Jonathan Ennis-King

CO2-H2O mixtures in the geological sequestration of CO2. I. Assessment and calculation of mutual solubilities from 12 to 100°C and up to 600 bar

Abstract Evaluating the feasibility of CO 2 geologic sequestration requires the use of pressure-temperature-composition ( P - T - X ) data for mixtures of CO 2 and H 2 O at moderate pressures and temperatures (typically below 500 bar and below 100°C). For this purpose, published experimental P - T - X data in this temperature and pressure range are reviewed. These data cover the two-phase region where a CO 2 -rich phase (generally gas) and an H 2 O-rich liquid coexist and are reported as the mutual solubilities of H 2 O and CO 2 in the two coexisting phases. For the most part, mutual solubilities reported from various sources are in good agreement. In this paper, a noniterative procedure is presented to calculate the composition of the compressed CO 2 and liquid H 2 O phases at equilibrium, based on equating chemical potentials and using the Redlich-Kwong equation of state to express departure from ideal behavior. The procedure is an extension of that used by King et al. (1992), covering a broader range of temperatures and experimental data than those authors, and is readily expandable to a nonideal liquid phase. The calculation method and formulation are kept as simple as possible to avoid degrading the performance of numerical models of water-CO 2 flows for which they are intended. The method is implemented in a computer routine, and inverse modeling is used to determine, simultaneously, (1) new Redlich-Kwong parameters for the CO 2 -H 2 O mixture, and (2) aqueous solubility constants for gaseous and liquid CO 2 as a function of temperature. In doing so, mutual solubilities of H 2 O from 15 to 100°C and CO 2 from 12 to 110°C and up to 600 bar are generally reproduced within a few percent of experimental values. Fugacity coefficients of pure CO 2 are reproduced mostly within one percent of published reference data.

Onset of convection in anisotropic porous media subject to a rapid change in boundary conditions

Previous studies of fluid convection in porous media have considered the onset of convection in isotropic systems and the steady convection in anisotropic systems. This paper bridges between these and develops new results for the onset of convection in anisotropic porous media subject to a rapid change in boundary conditions. These results are relevant to sedimentary formations where the average vertical permeability is some fraction γ of the average horizontal permeability. Linear and global stability analyses are used to define the critical time tc at which the instability occurs as a function of γ and the dimensionless Rayleigh-Darcy number Ra* for both thermal and solute-driven convection in an infinite horizontal slab. Numerical results and approximate analytical solutions are obtained for both a slab of finite thickness and the limit of large slab thickness. For a thick slab, the increase in tc as γ decreases is approximately given by (1+γ)4∕(16γ2). One important application is to the geological sto...

Safe storage and effective monitoring of CO2 in depleted gas fields

Carbon capture and storage (CCS) is vital to reduce CO2 emissions to the atmosphere, potentially providing 20% of the needed reductions in global emissions. Research and demonstration projects are important to increase scientific understanding of CCS, and making processes and results widely available helps to reduce public concerns, which may otherwise block this technology. The Otway Project has provided verification of the underlying science of CO2 storage in a depleted gas field, and shows that the support of all stakeholders can be earned and retained. Quantitative verification of long-term storage has been demonstrated. A direct measurement of storage efficiency has been made, confirming that CO2 storage in depleted gas fields can be safe and effective, and that these structures could store globally significant amounts of CO2.

Coupling of geochemical reactions and convective mixing in the long-term geological storage of carbon dioxide

Abstract The effect of coupling of geochemical reactions with convective mixing of dissolved carbon dioxide during geological storage is investigated by both analytical and numerical techniques. In the limit of fast reactions, scaling arguments and stability analysis show that the time for the onset of convection could be increased by up to an order of magnitude due to consumption of the dissolved carbon dioxide in mineralization. Numerical simulations are then used to investigate the effect of general reaction rates in two contrasting mineralogies, including overall dissolution and the distribution of ion and mineral concentrations.

THE SEARCH FOR SITES FOR GEOLOGICAL SEQUESTRATION OF CO2 IN AUSTRALIA: A PROGRESS REPORT ON GEODISC

The APCRC GEODISC research program has encountered many challenges looking for geological sequestration sites for CO2, but has also found some solutions. Challenges already faced have been in effectively searching databases, developing uniform terminology and evaluation methodology, establishing comparative quality assessment of Australia’s sequestration sites against each other and against those from overseas, improving our understanding of the injection and trapping properties of CO2 and predicting its effects on reservoirs/seals, and developing economic and reservoir models. Pilot research projects at the regional and site specific levels have been used to address these issues, as well as developing generic models, before building site specific models. Issues such as storage efficiency and the use of carbonates as CO2 sequesrationt reain challenges for the future. Preliminary conclusions reached from the regional study of Australia suggest that suitable deep saline formations will be widespread, have the largest sequestration volumes, and are likely to be the most economically attractive option currently available. In the future, some depleted oil and gas fields and enhanced coalbed methane production sites may also represent local high-volume options. It is considered unlikely that sequestration into voids/cavities or associated with enhanced oil recovery (EOR) will represent attractive options other than in exceptional circumstances. Despite these limitations, it is expected that many of Australia’s sedimentary basins will have excellent sequestration sites. The GEODISC program will provide an assessment of the critical factors required for success at each site. Several of the highest-ranking saline formations are currently undergoing site-specific study. Early indications are that the petrophysical data required for models of injection, migration, and trapping is of limited availability. Various methods are required to estimate the distribution and likely variability of these parameters across any site. These and other uncertainties in the distribution, quantity and quality of data required for predictive modelling necessitate an innovative and thorough approach to handling both risk and uncertainty. This will also be a challenge to be addressed during the GEODISC program. From the GEODISC work to date, it appears that it will be technically feasible to sequester large quantities of CO2 in geological formations in Australia for long periods of time. What is less clear is whether this can be done at a cost that would not impose an unreasonable economic burden on Australian industry. The future results for GEODISC will be highly relevant to answering this key question.

Code Intercomparison Builds Confidence in Numerical Models for Geologic Disposal of CO2

Publisher Summary Different kinds of subsurface reservoirs have been proposed for geologic disposal of greenhouse gases, including saline aquifers (brine formations), depleted or depleting oil and gas reservoirs, and coalbeds. Injection of greenhouse gases into such formations will give rise to complex coupled processes of fluid flow, mechanical and chemical changes, and heat transfer. Mathematical models and numerical simulation tools will play an important role in evaluating the feasibility of geologic disposal of CO 2 , and in designing and monitoring CO 2 disposal operations. The models must accurately represent the major physical and chemical processes induced by injection of CO 2 into potential disposal reservoirs, such as miscible and immiscible displacement, partitioning of CO 2 among different fluid phases, chemical reactions, thermal effects, and geomechanical changes from increased pore pressures. It is essential to test and evaluate numerical simulation codes to establish their ability to model these processes in a realistic and quantitative fashion. The code inter-comparison study reported in this chapter is a first step in this direction.

Residual Trapping Beneath Impermeable Barriers During Buoyant Migration of \(\mathrm{CO}_2\)

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Spatial grid correction for short-term numerical simulation results of carbon dioxide dissolution in saline aquifers

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