共查询到20条相似文献，搜索用时 922 毫秒
1.
Mohamad R. Soltanian Mohammad A. Amooie David R. Cole Thomas H. Darrah David E. Graham Susan M. Pfiffner Tommy J. Phelps Joachim Moortgat 《Ground water》2018,56(2):176-186
In the context of geological carbon sequestration (GCS), carbon dioxide (CO2) is often injected into deep formations saturated with a brine that may contain dissolved light hydrocarbons, such as methane (CH4). In this multicomponent multiphase displacement process, CO2 competes with CH4 in terms of dissolution, and CH4 tends to exsolve from the aqueous into a gaseous phase. Because CH4 has a lower viscosity than injected CO2, CH4 is swept up into a ‘bank’ of CH4‐rich gas ahead of the CO2 displacement front. On the one hand, this may provide a useful tracer signal of an approaching CO2 front. On the other hand, the emergence of gaseous CH4 is undesirable because it poses a leakage risk of a far more potent greenhouse gas than CO2 if the cap rock is compromised. Open fractures or faults and wells could result in CH4 contamination of overlying groundwater aquifers as well as surface emissions. We investigate this process through detailed numerical simulations for a large‐scale GCS pilot project (near Cranfield, Mississippi) for which a rich set of field data is available. An accurate cubic‐plus‐association equation‐of‐state is used to describe the non‐linear phase behavior of multiphase brine‐CH4‐CO2 mixtures, and breakthrough curves in two observation wells are used to constrain transport processes. Both field data and simulations indeed show the development of an extensive plume of CH4‐rich (up to 90 mol%) gas as a consequence of CO2 injection, with important implications for the risk assessment of future GCS projects. 相似文献
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Vertically integrated models are frequently applied to study subsurface flow related to CO2 storage scenarios in saline aquifers. In this paper, we study the impact of capillary-pressure hysteresis and CO2 trapping on the integrated constitutive parameter functions. Our results show that for the initial drainage and a subsequent imbibition, trapping is the dominant contributor to hysteresis in integrated models. We also find that for advective processes like injection and plume migration in a sloped aquifer the correct treatment of the hysteretic nature of the capillary fringe is likely of secondary importance. However, for diffusive/dispersive processes such as a redistribution of the CO2 plume due to buoyancy and capillary forces, the hysteretic nature of the capillary fringe may significantly impact the final distribution of the fluids and the timescale of the redistribution. 相似文献
3.
Geological storage of carbon dioxide (CO2) is a promising technology for reducing atmospheric emissions. The large discrepancy in the time- and length-scales between up-dip migration of buoyant supercritical CO2 and the sinking fingers of dissolved CO2 poses a challenge for numerical simulations aimed at describing the fate of the plume. Hence, several investigators have suggested methods to simplify the problem, but to date there has been no reference solution with which these simplified models can be compared. We investigate the full problem of Darcy-based two-phase flow with gravity-current propagation and miscible convective mixing, using high-resolution numerical simulations. We build on recent developments of the Automatic Differentiation - General Purpose Research Simulator (AD-GPRS) at Stanford. The results show a CO2 plume that travels for 5000 years reaching a final distance of 14 km up-dip from the injection site. It takes another 2000 years before the CO2 is completely trapped as residual (40%) and dissolved (60%) CO2. Dissolution causes a significant reduction of the plume speed. While fingers of dissolved CO2 appear under the propagating gravity current, the resident brine does not become fully saturated with CO2 anywhere under the plume. The overall mass transfer of CO2 into the brine under the plume remains practically constant for several thousands of years. These results can be used as a benchmark for verification, or improvements, of simplified (reduced-dimensionality, upscaled) models. Our results indicate that simplified models need to account for: (i) reduced dissolution due to interaction with the plume, and (ii) gradual reduction of the local dissolution rate after the fingers begin to interact with the bottom of the aquifer. 相似文献
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Understanding multiphase transport within saline aquifers is necessary for safe and efficient CO2 sequestration. To that end, numerous full‐physics codes exist for rigorously modeling multiphase flow within porous and permeable rock formations. High‐fidelity simulation with such codes is data‐ and computation‐intensive, and may not be suitable for screening‐level calculations. Alternatively, under conditions of vertical equilibrium, a class of sharp‐interface models result in simplified relationships that can be solved with limited computing resources and geologic/fluidic data. In this study, the sharp‐interface model of Nordbotten and Celia (2006a,2006b) is evaluated against results from a commercial full‐physics simulator for a semi‐confined system with vertical permeability heterogeneity. In general, significant differences were observed between the simulator and the sharp‐interface model results. A variety of adjustments were made to the sharp‐interface model including modifications to the fluid saturation and effective viscosity in the two‐phase region behind the CO2‐brine interface. These adaptations significantly improved the predictive ability of the sharp interface model while maintaining overall tractability. 相似文献
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Deep saline aquifers are important geological formations for CO2 sequestration. It has been known that dissolution of CO2 increases brine density, which results in downward density-driven convection and consequently greatly enhances CO2 sequestration. In this study, a continuum-scale lattice Boltzmann model is used to investigate convective mixing of CO2 in saline aquifers. It is found that increasing permeability in either the vertical or horizontal direction accelerates the development of convective mixing. In a heterogeneous aquifer, increasing heterogeneity hampers the onset of convective mixing, because the heterogeneous permeability field results in a large portion of low-velocity region which reduces the instability of the system. The critical time for the onset of instability depends mainly on the coefficient of variation (COV) of the permeability field, and is insensitive to the correlation length. This implies that within the scale of critical time, mass transport is dominated by diffusion, and thus depends mainly on fine-scale heterogeneity controlled by COV. We derived an empirical formula for estimating the critical time, which leads to good estimates for all combinations of COV and correlation length. Fingering, channeling, and dispersion are the three mechanisms for mass transport. In dispersion, dissolved mass is approximately proportional to the square root of time, while in fingering and channeling it is approximately proportional to time. Mass transport by channeling depends significantly on permeability structure, while by fingering it is controlled by gravitational instability. It is also found that larger volumes of CO2 can be stored in heterogeneous aquifers because of higher mass dissolution rates. 相似文献
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Telogenetic epikarst carbon sourcing and transport processes and their associated hydrogeochemical responses are complex and dynamic. Carbon dioxide (CO2) transport rates in the epikarst zone are often driven by hydrogeochemical responses, which influence carbonate dissolution and conduit formation. This study examines the influence of land use on carbon sourcing and carbonate dissolution kinetics through a comparative analysis of separate, but similar, epikarst systems in south-central Kentucky. The use of high-resolution hydrogeochemical data from multiple data loggers and isotope analysis from collected water samples reflects the processes within these epikarst aquifers, which are estimated to contribute significantly to bedrock dissolution. Results indicate that, in an agricultural setting, long-term variability and dissolution is governed by seasonal production of CO2 . In a more urbanized, shallower epikarst system, land cover may affect CO2 transport between the soil and underlying bedrock. This concentration of CO2 potentially contributes to ongoing dissolution and conduit development, irrespective of seasonality. The observed responses in telogenetic epikarst systems seem to be more similar to eogenetic settings, which is suggested to be driven by CO2 transport occurring independent of high matrix porosity. The results of this study indicate site-specific responses with respect to both geochemical and δ13CDIC changes on a seasonal scale, despite regional geologic similarities. The results indicate that further comparative analyses between rural and urban landscapes in other karst settings is needed to delineate the impact of land use and seasonality on dissolution and carbon sourcing during karst formation processes. © 2019 John Wiley & Sons, Ltd. 相似文献
8.
Quanlin Zhou Jens T. Birkholzer Edward Mehnert Yu-Feng Lin Keni Zhang 《Ground water》2010,48(4):494-514
Integrated modeling of basin- and plume-scale processes induced by full-scale deployment of CO2 storage was applied to the Mt. Simon Aquifer in the Illinois Basin. A three-dimensional mesh was generated with local refinement around 20 injection sites, with approximately 30 km spacing. A total annual injection rate of 100 Mt CO2 over 50 years was used. The CO2-brine flow at the plume scale and the single-phase flow at the basin scale were simulated. Simulation results show the overall shape of a CO2 plume consisting of a typical gravity-override subplume in the bottom injection zone of high injectivity and a pyramid-shaped subplume in the overlying multilayered Mt. Simon, indicating the important role of a secondary seal with relatively low-permeability and high-entry capillary pressure. The secondary-seal effect is manifested by retarded upward CO2 migration as a result of multiple secondary seals, coupled with lateral preferential CO2 viscous fingering through high-permeability layers. The plume width varies from 9.0 to 13.5 km at 200 years, indicating the slow CO2 migration and no plume interference between storage sites. On the basin scale, pressure perturbations propagate quickly away from injection centers, interfere after less than 1 year, and eventually reach basin margins. The simulated pressure buildup of 35 bar in the injection area is not expected to affect caprock geomechanical integrity. Moderate pressure buildup is observed in Mt. Simon in northern Illinois. However, its impact on groundwater resources is less than the hydraulic drawdown induced by long-term extensive pumping from overlying freshwater aquifers. 相似文献
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The first post‐injection seismic monitor survey at the Ketzin pilot CO2 storage site: results from time‐lapse analysis 
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下载免费PDF全文 Fei Huang Peter Bergmann Christopher Juhlin Monika Ivandic Stefan Lüth Alexandra Ivanova Thomas Kempka Jan Henninges Daniel Sopher Fengjiao Zhang 《Geophysical Prospecting》2018,66(1):62-84
The injection of CO2 at the Ketzin pilot CO2 storage site started in June 2008 and ended in August 2013. During the 62 months of injection, a total amount of about 67 kt of CO2 was injected into a saline aquifer. A third repeat three‐dimensional seismic survey, serving as the first post‐injection survey, was acquired in 2015, aiming to investigate the recent movement of the injected CO2. Consistent with the previous two time‐lapse surveys, a predominantly west–northwest migration of the gaseous CO2 plume in the up‐dip direction within the reservoir is inferred in this first post‐injection survey. No systematic anomalies are detected through the reservoir overburden. The extent of the CO2 plume west of the injection site is almost identical to that found in the 2012 second repeat survey (after injection of 61 kt); however, there is a significant decrease in its size east of the injection site. Assessment of the CO2 plume distribution suggests that the decrease in the size of the anomaly may be due to multiple factors, such as limited vertical resolution, CO2 dissolution, and CO2 migration into thin layers, in addition to the effects of ambient noise. Four‐dimensional seismic modelling based on dynamic flow simulations indicates that a dynamic balance between the newly injected CO2 after the second repeat survey and the CO2 migrating into thin layers and being dissolved was reached by the time of the first post‐injection survey. In view of the significant uncertainties in CO2 mass estimation, both patchy and non‐patchy saturation models for the Ketzin site were taken into consideration. 相似文献
10.
Karl W. Bandilla Michael A. Celia Jens T. Birkholzer Abdullah Cihan Evan C. Leister 《Ground water》2015,53(3):362-377
Geologic carbon sequestration (GCS) is being considered as a climate change mitigation option in many future energy scenarios. Mathematical modeling is routinely used to predict subsurface CO2 and resident brine migration for the design of injection operations, to demonstrate the permanence of CO2 storage, and to show that other subsurface resources will not be degraded. Many processes impact the migration of CO2 and brine, including multiphase flow dynamics, geochemistry, and geomechanics, along with the spatial distribution of parameters such as porosity and permeability. In this article, we review a set of multiphase modeling approaches with different levels of conceptual complexity that have been used to model GCS. Model complexity ranges from coupled multiprocess models to simplified vertical equilibrium (VE) models and macroscopic invasion percolation models. The goal of this article is to give a framework of conceptual model complexity, and to show the types of modeling approaches that have been used to address specific GCS questions. Application of the modeling approaches is shown using five ongoing or proposed CO2 injection sites. For the selected sites, the majority of GCS models follow a simplified multiphase approach, especially for questions related to injection and local‐scale heterogeneity. Coupled multiprocess models are only applied in one case where geomechanics have a strong impact on the flow. Owing to their computational efficiency, VE models tend to be applied at large scales. A macroscopic invasion percolation approach was used to predict the CO2 migration at one site to examine details of CO2 migration under the caprock. 相似文献
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Deep saline aquifers are one of the most suitable geologic formations for carbon sequestration. The linear and global stability analysis of the time-dependent density-driven convection in deep saline aquifers is presented for long-term storage of carbon dioxide (CO2). The convective mixing that can greatly accelerate the CO2 dissolution into saline aquifers arises because the density of brine increases upon the dissolution of CO2 and such a density difference may induce instability. The effects of anisotropic permeability on the stability criteria, such as the critical time for the appearance of convective phenomena and the critical wavelength of the most unstable perturbation, are investigated with linear and global stability analysis. The linear stability analysis provides a sufficient condition for instability while the global stability analysis yields a sufficient condition for stability. The results obtained from these two approaches are not exactly the same but show a consistent trend, both indicating that the anisotropic system becomes more unstable when either the vertical or horizontal permeability increases. 相似文献
12.
The standard approach for geologic storage of CO2 consists of injecting it as a supercritical CO2 phase. This approach places stringent requirements on the caprock, which must display: (1) high entry pressure to prevent the buoyancy driven upwards escape of CO2; (2) low permeability to minimize the upwards flux of brine displaced by the CO2; and (3) high strength to ensure that pressure build up does not cause caprock failure. We propose an alternative approach for cases when the above requirements are not met. The approach consists of extracting brine from the storage formation and then re-injecting it so that it mixes with CO2 at depth in the injection well. Mixing at depth reduces the pressure required for brine and CO2 at the surface. This CO2-saturated brine will sink to the aquifer bottom because it is denser than resident brine, which eliminates the risk of buoyant escape of CO2. The method is particularly favorable when the aquifer dips, because CO2-saturated brine will tend to flow downslope. We perform two- and three-dimensional numerical simulations to study how far upslope the extraction well needs to be located to ensure a very long operation without CO2 ever breaking through. Several sets of simulations were carried out to evaluate the effect of slope, temperature, pressure and CO2 concentration, which is significantly reduced if flue gas (i.e., without capture) is mixed with the brine. We analyze energy requirements to find that the system requires high permeability to be viable, but its performance is improved by taking advantage of the thermal energy of the extracted brine. 相似文献
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This study presents the impact of fractures on CO2 transport, capillary pressure and storage capacity by conducting both experimental and numerical studies. A series of laboratory experiment tests was designed with both a homogeneous and a fractured core under CO2 storage conditions. The experimental results reveal a piston-like brine displacement with gravity override effects in the homogeneous core regardless of CO2 injection rates. In the fractured core, however, two distinctive types of brine displacements were observed; one showing brine displacement only in the fracture whereas the other shows brine displacement both in the fracture and matrix with different rates, which were dependent on the magnitude of the pressure build-up in the matrix. The injectivity in the fractured core was twice of the homogeneous core, while the amount of calculated CO2 in the homogeneous core was over 1.5 times greater than the fractured core. Salt precipitation, which is likely to occur near injection wells, was observed in the experiments; X-ray images enabled the observation of salt-precipitation during CO2-flooding tests. Finally, numerical simulations predict free-phase CO2 transfer between fracture and matrix in a fracture-matrix system. Pressure gradients between the fracture and matrix enforced CO2 to transfer from the fracture into matrix at the front of the CO2 plume, whereas, the reversal of pressure gradients at the rear zone of the CO2 plume reversed the transfer process. The variation of CO2 saturation within the fracture was caused by fracture aperture variations, and local variations of fracture permeability control the free-phase CO2 transfer between the fracture and matrix. 相似文献
14.
The effectiveness of CO2 storage in deep saline aquifers and hydrocarbon reservoirs is governed, among other factors, by the interfacial tension between the injected CO2 and formation water (brine). Experimental data on CO2/water and CO2/NaCl solution have revealed that the interfacial tension depends on the pressure, temperature and water salinity. However, there is still a lack of data for other salts (such as MgCl2 and CaCl2) which are also present in aquifers and carbonate reservoirs. 相似文献
15.
Predicting and quantifying impacts of potential carbon dioxide (CO2) leakage into shallow aquifers that overlie geologic CO2 storage formations is an important part of developing reliable carbon storage techniques. Leakage of CO2 through fractures, faults or faulty wellbores can reduce groundwater pH, inducing geochemical reactions that release solutes into the groundwater and pose a risk of degrading groundwater quality. In order to help quantify this risk, predictions of metal concentrations are needed during geologic storage of CO2. Here, we present regional-scale reactive transport simulations, at relatively fine-scale, of CO2 leakage into shallow aquifers run on the PFLOTRAN platform using high-performance computing. Multiple realizations of heterogeneous permeability distributions were generated using standard geostatistical methods. Increased statistical anisotropy of the permeability field resulted in more lateral and vertical spreading of the plume of impacted water, leading to increased Pb2+ (lead) concentrations and lower pH at a well down gradient of the CO2 leak. Pb2+ concentrations were higher in simulations where calcite was the source of Pb2+ compared to galena. The low solubility of galena effectively buffered the Pb2+ concentrations as galena reached saturation under reducing conditions along the flow path. In all cases, Pb2+ concentrations remained below the maximum contaminant level set by the EPA. Results from this study, compared to natural variability observed in aquifers, suggest that bicarbonate (HCO3−) concentrations may be a better geochemical indicator of a CO2 leak under the conditions simulated here. 相似文献
16.
During geologic storage of carbon dioxide (CO2), trapping of the buoyant CO2 after injection is essential in order to minimize the risk of leakage into shallower formations through a fracture or abandoned well. Models for the subsurface behavior of the CO2 are useful for the design, implementation, and long-term monitoring of injection sites, but traditional reservoir-simulation tools are currently unable to resolve the impact of small-scale trapping processes on fluid flow at the scale of a geologic basin. Here, we study the impact of solubility trapping from convective dissolution on the up-dip migration of a buoyant gravity current in a sloping aquifer. To do so, we conduct high-resolution numerical simulations of the gravity current that forms from a pair of miscible analogue fluids. Our simulations fully resolve the dense, sinking fingers that drive the convective dissolution process. We analyze the dynamics of the dissolution flux along the moving CO2–brine interface, including its decay as dissolved buoyant fluid accumulates beneath the buoyant current. We show that the dynamics of the dissolution flux and the macroscopic features of the migrating current can be captured with an upscaled sharp-interface model. 相似文献
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The typical shape of a capillary-pressure curve is either convex (e.g., Brooks–Corey model) or S-shaped (e.g., van Genuchten model). It is not universally agreed which model reflects natural rocks better. The difference between the two models lies in the representation of the capillary entry pressure. This difference does not lead to significantly different simulation results for modeling CO2 sequestration in aquifers without considering CO2 dissolution. However, we observe that the van-Genuchten-type capillary-pressure model accelerates CO2 solubility trapping significantly compared with the Brooks–Corey-type model. We also show that the simulation results are very sensitive to the slope of the van-Genuchten-type curve around the entry-pressure region. For the representative examples we study, the differences can be so large as to have complete dissolution of the CO2 plume versus persistence of over 50% of the plume over a 5000-year period.The cause of such sensitivity to the capillary-pressure model is studied. Particularly, we focus on how the entry pressure is represented in each model. We examine the mass-transfer processes under gravity-capillary equilibrium, molecular diffusion, convective mixing, and in the presence of small-scale heterogeneities. Laboratory measurement of capillary-pressure curves and some important implementation issues of capillary-pressure models in numerical simulators are also discussed. Most CO2 sequestration simulations in the literature employ one of the two capillary-pressure models. It is important to recognize that these two representations lead to very different predictions of long-term CO2 sequestration. 相似文献
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Contact angle is a principal control of the flow of multiple fluid phases through porous media; however its measurement on other than flat surfaces remains a challenge. A new method is presented for the measurement of the contact angle between immiscible fluids at the pore scale at reservoir conditions (10 MPa and 50 °C) inside a quarry limestone through the use of X-ray microtomography. It is applied to a super-critical CO2–brine–carbonate system by resampling the micro-CT data onto planes orthogonal to the contact lines, allowing for vectors to be traced along the grain surface and the CO2–brine interface. A distribution of contact angles ranging from 35° to 55° is observed, indicating that the CO2–brine–carbonate system is weakly water-wet. This range of contact angles can be understood as the result of contact angle hysteresis and surface heterogeneity on a range of length scales. Surface heterogeneity is examined by comparison of micro-CT results with optical thin sections and SEM images. 相似文献
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We suggest that different equations of state (EOS) algorithms can and frequently will provide very different predictions of CO2 migration following injection for sequestration. Rather than carry out an exhaustive examination of all EOS algorithms available, we elected to evaluate this general hypothesis by making detailed comparisons of simulation results of two very common EOS algorithms. We simulated and compared CO2 migration patterns using two fundamentally different EOS algorithms – Modified Redlich-Kwong EOS (MRKEOS) and Span and Wagner EOS (SWEOS). In general, the predictions of thermophysical properties for both algorithms are close, except for a contrast in the predicted fugacity coefficient of CO2, which subsequently propagates to a contrast in predicted solubility in water/brine. Typically, MRKEOS underestimates solubility of CO2 compared to both SWEOS and experimental solubility data. In simulations of CO2 migration, dissolution rates of separate-phase CO2 predicted from the two EOS algorithms were significantly different, even for small contrasts in predicted fluid properties from EOS algorithms, resulting in markedly different migration patterns. 相似文献