Geological Carbon Dioxide Research Articles

Dissolution-driven convection in a Hele–Shaw cell

Motivated by convection in the context of geological carbon-dioxide (CO2) storage, we present an experimental study of dissolution-driven convection in a Hele–Shaw cell for Rayleigh numbers \documentclass[12pt]{minimal}\begin{document}$\mathcal {R}$\end{document}R in the range \documentclass[12pt]{minimal}\begin{document}$100 < \mathcal {R}< 1700$\end{document}100<R<1700. We use potassium permanganate (KMnO4) in water as an analog for CO2 in brine and infer concentration profiles at high spatial and temporal resolution and accuracy from transmitted light intensity. We describe behavior from first contact up to 65% average saturation and measure several global quantities including dissolution flux, average concentration, amplitude of perturbations away from pure one-dimensional diffusion, and horizontally averaged concentration profiles. We show that the flow evolves successively through distinct regimes starting with a simple one-dimensional diffusional profile. This is followed by linear growth in which fingers are initiated and grow quasi-exponentially, independently of one-another. Once the fingers are well-established, a flux-growth regime begins as fresh fluid is brought to the interface and contaminated fluid removed, with the flux growing to a local maximum. During this regime, fingers still propagate independently. However, beyond the flux maximum, fingers begin to interact and zip together from the root down in a merging regime. Several generations of merging occur before only persistent primary fingers remain. Beyond this, the reinitiation regime begins with new fingers created between primary existing ones before merging into them. Through appropriate scaling, we show that the regimes are universal and independent of layer thickness (equivalently \documentclass[12pt]{minimal}\begin{document}$\mathcal {R}$\end{document}R) until the fingers hit the bottom. At this time, progression through these regimes is interrupted and the flow transitions to a saturating regime. In this final regime, the flux gradually decays in a manner well described by a Howard-style phenomenological model.

Depositional Environment as an Indicator of Favorable Regional Sequestration Targets: Examples from the USGS CO2 Storage Resource Assessment

An analysis of the of sealing formations chosen as cap rocks in the U.S. Geological Survey (USGS) geologic carbon dioxide (CO2) storage resource assessment reveals certain depositional environments that produce suitable regional scale sequestration seals. The USGS methodology requires low permeability, regional, and homogenous seals of approximately 30 meters thickness for shales and 6 meters thickness for evaporites. Open-shelf marine slope and basin shales, as well as shallow water evaporitic deposits make up a majority of storage formation seals identified in the assessment that meet this criteria. Since adequate cap rock is the limiting component of the reservoir and seal couplet required to sequester CO2, these specific depositional environments are recommended as initial targets for regional-scale sequestration assessments and research.

Dissipation of Overpressure into Ambient Mudrocks During Geological Carbon Dioxide Storage

Geological carbon dioxide (CO2) storage in deep geological formations can only lead to significant reductions in anthropogenic CO2 emissions if large amounts of CO2 can be stored. Estimates of the storage capacity are therefore essential to the evaluation of individual storage sites as well as the feasibility of the technology as a whole. One important limitation on the storage capacity is the lateral extent of the pressure perturbation, the radius of review of the storage project. We show that pressure dissipation into ambient mudrocks retards lateral pressure propagation significantly and therefore increases the storage capacity. For a three-layer model of an aquifer surrounded by thick mudrocks the far-field pressure is well approximated by a single-phase model. Through dimensional analysis and numerical simulations we show that the lateral pressure propagation follows a power-law that depends on a single parameter M ∼ log10(RkRSR12), where Rk and RS are the ratios of mudrock to reservoir permeability and storativity and Rl is the aspect ratio of the confined pressure plume. Both the coefficient and the exponent of the power-law are sigmoid decreasing functions of M. The M-values of typical geological storage sites are in the region where the power-law is changing rapidly. The combinations of large uncertainty in mudrock properties and the sigmoid shape lead to wide and strongly skewed probability distributions for the predicted radius of review. Therefore, the determination of the mudrock properties is an important component of the site characterization, if pressure dissipation has the potential significantly increase storage capacity. After injection the pressure will continue to diffuse and the radius of review may continue to increase, which will emphasize the significance of monitoring post-injection overpressure to secure the stability of the storage formation.

PVTX Properties of H2O-CO2-"salt" at PTX Conditions Applicable to Carbon Sequestration in Saline Formations

Among the many scenarios that have been proposed to reduce the amount of carbon dioxide (CO2) emissions to the atmosphere, carbon-capture and storage (CCS) in geological reservoirs represents the method most technologically feasible and capable of accommodating the large amounts of CO2 that are generated on an annual basis by combustion of fossil fuels (IPCC, 2005). Geological environments and processes that have been proposed for CCS include deep, unmineable coal seams, depleted oil and gas reservoirs, organic-rich shale basins, deep saline formations, and mineral carbonation of basalts. Of these various options, the one that is most attractive owing to its widespread distribution and capacity to store large amounts of CO2 is deep saline formations, with the U.S. Department of Energy reporting that saline formations in the United States could potentially store more than 2,100–20,000 billion metric tons of CO2 (DOE, 2012). A recently released assessment of geologic carbon dioxide storage potential (USGS, 2013) estimates a capacity ranging from 2,400 to 3,700 billion metric tonnes (Gt) of CO2, which corresponds to the low end of the DOE estimate. When supercritical CO2 (scCO2) is injected into a saline formation, it may be stored in various ways. Initially, the CO2 will be stored by structural and stratigraphic trapping, whereby scCO2 is trapped beneath an impermeable confining layer that prohibits the upward migration of the more buoyant scCO2. Some scCO2 may also be stored by residual trapping in pores via capillary forces. In the discussion to follow, we include residual trapping with structural/stratigraphic trapping as all of these processes involve the storage of a scCO2 phase and, as such, the volume requirements are assumed to be identical for these storage mechanisms for a given mass of CO2. Over time, …

High-performance Supercomputing as a Risk Evaluation Tool for Geologic Carbon Dioxide Storage

Numerical modelling is a vital tool for predicting the behavior and fate of CO2 in reservoirs as well as its impacts on subsurface environments. Recently, powerful numerical codes that are capable of solving coupled complex processes of physics and chemistry required for such modeling works have been developed. However they are often computationally demanding for solving the complex non-linear models in sufficient spatial and temporal resolutions. Geological heterogeneity and uncertainties further increase the challenges in modeling work, because they may necessitate stochastic modeling with multiple realizations. There is clearly a need for high-performance computing. In this study, we implemented TOUGH2-MP code (a parallel version of multi-phase flow simulator TOUGH2) on two different types (vector- and scalar-type) of world-class supercomputers with tens of thousands of processors in Japan. The parallelized code generally exhibited excellent performance and scalability after adequate tune-ups of the code. Using the code and the supercomputers, we have been performed several computationally demanding simulations. In this paper, we present the performances of parallel computation of the code measured on the two supercomputers. Then the following two examples are presented: 1) a highly heterogeneous high-resolution model, representing irregular nature of sand/shale distribution; 2) “Dissolution Diffusion Convection Process”, which is expected to significantly enhance the dissolution trapping. Through the above two examples, it is illustrated that the spatial resolution of numerical model can critically change the evaluation of the effectiveness of CO2 trapping mechanisms, demonstrating the necessity of supercomputing techniques for evaluating these risks more accurately.

Correlation Analysis for Online CO2 Leakage Monitoring in Geological Sequestration

The paper presents a method for monitoring CO2 leakage in geological carbon dioxide sequestration. The unsteady state dispersion of leakage CO2 from geosequestration simulation results showed that the ensemble trend of elevated concentration caused by CO2 leakage can be viewed as a concentration step change perturbation to the background variation and the initial stage of dispersion process is an increasing variation. The correlation between O2 and CO2 variation is well linear if there is no leakage. The external linear perturbation decreases the correlation coefficient. Moreover, too large step change concentration will also reduce the average correlation coefficient. Therefore, online correlation analysis between O2 and CO2 in atmosphere is useful to distinguish the leakage CO2 from complex background variation especially at the beginning of leakage occurring.

CO2 Sequestration Potential of Unmineable Coal—State of Knowledge

Currently the U.S. Geological Survey (USGS) national assessment of geological carbon dioxide (CO2) storage resource considers porous sandstones, limestones, and dolomites as potential storage formations. Assessment of an additional potential geologic storage resource within unmineable coal seams was deferred because no consensus exists on what constitutes unmineable coal. Because unmineable coal seams may be considered potential storage resources in future assessments, however, the USGS is researching factors affecting CO2 storage potential in coal.

Reducing Uncertainty in Reservoir Model Predictions: from Plume Evolution to Tool Responses

With the transition of geological carbon dioxide (CO2) storage from pilot to industrial scale, risk analysis has become pivotal for assessing the suitability of a storage site in satisfying regulatory requirements during and after injection. Risk analysis is inherently related to uncertainty quantification. This paper extends our previously developed workflows to quantify and propagate uncertainty from geological, geophysical and petrophysical data to project-level performance metrics including capacity, injectivity, and containment characteristics. We perform global sensitivity analysis to quantitatively link uncertainty in the computed performance metrics to the uncertainties in the underlying reservoir parameters. This enables one to identify measurements to reduce uncertainty estimates of reservoir performance metrics and predicted monitoring tool responses. We illustrate this workflow in a pre-injection uncertainty study for the Illinois Basin Decatur Project (IBDP). The reservoir model is built using geostatistical approach based on all available geophysical and petrophysical data including 3D seismic interpretation, results of special core analysis and injectivity tests. We focus on three groups of performance predictions: spatial extent of the CO2 saturation profile, partitioning of CO2, and predicted responses seen with the Westbay* multilevel groundwater characterization and monitoring system installed in the monitoring well. Based on multiple realizations of the reservoir model we evaluate the uncertainty range in pressures and CO2 saturations at the Westbay monitoring zones during the life of the project. Predicted measurements at the monitoring zones covering a depth interval between 1950 m and 2120 m are analyzed. Global sensitivity analysis is used to identify the key petrophysical properties of the reservoir whose uncertainties have the most effect on the uncertainty of the reservoir performance and measurement predictions. Results of this analysis provide valuable insight for targeted site characterization and design of the monitoring program.

U.S. Geological Survey Geologic Carbon Dioxide Storage Resource Assessment of the United States

The U.S. Geological Survey (USGS) is conducting geology-based carbon dioxide storage resource evaluations of approximately 40 major sedimentary basins in the United States in order to fulfill some of the requirements of the Energy Independence and Security Act of 2007. Individual storage assessment units (SAUs) within each basin are defined on the basis of geologic and hydrologic characteristics. Summary geologic descriptions of the evaluated basins and SAUs will be published, along with the results of the national assessment and related research.

Safety-based Injection Strategy for Carbon Dioxide Geological Sequestration in a Deep Saline Aquifer with Complex Sandstone-shale Sequences: A Case Study from Taiwan

The purpose of this study was to decide the best injection strategy for CO2 geo-sequestration in a deep saline aquifer with complex bedded sandstone-shale sequences. The best injection strategy is decided based on the estimates of the safety index (SFI). Numerical simulation method was used in this study. The major conclusions from this study are: (1) Safe trapping mechanisms contribute to a lower risk of CO2 leakage by trapping CO2 as immobile blobs or changing the phase of CO2 from supercritical phase to aqueous, ionic, and mineral phases in the post-injection period. (2) For an aquifer with complex sandstone-shale sequences, the best injection strategy should be decided by the results of risk evaluation and the SFI estimation. (3) The well location affected the injection strategy. The risk of CO2 leakage was lower using a down-dip injection well than an up-dip well. (4) The best strategy for this case study was to use the down-dip well to inject CO2 into the bottom sandstone layer. The SFI for this scenario reached 0.99 at the storage time of 1000 years, which meant that the probability of CO2 leakage occurring was nearly zero.

Microfracturation in rocks: from microtomography images to processes

EDP Sciences 2012Abstract. Fracturing of rocks and other geomaterials involves multi-scale processes, from the nucleationof small cracks, their propagation into a complex heterogeneous solid, to their final arrest. In the past10 years, advances in X-ray tomography imaging techniques, either three dimensional or four dimensionalwhen time-lapse acquisitions are performed, allow detecting fractures at small scale and the growth andcoalescence of tiny cracks into well-developed fractures. Some of these fracturing processes involve thecoupling between fluids, chemical reactions and fracturing. In the present study I illustrate some of theseprocesses, how they can be imaged using high-resolution X-ray computed tomography; and how conceptualmodels can make the link between microscopic processes and macroscopic fracturing. This concerns a widerange of applications in geophysics, from fundamental understanding of the rheology of rocks in the Earth’scrust, to salt damage of cultural heritage monuments, hydraulic fracturing of underground reservoirs oremerging technologies of non-conventional hydrocarbon recovery and the underground geological storageof carbon dioxide.

Ganglion Dynamics and Its Implications to Geologic Carbon Dioxide Storage

Capillary trapping of a nonwetting fluid phase in the subsurface has been considered as an important mechanism for geologic storage of carbon dioxide (CO(2)). This mechanism can potentially relax stringent requirements for the integrity of cap rocks for CO(2) storage and therefore can significantly enhance storage capacity and security. We here apply ganglion dynamics to understand the capillary trapping of supercritical CO(2) (scCO(2)) under relevant reservoir conditions. We show that, by breaking the injected scCO(2) into small disconnected ganglia, the efficiency of capillary trapping can be greatly enhanced, because the mobility of a ganglion is inversely dependent on its size. Supercritical CO(2) ganglia can be engineered by promoting CO(2)-water interface instability during immiscible displacement, and their size distribution can be controlled by injection mode (e.g., water-alternating-gas) and rate. We also show that a large mobile ganglion can potentially break into smaller ganglia due to CO(2)-brine interface instability during buoyant rise, thus becoming less mobile. The mobility of scCO(2) in the subsurface is therefore self-limited. Vertical structural heterogeneity within a reservoir can inhibit the buoyant rise of scCO(2) ganglia. The dynamics of scCO(2) ganglia described here provides a new perspective for the security and monitoring of subsurface CO(2) storage.

Combining geothermal energy capture with geologic carbon dioxide sequestration

[1] Geothermal energy offers clean, renewable, reliable electric power with no need for grid-scale energy storage, yet its use has been constrained to the few locations worldwide with naturally high geothermal heat resources and groundwater availability. We present a novel approach with the potential to permit expansion of geothermal energy utilization: heat extraction from naturally porous, permeable formations with CO2 as the injected subsurface working fluid. Fluid-mechanical simulations reveal that the significantly higher mobility of CO2, compared to water, at the temperature/pressure conditions of interest makes CO2 an attractive heat exchange fluid. We show numerically that, compared to conventional water-based and engineered geothermal systems, the proposed approach provides up to factors of 2.9 and 5.0, respectively, higher geothermal heat energy extraction rates. Consequently, more regions worldwide could be economically used for geothermal electricity production. Furthermore, as the injected CO2 is eventually geologically sequestered, such power plants would have negative carbon footprints.

The critical role of monitoring, verification, and accounting for geologic carbon dioxide storage projects

A growing concern that increasing levels of greenhouse gases in the atmosphere are contributing to global climate change has led to a search for economical and environmentally sound ways to reduce carbon dioxide (CO2) emissions. One promising approach is CO2 capture and permanent storage in deep geologic formations, such as depleted oil and gas reservoirs, unminable coal seams, and deep brine-containing (saline) formations. However, successful implementation of geologic storage projects will require robust monitoring, verification, and accounting (MVA) tools. This article deals with all aspects of MVA activities associated with such geologic CO2 storage projects, including site characterization, CO2 plume tracking, CO2 flow rate and injection pressure monitoring, leak detection, cap-rock integrity analysis, and long-term postinjection monitoring. Improved detailed decision tree diagrams are presented covering the five stages of a geologic storage project. These diagrams provide guidance from the point of site selection through construction and operations to closure and postclosure monitoring. Monitoring, verification, and accounting techniques (both well-established and promising new developments) appropriate for various project stages are discussed. Accomplishments of the Department of Energy (DOE) Regional Carbon Sequestration Partnerships field projects serve as examples of the development and application to geologic storage of MVA tools, such as two-dimensional and three-dimensional seismic and microseismic, as well as the testing of new cost-effective monitoring technologies. Although it is important that MVA and computer simulation efforts be carefully integrated to ensure long-term success of geologic storage projects, this article is limited to a discussion of MVA activities. This article is an extension of a report published in 2009 by the DOE National Energy Technology Laboratory titled, “Best Practices for Monitoring, Verification, and Accounting of CO2 Stored in Deep Geologic Formations,” to which interested readers are referred for more details on MVA tools. Ultimately, a robust MVA program will be critical for establishing carbon capture and storage as a viable greenhouse gas mitigation strategy.

Carbon dioxide storage potential for the Queenston Formation near the AES Cayuga coal-fired power plant in Tompkins County, New York

We evaluated the pore volume available for a specific potential geologic carbon dioxide (CO2) storage site in the Upper Ordovician Queenston Formation near the AES Corporation Cayuga coal-fired power plant in Tompkins County, New York. Core data collected 25 mi (40 km) from the plant reveal that the Queenston Formation is a relatively homogeneous fine- to medium-grained sandstone with hematite cement. Seismic and core data indicate that the formation was deposited in a fluvial system with mobile channels and has thickness maxima that trend north-northwest. Porosity is a major factor affecting geologic CO2 storage potential, and it is important to understand discrepancies among porosity measured from core plug, neutron porosity, density-derived porosity, and thin-section point count values. Relative to core plug–derived porosity values, the neutron porosity log is more reliable than the electron density porosity values. Thin sections reveal that hematite cement is the primary factor affecting porosity variability. Seismic, core, and well-log data suggest that in a 25-mi2 (65-km2) area surrounding this power plant, the Queenston Formation can sequester 18 million metric tons (11 million metric tons) of CO2 emission from the Cayuga power plant (8 yr of CO2 output, with a range of 3–12 yr), although many uncertainties must be better constrained to obtain a more accurate estimate. Because the Queenston Formation near the Cayuga power plant is relatively homogeneous, most of the formation at this location offers the potential for CO2 storage in its pore space.

Bacterially Acceleration of Caco 3 Mineralization

Geologic carbon dioxide sequestration, the underground storage of carbon dioxide, will be an essential component of climate change mitigation. Carbonate minerals are a promising form of stable CO2 storage, but their natural formation is slow. Many microbes can influence the precipitation of carbonate minerals; however the mechanisms of such mineralization are largely unknown. Hypothesized mechanisms include metabolic processes altering pH and supersaturation, as well as cell surface properties of extracellular polymeric substances (EPS), cell membrane, and protein surface layers (S-layers) that may alter mineral nucleation. This work investigates these mechanisms by allowing calcium carbonate (CaCO3) to form in microbial solutions of Escherichia coli (E. coli) or Synechocystis sp. PCC 6803 (Syn. sp. 6803) with varying calcium ion concentrations, via the ammonium carbonate diffusion method. The resulting CaCO3 was imaged with an optical microscope in tandem with fluorescent imaging of the bacteria. Surprisingly, formation of CaCO3 was accelerated in the presence of either species. This rate acceleration also occurred for metabolically inactive bacteria, suggesting metabolic change was not the operating mechanism. Calcium carbonate crystals increased in number as cell density increased. Fluorescent images show that both species of bacteria cluster on the edges and crevices of the crystals, further supporting this idea. Bacterial surface charge was assessed using zeta potential measurements and correlated to biomineralization experiments. From these results, we postulate that the charged bacterial surfaces attract Ca2+ ions, serving as nucleation sites for CaCO3, thereby accelerating crystal formation. These observations provide substantive evidence for a non-specific nucleation mechanism, and stress the importance of microbes, even dead ones, on the rate of formation of carbonate minerals. This work also indicates that additional microbial engineering could optimize these interactions and be used to implement the sequestration of CO2 as stable mineral carbonates on an accelerated timescale. http://foundry.lbl.gov/afgroup/index.html

Case study of the cementing phase of an observation well at the Pembina Cardium CO2 monitoring pilot, Alberta, Canada

The Pembina field was chosen from several fields within Alberta, Canada, for a geological carbon dioxide (CO2) storage pilot study, in which the injection of CO2 was combined with enhanced oil recovery (EOR). As part of the project, an existing wellbore within the study area was used as a dedicated observation well. The design and initial results during cementing of this observation well are reviewed. The experience of implementing monitoring technologies was analyzed in order to assess existing knowledge for deploying downhole instrumentation used for monitoring and verification of CO2 movements in the subsurface. Analysis indicates that the observation well allows direct monitoring and measurements at reservoir level of multiple variables through geophysical, geochemical, and geomechanical instrumentation, as well as the opportunity to carry out wellbore integrity studies under in situ conditions. A post-cement job and completion analysis that couples downhole measurements and analytical simulation was conducted to improve future installations. Results verified that equivalent circulation density profiles, and minimum and maximum flow rates during placement should be determined prior cementing operations to avoid influx or fracturing in pre-cased observation wells. Results also indicate that pressure signatures during cement circulation are dominated by fluid density, volume, and rate, and not by sensor assemble geometries used to diagnose the operation. Downhole pressure gauges captured the dynamics of cement displacement and were key elements during post-cement job review and assessments of future well integrity. The experience and analyses gained from the installation of this observation well provide valuable insight for CO2 geological storage monitoring and risk/performance assessment.

Regulatory framework for geological storage of CO2 in Brazil – Analyses and proposal

The lack of specific regulation for new technologies such as Carbon Dioxide Geological Storage (CGS) represents an obstacle in the fight against global warming and its consequences. Carbon dioxide is a greenhouse gas and a reduction in its concentration in the atmosphere through geological storage has been highlighted as an important initiative. As this is a little researched technology there is a lack of specific regulation to accompany its large scale usage. However, some developed countries have already structured their CGS regulatory framework. According to international studies one basic aspect in building a CGS regulatory structure lies in its correlation with natural gas and oil regulation. This article presents a regulatory framework Brazilian CGS proposal and suggests the creation of a new law on the subject and the development of its main regulatory mechanisms. The methodology used in this article is based on a review of literature and comparative analysis. A survey of the existing Brazilian legal framework on oil and gas was made. Focusing on the critical points of a Brazilian regulatory framework for CGS proposal this article identifies several technical, legal and structural aspects that must be present in the regulation.

Road-testing the outreach best practices manual: Applicability for implementation of the development phase projects by the regional carbon sequestration partnerships

Abstract Geologic carbon dioxide (CO 2 ) storage verification tests by the U.S. Department of Energy’s (DOE’s) seven Regional Carbon Sequestration Partnerships (RCSPs) provided the experience base for the Public Outreach and Education for Carbon Storage Projects, a best practices manual, published in December 2009. This paper summarizes these outreach best practices; discusses their application in Aquistore, a greenfield CO 2 storage project under way in western Canada; and reviews the implications for applying the best practices to new projects during the Development Phase of the DOE’s RCSP Program.

Applying underground gas storage experience to geological carbon dioxide storage: A case study from Australia’s Otway Basin

Abstract Underground gas storage (UGS) facilities provide a wealth of information, which can be used to better understand various aspects of CO2 storage in depleted reservoirs. In some cases UGS facilities can provide important site specific information for carbon storage projects that are planned in similar formations in close proximity. In this paper, we discuss the various ways in which UGS facilities can be used to extract important information, and when possible we draw upon information from the Iona gas storage facility in Australia’s Otway basin. The Iona facility is located 20 km away from the CO2CRC Otway Project, in which CO2 65445 tonnes of 77 mole% carbon dioxide, 20 mole% methane and 3 mole% other gas components (containing about 58000 tonnes of carbon dioxide) was injected into the Waarre C formation over a 17 month period. In this paper, we compare the factors that control CO2 seal capacity and discuss how UGS facilities can provide information on sustainable column heights either limited by faults or by cap rocks. We also present dynamic modeling results in which information is gained regarding injectivity, pressure evolution of the reservoir, storage capacity and maximum fluid pressures sustained by the faults. Understanding such parameters is important for the safe operation of any carbon storage project, be it on a demonstration or industrial scale.