in deep aquifers of the Surat Basin, Great Artesian Basin

Understanding the occurrence and sources of methane in aquifers is an international issue, especially in regions that host oil and gas reservoirs. Multi-isotopic studies are important to understand sources and concentrations of dissolved gases in aquifers of basins that host oil and gas extraction; or future CO2, natural gas, hydrogen storage, or compressed air energy storage. The largest artesian basin in the world, the Great Artesian Basin, extends across more than one fifth of Australia providing a fresh water source from various aquifers. The Precipice and Hutton sandstones, aquifers of the Surat Basin in the eastern Great Artesian Basin, are important water resources for town water supply, agriculture, mines, feedlots, and private landholders in Queensland. Overlying and underlying formations host gas extraction. The southern part of the basin in Queensland additionally hosts an oil field, and potential CO2 storage sites, therefore understanding the aquifer gas concentrations, processes and sources is important for fluid management. The dissolved concentrations of methane and ethane in the Hutton Sandstone were up to 96 mg/L and 1 mg/L respectively, and in the Precipice Sandstone methane ranged up to 2100 mg/L and ethane 6.5 mg/L in the southern Surat Basin. Dissolved gas concentrations were measured by an open and closed sampling method, with the concentrations lower from open sampling, and the gas wetness parameter systematically slightly lower. The Hutton Sandstone aquifer dissolved gas isotopic signatures are mainly consistent with primary microbial CO2 reduction generating methane in situ, with fractionation factors indicating acetate fermentation in a few cases. The Hutton Sandstone δ13C-DIC, δ13C-CO2, and δ13C-CH4 have an enrichment trend with increasing depth that indicate a microbial substrate depletion effect. Moonie Oil Field Precipice Sandstone and Evergreen Formation samples plot in the thermogenic region, with enriched δ13C-CO2 indicating microbial biodegradation is also occurring. The Precipice Sandstone aquifer samples have a mixed microbial CO2 reduction and early mature thermogenic gas signature in both isotope cross plots and gas wetness diagrams, with a subset of sampled δ13C-C2H6 and isotope factors consistent with early mature thermogenic gas. A potential historic source of thermogenic gas is the underlying gas reservoir of the Bowen Basin. Large volumes of water are abstracted from these aquifers, hence dissolved gases may contribute to greenhouse gas emissions.

Sources and Concentrations of Methane, Ethane, and Co2 in Deep Aquifers of the Surat Basin, Great Artesian Basin

Sources and Concentrations of Methane, Ethane, and Co2 in Deep Aquifers of the Surat Basin, Great Artesian Basin

The emerging role of 4D synchrotron X-ray micro-tomography for climate and fossil energy studies: five experiments showing the present capabilities atbeamline 8.3.2 at the Advanced Light Source.

Continuous improvements at X-ray imaging beamlines at synchrotron light sources have made dynamic synchrotron X-ray micro-computed tomography (SXR-µCT) experiments more routinely available to users, with a rapid increase in demand given its tremendous potential in very diverse areas. In this work a survey of five different four-dimensional SXR-µCT experiments is presented, examining five different parameters linked to the evolution of the investigated system, and tackling problems in different areas in earth sciences. SXR-µCT is used to monitor the microstructural evolution of the investigated sample with the following variables: (i) high temperature, observing in situ oil shale pyrolysis; (ii) low temperature, replicating the generation of permafrost; (iii) high pressure, to study the invasion of supercritical CO2 in deep aquifers; (iv) uniaxial stress, to monitor the closure of a fracture filled with proppant, in shale; (v)reactive flow, to observe the evolution of the hydraulic properties in a porous rock subject to dissolution. For each of these examples, it is shown how dynamic SXR-µCT was able to provide new answers to questions related to climate and energy studies, highlighting the significant opportunities opened recently by thetechnique.

Parallel Numerical Reservoir Simulations of Nonisothermal Compositional Flow and Chemistry

Summary This paper describes an efficient numerical scheme for nonisothermal compositional flow coupled to chemistry. An iterative implicit-pressure/explicit-composition (IMPEC) method is applied to solve the flow problem using a volume-balance-convergence criterion. A backward-Euler mixed finite-element method (FEM) with lowest-order RT0 elements is applied to solve the pressure equation, and a component local mass-preserving explicit scheme is used to update concentrations. Chemical reactions are solved using explicit Runge-Kutta (RK) ordinary-differential-equation (ODE) integration schemes. A higher-order Godunov method and a backward-Euler mixed FEM are applied for thermal advection and conduction, respectively, in a time-split scheme. One of the major applications of the method is in the modeling of field-scale carbon dioxide (CO2) sequestration as an enhanced-oil-recovery (EOR) process or for containment in deep saline aquifers where chemical reactions and temperature variations may have an effect on the flow and transport of CO2. Leakage patterns when CO2 is injected near leaky abandoned wells, the displacement of methane from depleted gas reservoirs, and accurate modeling of geochemical reactions involving injected CO2 are other applications of interest. Results of a benchmark problem in multiphase flow with several hydrocarbon components in formations with highly heterogeneous permeability on very fine grids, as well as a large-scale parallel implementation of modeling CO2 sequestration, are presented to justify the practical use of the model. A parallel efficiency of approximately 80% was observed on up to 512 cores in the benchmark study. Results from a problem simulating injection of CO2 in deep aquifers including nonisothermal and chemical effects are also presented. The results indicate a good agreement of the solutions with published data, where available. Numerical modeling and simulation of CO2 sequestration plays a major role in future site selections and in designing storage facilities for effective CO2 containment. The main contribution of this paper lies in providing a parallel and efficient method of simulating challenging compositional flow problems, such as in the study of CO2 sequestration, as well as flow coupled to thermal and geochemical effects.

Archaeoglobus fulgidus and Thermotoga elfii, Thermophilic Isolates from Deep Geothermal Water of the Paris Basin

Thermophilic anaerobic microorganisms with the ability to reduce sulfur compounds (e.g., sulfate and/or thiosulfate) were isolated from water samples collected from about 2000 meters depth at in situ temperatures of 70°C in a geothermal well from the Paris Basin (France). Chemical and isotopic analyses show that microbial sulfate reduction occurred in the samples. Two strains were characterized by both DNA/DNA hybridization and 16S rRNA gene sequence analysis, which indicated that they are most closely related to Thermotoga elfii, a thiosulfate-reducing bacterium, and Archaeoglobus fulgidus, a sulfate- and thiosulfate-reducing archaeon. Besides thiosulfate reduction using H2 as energy source, both isolates are shown to be able to retrieve energy from H2/Fe(III), a metabolic capability of importance in a deep biosphere context. It is suggested that T. elfii and A. fulgidus could be used, either as pure culture or as a consortium, in future laboratory studies aiming at better understanding microbial iron (III) and sulfate/thiosulfate reduction, hydrogen production/consumption, as well as the effect of microorganisms on the evolution of CO2 in deep aquifers. The present work examines numerous culture conditions and demonstrates that in spite of similarities in phylogenetic/genetic characteristics and in growth conditions, there are significant phenotypic differences between the isolated archaeal strain and the type strain of A. fulgidus. These differences, evidenced by a proteomic study, should be taken into account and could be useful parameters to be studied in the deep aquifers by geomicrobiological laboratories.