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1.
Injection of fluids into deep saline aquifers is practiced in several industrial activities, and is being considered as part of a possible mitigation strategy to reduce anthropogenic emissions of carbon dioxide into the atmosphere. Injection of CO2 into deep saline aquifers involves CO2 as a supercritical fluid that is less dense and less viscous than the resident formation water. These fluid properties lead to gravity override and possible viscous fingering. With relatively mild assumptions regarding fluid properties and displacement patterns, an analytical solution may be derived to describe the space–time evolution of the CO2 plume. The solution uses arguments of energy minimization, and reduces to a simple radial form of the Buckley–Leverett solution for conditions of viscous domination. In order to test the applicability of the analytical solution to the CO2 injection problem, we consider a wide range of subsurface conditions, characteristic of sedimentary basins around the world, that are expected to apply to possible CO2 injection scenarios. For comparison, we run numerical simulations with an industry standard simulator, and show that the new analytical solution matches a full numerical solution for the entire range of CO2 injection scenarios considered. The analytical solution provides a tool to estimate practical quantities associated with CO2 injection, including maximum spatial extent of a plume and the shape of the overriding less-dense CO2 front. 相似文献
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3.
Victor Vilarrasa Diogo Bolster Marco Dentz Sebastia Olivella Jesus Carrera 《Transport in Porous Media》2010,85(2):619-639
The injection of supercritical CO2 in deep saline aquifers leads to the formation of a CO2 plume that tends to float above the formation brine. As pressure builds up, CO2 properties, i.e. density and viscosity, can vary significantly. Current analytical solutions do not account for CO2 compressibility. In this article, we investigate numerically and analytically the effect of this variability on the position
of the interface between the CO2-rich phase and the formation brine. We introduce a correction to account for CO2 compressibility (density variations) and viscosity variations in current analytical solutions. We find that the error in
the interface position caused by neglecting CO2 compressibility is relatively small when viscous forces dominate. However, it can become significant when gravity forces
dominate, which is likely to occur at late times of injection. 相似文献
4.
Ruben Juanes Christopher W. MacMinn Michael L. Szulczewski 《Transport in Porous Media》2010,82(1):19-30
We study a sharp-interface mathematical model of CO2 migration in deep saline aquifers, which accounts for gravity override, capillary trapping, natural groundwater flow, and
the shape of the plume during the injection period. The model leads to a nonlinear advection–diffusion equation, where the
diffusive term is due to buoyancy forces, not physical diffusion. For the case of interest in geological CO2 storage, in which the mobility ratio is very unfavorable, the mathematical model can be simplified to a hyperbolic equation.
We present a complete analytical solution to the hyperbolic model. The main outcome is a closed-form expression that predicts
the ultimate footprint on the CO2 plume, and the time scale required for complete trapping. The capillary trapping coefficient and the mobility ratio between
CO2 and brine emerge as the key parameters in the assessment of CO2 storage in saline aquifers. Despite the many approximations, the model captures the essence of the flow dynamics and therefore
reflects proper dependencies on the mobility ratio and the capillary trapping coefficient, which are basin-specific. The expressions
derived here have applicability to capacity estimates by capillary trapping at the basin scale. 相似文献
5.
Geological storage of anthropogenic CO2 emissions in deep saline aquifers has recently received tremendous attention in the scientific literature. Injected buoyant
CO2 accumulates at the top part of the aquifer under a sealing cap rock. Potential buoyant movement of CO2 has caused some concern that the high-pressure CO2 could breach the seal rock. However, CO2 will diffuse into the brine underneath and generate a slightly denser fluid that may induce instability and convective mixing.
Onset times of instability and convective mixing performance depend on the physical properties of the rock and fluids, such
as permeability and density contrast. We present the novel idea of adding nanoparticles (NPs) to injected CO2 to increase density contrast between the CO2-rich brine and the underlying resident brine and, consequently, decrease onset time of instability and increase convective
mixing. The analyses show that 0.001 volume fraction of NPs added to the CO2 stream shortens onset time of mixing by approximately 80% and increases convective mixing by 50%. If it thus originally takes
5 years for the overlying CO2 to start convective mixing, by adding NPs, onset time of mixing reduces to 1 year, and after initiation of convective mixing,
mixing improves by 50%. A reduction of the CO2 leakage risk ensues. In addition to other metallic NPs, use of processed depleted uranium oxide (DU) as the NPs is also proposed.
DU-NPs are potentially stable and might be safely commingled with CO2 to store in saline aquifers. 相似文献
6.
Numerical Simulation Studies of the Long-term Evolution of a CO<Subscript>2</Subscript> Plume in a Saline Aquifer with a Sloping Caprock 总被引:1,自引:0,他引:1
We have used the TOUGH2-MP/ECO2N code to perform numerical simulation studies of the long-term behavior of CO2 stored in an aquifer with a sloping caprock. This problem is of great practical interest, and is very challenging due to
the importance of multi-scale processes. We find that the mechanism of plume advance is different from what is seen in a forced
immiscible displacement, such as gas injection into a water-saturated medium. Instead of pushing the water forward, the plume
advances because the vertical pressure gradients within the plume are smaller than hydrostatic, causing the groundwater column
to collapse ahead of the plume tip. Increased resistance to vertical flow of aqueous phase in anisotropic media leads to reduced
speed of up-dip plume advancement. Vertical equilibrium models that ignore effects of vertical flow will overpredict the speed
of plume advancement. The CO2 plume becomes thinner as it advances, but the speed of advancement remains constant over the entire simulation period of
up to 400 years, with migration distances of more than 80 km. Our simulations include dissolution of CO2 into the aqueous phase and associated density increase, and molecular diffusion. However, no convection develops in the aqueous
phase because it is suppressed by the relatively coarse (sub-) horizontal gridding required in a regional-scale model. A first
crude sub-grid-scale model was developed to represent convective enhancement of CO2 dissolution. This process is found to greatly reduce the thickness of the CO2 plume, but, for the parameters used in our simulations, does not affect the speed of plume advancement. 相似文献
7.
J. E. Houseworth 《Transport in Porous Media》2012,91(3):813-831
The injection of supercritical CO2 through wells into deep brine reservoirs is a topic of interest for geologic carbon sequestration. The injected CO2 is predominantly immiscible with the brine and its low density relative to brine leads to strong buoyancy effects. The displacement
of brine by CO2 in general is a multidimensional, complex nonlinear problem that requires numerical methods to solve. The approximations
of vertical equilibrium and complete gravity segregation (sharp interface) have been introduced to reduce the complexity and
dimensionality of the problem. Furthermore, for the radial displacement process considered here, the problem can be formulated
in terms of a similarity variable that reduces spatial and temporal dependencies to a single variable. However, the resulting
ordinary differential equation is still nonlinear and exact solutions are not available. The existing analytical solutions
are approximations limited to certain parameter ranges that become inaccurate over a large portion of the parameter space.
Here, I use a matched boundary extrapolation method to provide much greater accuracy for analytical/semi-analytical approximations
over the full parameter range. 相似文献
8.
Kue-Young Kim Weon Shik Han Junho Oh Taehee Kim Jeong-Chan Kim 《Transport in Porous Media》2012,92(2):397-418
Mitigation and control of borehole pressure at the bottom of an injection well is directly related to the effective management
of well injectivity during geologic carbon sequestration activity. Researchers have generally accepted the idea that high
rates of CO2 injection into low permeability strata results in increased bottom-hole pressure in a well. However, the results of this
study suggested that this is not always the case, due to the occurrence of localized salt precipitation adjacent to the injection
well. A series of numerical simulations indicated that in some cases, a low rate of CO2 injection into high permeability formation induced greater pressure build-up. This occurred because of the different types
of salt precipitation pattern controlled by buoyancy-driven CO2 plume migration. The first type is non-localized salt precipitation, which is characterized by uniform salt precipitation
within the dry-out zone. The second type, localized salt precipitation, is characterized by an abnormally high level of salt
precipitation at the dry-out front. This localized salt precipitation acts as a barrier that hampers the propagation of both
CO2 and pressure to the far field as well as counter-flowing brine migration toward the injection well. These dynamic processes
caused a drastic pressure build-up in the well, which decreased injectivity. By modeling a series of test cases, it was found
that low-rate CO2 injection into high permeability formation was likely to cause localized salt precipitation. Sensitivity studies revealed
that brine salinity linearly affected the level of salt precipitation, and that vertical permeability enhanced the buoyancy
effect which increased the growth of the salt barrier. The porosity also affected both the level of localized salt precipitation
and dry-out zone extension depending on injection rates. High temperature injected CO2 promoted the vertical movement of the CO2 plume, which accelerated localized salt precipitation, but at the same time caused a decrease in the density of the injected
CO2. The combination of these two effects eventually decreased bottomhole pressure. Considering the injectivity degradation,
a method is proposed for decreasing the pressure build-up and increasing injectivity by assigning a ‘skin zone’ that represents
a local region with a transmissivity different from that of the surrounding aquifer. 相似文献
9.
Concern has been expressed that carbon dioxide (CO2) leaking from deep geological storage could adversely impact water quality in overlying potable aquifers by mobilizing hazardous
trace elements. In this article, we present a systematic evaluation of the possible water quality changes in response to CO2 intrusion into aquifers currently used as sources of potable water in the United States. The evaluation was done in three
parts. First, we developed a comprehensive geochemical model of aquifers throughout the United States, evaluating the initial
aqueous abundances, distributions, and modes of occurrence of selected hazardous trace elements in a large number of potable
groundwater quality analyses from the National Water Information System (NWIS) database. For each analysis, we calculated
the saturation indices (SIs) of several minerals containing these trace elements. The minerals were initially selected through
literature surveys to establish whether field evidence supported their postulated presence in potable water aquifers. Mineral
assemblages meeting the criterion of thermodynamic saturation were assumed to control the aqueous concentrations of the hazardous
elements at initial system state as well as at elevated CO2 concentrations caused by the ingress of leaking CO2. In the second step, to determine those hazardous trace elements of greatest concern in the case of CO2 leakage, we conducted thermodynamic calculations to predict the impact of increasing CO2 partial pressures on the solubilities of the identified trace element mineral hosts. Under reducing conditions characteristic
of many groundwaters, the trace elements of greatest concern are arsenic (As) and lead (Pb). In the final step, a series of
reactive-transport simulations was performed to investigate the chemical evolution of aqueous As and Pb after the intrusion
of CO2 from a storage reservoir into a shallow confined groundwater resource. Results from the reactive-transport model suggest
that a significant increase of aqueous As and Pb concentrations may occur in response to CO2 intrusion, but that the maximum concentration values remain below or close to specified maximum contaminant levels (MCLs).
Adsorption/desorption from mineral surfaces may strongly impact the mobilization of As and Pb. 相似文献
10.
Qinjun Kang Peter C. Lichtner Hari S. Viswanathan Amr I. Abdel-Fattah 《Transport in Porous Media》2010,82(1):197-213
We apply a multi-component reactive transport lattice Boltzmann model developed in previous studies for modeling the injection
of a CO2-saturated brine into various porous media structures at temperatures T = 25 and 80°C. In the various cases considered the porous medium consists initially of calcite with varying grain size and
shape. A chemical system consisting of Na+, Ca2+, Mg2+, H+, CO2°(aq){{\rm CO}_2^{\circ}{\rm (aq)}}, and Cl− is considered. Flow and transport by advection and diffusion of aqueous species, combined with homogeneous reactions occurring
in the bulk fluid, as well as the dissolution of calcite and precipitation of dolomite are simulated at the pore scale. The
effects of the structure of the porous media on reactive transport are investigated. The results are compared with a continuum-scale
model and the discrepancies between the pore- and continuum-scale models are discussed. This study sheds some light on the
fundamental physics occurring at the pore scale for reactive transport involved in geologic CO2 sequestration. 相似文献
11.
G. G. Tsypkin 《Fluid Dynamics》2018,53(5):680-689
The mechanism of replacement of methane by carbon dioxide in the hydrate in the process of CO2 injection into a reservoir with formation of fronts of methane hydrate dissociation and carbon dioxide hydrate generation is investigated. It is found that such a replacement regime can be implemented in both low- and high-permeability reservoirs. It is shown that in the highintensity injection regime the heat flux from the well does not affect propagation of the fronts of methane hydrate dissociation and carbon dioxide hydrate generation. In this case the replacement regime is maintained by only the heat released at formation of carbon dioxide hydrate. An increase in the injection pressure may lead to suppression of methane hydrate dissociation and termination of the replacement reaction. The critical diagrams of existence of the regime of conversion of methane hydrate to carbon dioxide hydrate are constructed. 相似文献
12.
For deep injection of CO2 in thick saline formations, the movements of both the free gas phase and dissolved CO2 are sensitive to variations in vertical permeability. A simple model for vertical heterogeneity was studied, consisting of
a random distribution of horizontal impermeable barriers with a given overall volume fraction and distribution of lengths.
Analytical results were obtained for the distribution of values for the permeability, and compared to numerical simulations
of deep CO2 injection and convection in heterogeneous formations, using multiple realizations for the permeability distribution. It is
shown that for a formation of thickness H, the breakthrough times in two dimensions for deep injection scale as H
2 for moderate injection rates. In comparison to heterogeneous shale distributions, a homogeneous medium with equivalent effective
vertical permeability has a longer breakthrough time for deep injection, and a longer onset time for convection. 相似文献
13.
Weon Shik Han Kue-Young Kim Richard P. Esser Eungyu Park Brian J. McPherson 《Transport in Porous Media》2011,90(3):807-829
The primary purpose of this study is to understand quantitative characteristics of mobile, residual, and dissolved CO2 trapping mechanisms within ranges of systematic variations in different geologic and hydrologic parameters. For this purpose,
we conducted an extensive suite of numerical simulations to evaluate the sensitivities included in these parameters. We generated
two-dimensional numerical models representing subsurface porous media with various permutations of vertical and horizontal
permeability (k
v and k
h), porosity (f{\phi}), maximum residual CO2 saturation (Sgrmax{S_{\rm gr}^{\max}}), and brine density (ρ
br). Simulation results indicate that residual CO2 trapping increases proportionally to kv, kh, Sgrmax{k_{\rm v}, k_{\rm h}, S_{\rm gr}^{\max}} and ρ
br but is inversely proportional to f.{\phi.} In addition, the amount of dissolution-trapped CO2 increases with k
v and k
h, but does not vary with f{\phi } , and decreases with Sgrmax{S_{\rm gr}^{\max}} and ρ
br. Additionally, the distance of buoyancy-driven CO2 migration increases proportionally to k
v and ρ
br only and is inversely proportional to kh, f{k_{\rm h}, \phi } , and Sgrmax{S_{\rm gr}^{\max}} . These complex behaviors occur because the chosen sensitivity parameters perturb the distances of vertical and horizontal
CO2 plume migration, pore volume size, and fraction of trapped CO2 in both pores and formation fluids. Finally, in an effort to characterize complex relationships among residual CO2 trapping and buoyancy-driven CO2 migration, we quantified three characteristic zones. Zone I, expressing the variations of Sgrmax{S_{\rm gr}^{\max}} and k
h, represents the optimized conditions for geologic CO2 sequestration. Zone II, showing the variation of f{\phi} , would be preferred for secure CO2 sequestration since CO2 has less potential to escape from the target formation. In zone III, both residual CO2 trapping and buoyancy-driven migration distance increase with k
v and ρ
br. 相似文献
14.
The two-dimensional problem of supercritical carbon dioxide injection into an aquifer is solved. Shocks and rarefaction waves propagating in a sequence from an injection well into the formation are described within the framework of a complete nonisothermal model of flows in a porous medium. In the approximation of isothermal immiscible water and carbon dioxide flow the hydrodynamic stability of the leading displacement front is investigated for various reservoir pressures and temperatures. The parameters of unstable fronts are determined using a sufficient instability condition formulated in analytic form. The approximate analytic results are supported by the direct numerical simulation of CO2 injection using the complete model in which thermal effects and phase transitions are taken into account. 相似文献
15.
On the basis of observations at four enhanced coalbed methane (ECBM)/CO2 sequestration pilots, a laboratory-scale study was conducted to understand the flow behavior of coal in a methane/CO2 environment. Sorption-induced volumetric strain was first measured by flooding fresh coal samples with adsorptive gases (methane
and CO2). In order to replicate the CO2–ECBM process, CO2 was then injected into a methane-saturated core to measure the incremental “swelling.” As a separate effort, the permeability
of a coal core, held under triaxial stress, was measured using methane. This was followed by CO2 flooding to replace the methane. In order to best replicate the conditions in situ, the core was held under uniaxial strain,
that is, no horizontal strain was permitted during CO2 flooding. Instead, the horizontal stress was adjusted to ensure zero strain. The results showed that the relative strain
ratio for CO2/methane was between 2 and 3.5. The measured volumetric strains were also fitted using a Langmuir-type model, thus enabling
calculation of the strain at any gas pressure and using the analytical permeability models. For permeability work, effort
was made to increase the horizontal stress to achieve the desired zero horizontal strain condition expected under in situ
condition, but this became impossible because the “excess” stress required to maintain this condition was very large, resulting
in sample failure. Finally, when CO2 was introduced and horizontal strain was permitted, permeability reduction was an order of magnitude greater, suggesting
that the “excess” stress would have reduced it significantly further. The positive finding of the work was that the “excess”
stresses associated with injection of CO2 are large. The excess stresses generated might be sufficient to cause microfracturing and increased permeability, and improved
injectivity. Also, there might be a weakening effect resulting from repeated CO2 injection, as has been found to be the case with thermal cycling of rocks. 相似文献
16.
Dissolution of CO2 into brine is an important and favorable trapping mechanism for geologic storage of CO2. There are scenarios, however, where dissolved CO2 may migrate out of the storage reservoir. Under these conditions, CO2 will exsolve from solution during depressurization of the brine, leading to the formation of separate phase CO2. For example, a CO2 sequestration system with a brine-permeable caprock may be favored to allow for pressure relief in the sequestration reservoir.
In this case, CO2-rich brine may be transported upwards along a pressure gradient caused by CO2 injection. Here we conduct an experimental study of CO2 exsolution to observe the behavior of exsolved gas under a wide range of depressurization. Exsolution experiments in highly
permeable Berea sandstones and low permeability Mount Simon sandstones are presented. Using X-ray CT scanning, the evolution
of gas phase CO2 and its spatial distribution is observed. In addition, we measure relative permeability for exsolved CO2 and water in sandstone rocks based on mass balances and continuous observation of the pressure drop across the core from
12.41 to 2.76 MPa. The results show that the minimum CO2 saturation at which the exsolved CO2 phase mobilization occurs is from 11.7 to 15.5%. Exsolved CO2 is distributed uniformly in homogeneous rock samples with no statistical correlation between porosity and CO2 saturation observed. No gravitational redistribution of exsolved CO2 was observed after depressurization, even in the high permeability core. Significant differences exist between the exsolved
CO2 and water relative permeabilities, compared to relative permeabilities derived from steady-state drainage relative permeability
measurements in the same cores. Specifically, very low CO2 and water relative permeabilities are measured in the exsolution experiments, even when the CO2 saturation is as high as 40%. The large relative permeability reduction in both the water and CO2 phases is hypothesized to result from the presence of disconnected gas bubbles in this two-phase flow system. This feature
is also thought to be favorable for storage security after CO2 injection. 相似文献
17.
HOUJian 《应用数学和力学(英文版)》2004,25(6):694-702
According to the research theory of improved black oil simulator, a practical mathematical model for C02 miscible flooding was presented. In the model, the miscible process simulation was realized by adjusting oil/gas relative permeability and effective viscosity under the condition of miscible flow. In order to predict the production performance fast, streamline method is employed to solve this model as an alternative to traditional finite difference methods. Based on streamline distribution of steady-state flow through porous media with complex boundary confirmed with the boundary element method (BEM), an explicit total variation diminishing (TVD) method is used to solve the one-dimensional flow problem. At the same time, influences of development scheme, solvent slug size, and injection periods on CO2 drive recovery are discussed. The model has the advantages of less information need, fast calculation, and adaptation to calculate CO2 drive performance of all kinds of patterns in a random shaped porous media with assembly boundary. It can be an effective tool for early stage screening andmiscible oil field.reservoir dynamic management of the CO2 miscible oil field. 相似文献
18.
V. A. Gorelov A. Yu. Kireev S. V. Shilenkov 《Journal of Applied Mechanics and Technical Physics》2005,46(2):160-167
Models of population of some radiating electron-vibrational states of CO, CN, and C2 molecules are developed. The characteristics of radiation in a chemically nonequilibrium flow behind the front of a strong shock wave in a mixture of gases constituting the Martian atmosphere are calculated. The numerical data are compared with experimental results.Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 46, No. 2, pp. 13–22, March–April, 2005 相似文献
19.
Geological sequestration of CO2 offers a promising solution for reducing net emissions of greenhouse gases into the atmosphere. This emerging technology
must make it possible to inject CO2 into deep saline aquifers or oil- and gas-depleted reservoirs in the supercritical state (P > 7.4MPa and T > 31.1°C) to achieve a higher density and therefore occupy less volume underground. Previous experimental and numerical simulations
have demonstrated that massive CO2 injection in saline reservoirs causes a major disequilibrium of the physical and geochemical characteristics of the host
aquifer. The near-well injection zone seems to constitute an underground hydrogeological system particularly impacted by supercritical
CO2 injection and the most sensitive area, where chemical phenomena (e.g. mineral dissolution/precipitation) can have a major
impact on the porosity and permeability. Furthermore, these phenomena are highly sensitive to temperature. This study, based
on numerical multi-phase simulations, investigates thermal effects during CO2 injection into a deep carbonate formation. Different thermal processes and their influence on the chemical and mineral reactivity
of the saline reservoir are discussed. This study underlines both the minor effects of intrinsic thermal and thermodynamic
processes on mineral reactivity in carbonate aquifers, and the influence of anthropic thermal processes (e.g. injection temperature)
on the carbonates’ behaviour. 相似文献
20.
Zhou Na Tetsuya Suekane Takahiro Hosokawa Sadamu Inaoka Qiuwang Wang 《Transport in Porous Media》2011,90(2):575-587
Co-injection of water with CO2 is an effective scheme to control initial gas saturation in porous media. A fractional flow rate of water of approximately
5–10% is sufficient to reduce initial gas saturations. After water injection following the co-injection, most of the gas injected
in the porous media is trapped by capillarity with a low fractional volume of migrating gas. In this study, we first derive
an analytical model to predict the gas saturation levels for co-injection with water. The initial gas saturation is controlled
by the fractional flow ratio in the co-injection process. Next, we experimentally investigate the effect of initial gas saturation
on residual gas saturation at capillary trapping by co-injecting gas and water followed by pure water injection, using a water
and nitrogen system at room temperature. Depending on relative permeability, initial gas saturation is reduced by co-injection
of water. If the initial saturation in the Berea sandstone core is controlled at 20–40%, most of the gas is trapped by capillarity,
and less than 20% of the gas with respect to the injected gas volume is migrated by water injection. In the packed bed of
Toyoura standard sand, the initial gas saturation is approximately 20% for a wide range of gas with a fractional flow rate
from 0.50 to 0.95. The residual gas saturation for these conditions is approximately 15%. Less than approximately 25% of the
gas migrates by water injection. The amount of water required for co-injection systems is estimated on the basis of the analytical
model and experimental results. 相似文献