Plume Movement Research Articles

Investigating the Influence of Geological Heterogeneity on Capillary Trapping of Buoyant CO2 Using Transmitted-light Flow Visualization Experiments

Small scale heterogeneity characteristic of clastic formations has been well known to affect CO2 migration pathways during geologic carbon sequestration. Especially far field from the injection sites, when buoyancy and capillary forces take over from the injection pressure gradients, the effects of such geological features on the CO2 plume movement become compounded. Numerical simulations have established that accumulation and trapping of the buoyant plume is primarily due to the contrast in capillary entry pressures of different rock layers. Capillary trapping can help maximize the storage capacity of reservoirs and hence it is essential to understand the dynamics of CO2 movement and trapping under the influence of small scale heterogeneity and quantify its effects. In this work we propose buoyancy driven migration experiments and simulations conducted at the meter scale using glass beads packed in a quasi 2D glass cell. Using a combination of two linear axis actuators, we demonstrate an automated glass bead filler system that can generate 2D heterogeneous structures in a reproducible manner. A fluid pair that mimics the phase densities and viscosities of CO2-Brine at reservoir pressures and temperatures is employed. Light transmission technique is used for visualization, and to calibrate and quantify saturation of the trapped non-wetting fluid during the experiments. Invasion Percolation is used to simulate the buoyancy driven flow. With the ability to generate different types of heterogeneous structures in a reproducible manner, and by comparing experiments and simulations, a systematic investigation of the effect of heterogeneity on capillary trapping becomes possible.

Saturation time dependency of liquid and supercritical CO2 permeability of bituminous coals: Implications for carbon storage

Various types of lithospheric geological reservoirs are available for the safe and long-term storage of CO2. The phase of CO2 transitions between liquid and supercritical (mostly supercritical for depths greater than 800m) when injected into the subsurface. This high-density super-critical phase prevents CO2 molecules from upward diffusion toward the surface. Many questions arise in the context of coal seam sequestration with respect to its capacity, injectivity, plume movement, and leakage assessment. This work examines the effect of various saturation periods on the permeability evolution of porous coal. In this triaxial study, liquid and supercritical CO2, along with N2 were injected into a coal sample from the Jharia coal field (Jharkhand state, India). It was observed that the permeability reduction for liquid CO2 was 25%, 13.5% and 1% for 0–20h phase, 20–40h phase and 40–60h phase, respectively. For supercritical CO2, the reduction was observed to be 42.5%, 38.4% and 11%, respectively, for the three saturation cycles. The findings highlight that while high CO2 sorption in supercritical phase stores more of the adsorbate, the reduction in permeability slows down injection operation and the saturation induced coal expansion threatens the overall stability of the system.

Ammonium Concentration and Migration in Groundwater in the Vicinity of Waste Management Site Located in the Neighborhood of Protected Areas of Warsaw, Poland

The purpose of the present paper is to assess groundwater contamination by ammonium originating from the waste management site (including composting plant and the landfill) located in the vicinity of protected areas. In this paper, the impact of urban and industrial facilities adjacent to the landfill is also investigated. The analysis of ammonium concentration was carried out for selected piezometers and then the monitoring and laboratory tests results were referred to the Polish standards of groundwater quality. The content of the paper discusses the changes of ammonium concentration in time and space and presents potential reasons for these changes, especially resulting from the construction of the vertical bentonite barrier. The results show the significant decrease of ammonium concentration and progressive improvement of water quality observed in almost every piezometer after a few years since the vertical barrier has been installed. Furthermore, the paper provides statistical analyses of groundwater monitoring data from the period 1998–2015 in order to control the groundwater quality and assess the movement of contamination plume in the landfill area.

Impacts of relative permeability formulation on forecasts of CO2 phase behavior, phase distribution, and trapping mechanisms in a geologic carbon storage reservoir*

AbstractA critical aspect in the risk assessment of geologic carbon storage, a carbon‐emissions reduction method under extensive review and testing, is effective multiphase CO2 flow and transport simulation. Relative permeability is a flow parameter particularly critical for accurate forecasting of the multiphase behavior of CO2 in the subsurface. The relative permeability relationship assumed and especially the residual saturation of the gas phase greatly impacts predicted CO2 trapping mechanisms and long‐term plume migration behavior. A primary goal of this study was to evaluate the impact of the selection of relative permeability formulations on the efficacy of regional‐scale CO2 sequestration models. To accomplish this, we selected the San Rafael Swell area of East‐central Utah as a case study to evaluate the impact of relative permeability formulations on CO2 plume movement and behavior. A 2D vertical cross section model was built to simulate injection of CO2 into a brine aquifer for 30 years followed by 970 years of post‐injection monitoring. We evaluated five different relative permeability relationships to quantify their relative impacts on forecasted flow results of the model, with all other parameters maintained uniform and constant. Because of the interdependence between phase saturation and relative permeability in numerical simulations we expected to see some variation in phase behavior, phase distribution, and CO2 trapping mechanisms. An almost 60% difference in residually trapped gas was observed across the different relative permeability relationships. Large variations of up to 40% in the saturation of both dissolved phase and mobile supercritical phase CO2 were also observed. The pressure buildup and decay observed was not significantly affected by the relative permeability formulation until after injection pressures have dissipated. Results of this analysis suggest that CO2 plume movement and behavior are significantly dependent on the specific relative permeability formulation assigned, including the assumed residual saturation values of CO2 and brine. More specifically, different relative permeability relationships translate to significant differences in CO2 plume behavior and corresponding trapping mechanisms. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd

Effects of tides on the cross-isobath movement of the low-salinity plume in the western Yellow and East China Seas in winter

Offshore extension of the fresh Subei coast water is identified in winter based on in site salinity observation data in this and previous studies. A high-resolution regional ocean circulation model is used to investigate the cross-isobath movement of low salinity-water over the Yellow and East China Seas, and it has reproduced the salinity distribution observed in the winter of 2014–2015 successfully. The model suggests that the low-salinity water is basically degenerated back to the eastern coast of China in winter because of strong northeasterly wind. However, a part of the low-salinity water extends offshore in the southeast direction across the 20–50m isobaths over the Yangtze Bank, which cannot be explained by either the northerly winter monsoon or the Changjiang discharge. Numerical experiments suggest that the cross-isobath transport of the soluble substances is highly attributed to the tidal residual current, flowing southeastward across 20–50m isobaths over the whole Yangtze Bank. The results of controlled experiments also indicate that the bottom shear of the tidal current, rather than the tidal mixing, plays a significant role in the cross-isobath current during winter.

Satellite based detection of Volcanic SO2 over Pakistan

<div> <p>The present study is carried out to explain the presence of large concentrations of SO<sub>2</sub> in atmosphere of Pakistan during June, 2011. Large volcanic eruptions are a major source of greenhouse and trace gases. The eruption of Mount Nabro in June, 2011 injected large amount of SO<sub>2 </sub>into stratosphere. Nabro volcanic eruption generated a layer of sulfate aerosols, which resided in stratosphere for months. The total amount of SO<sub>2 </sub>that was injected into the atmosphere was estimated to be 1.3-2.0 Tg. Data products of Global Ozone Monitoring Experiment (GOME-2), Ozone Monitoring Instrument (OMI) and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) were used to study SO<sub>2</sub> concentrations and plume movement over Pakistan. HYSPLIT backward trajectory model is utilized to study the origin of SO<sub>2</sub> plume. The study confirms that SO<sub>2</sub> plume originated from Nabro volcanic eruption and caused significant atmospheric perturbations and affected the air quality of Pakistan. SO<sub>2</sub> emissions from volcanic eruptions can pose serious hazard to population as well as global climate.</p> </div> <p> </p>

A modelling investigation of solute transport in permeable porous media containing a discrete preferential flow feature

Preferential flow features (PFFs, e.g. fractures and faults) are common features in rocks that otherwise have significant matrix permeability. Despite this, few studies have explored the influence of a PFF on the distribution of solute plumes in permeable rock formations, and the current understanding of PFF effects on solute plumes is based almost entirely on low-permeability rock matrices. This research uses numerical modelling to examine solute plumes that pass through a PFF in permeable rock, to explore the PFF's influence on plume migration. The study adopts intentionally simplified arrangements involving steady-state solute plumes in idealised, moderate-to-high-permeability rock aquifers containing a single PFF. A range of matrix-PFF permeability ratios (4.9×10−6–2.5×10−2), typical of fractured sedimentary aquifers, is considered. The results indicate that for conditions representative of high-to-moderate-permeability sedimentary rock matrices containing a medium-sized fracture, the effect of the PFF on solute plume displacement and spreading can be considerable. For example, plumes are between 1.3 and 19 times wider than in associated porous media only scenarios, and medium-sized PFFs in moderately permeable matrices can reduce the maximum solute concentration by up to 104 times. Plume displacement and spreading is lower in aquifers of higher matrix-PFF permeability ratios, and where solute plumes are more dispersed at the point of intersection with the PFF. Asymmetry in the plume caused by the passage through the PFF is more pronounced for more dispersive plumes. The current study demonstrates that PFFs most likely govern solute plume characteristics in typical permeable matrices, given that a single PFF of aperture representing a medium-sized fracture (i.e. 5.0×10−4m) produces the equivalent spreading effects of 0.22–7.88m of plume movement through the permeable matrix.

Ice-proximal Labrador Sea Heinrich layers: a sedimentological approach

During Late Pleistocene Heinrich events (H-events), distinct, decimetre- to centimetre-thick layers of ice-rafted debris (IRD) were deposited in the North Atlantic as Heinrich layers (H-layers). These layers are characterized by high detrital carbonate content, low foraminifera content, a high percentage of Neogloboquadrina pachyderma (sinistral) among the planktonic foraminifera, high magnetic susceptibility, and high grey colour values. In contrast, H-layers in the Labrador Sea reach metre thickness at core sites proximal to the iceberg source off the Hudson Strait ice stream (HSIS), and show low magnetic susceptibility and relatively low grey levels on the colour scale. To provide the reader with some background information, four hypotheses concerning the origin of H-events are discussed at the outset: (1) the binge–purge (internal forcing) model, (2) the subglacial outburst flood model, (3) the external forcing model, and (4) the catastrophic ice shelf breakup model. The higher thickness of ice-proximal H-layers is due to the supply of large amounts of terrigenous sediments that were eroded from country rocks underlying the northeastern sector of the Laurentide Ice Sheet (LIS). These sediments were transported to the deep Labrador Sea by the efficient processes of bottom-following mass and surface plume movement, where they mixed with ice-rafted sediment. Four distinct depositional facies of H-layers (Types I to IV) have been identified: Type I H-layers occur within 300 km from the presumed HSIS terminus and consist of stacked thin layers of graded muds containing IRD. The graded muds that are spiked with IRD are the result of deposition of fine-grained sediment from lofting sediment columns that collected dropstones and grains under the iceberg route. Type II H-layers occur on the slope and rise at a greater distance south of the Hudson Strait outlet, on the levees of tributary canyons to the Northwest Atlantic Mid-Ocean Channel (NAMOC). These layers consist of alternating thin mud turbidites with intercalated laminae of IRD. Type III H-layers exist on the levees of the main channel of the NAMOC, and consist of layers of IRD alternating with fewer fine-grained spillover turbidites, reflecting the lower spillover frequency from the deep channel compared to the less deep slope canyons. Type IV H-layers are made up of bioturbated hemipelagic muds with IRD, and occur in regions between canyons not reached by spillover turbidity currents, and in distal regions of the open ocean or on seamounts. The anomalously high thickness of individual H-layers on the slope and rise off Hudson Strait is explained by the transport of significant portions of H-layer sediment by suspended sediment columns lofted from sand-carrying freshwater turbidity currents (Type I), and by low density turbidity currents (Types II and III). Isopach maps for H-layers 1–3 give hints of the drift routes of the lofted suspended sediment during its ascent to the surface, and of iceberg drift directions in the Labrador Sea.

Advective diffusion of volcanic plume captured by dense GNSS network around Sakurajima volcano: a case study of the vulcanian eruption on July 24, 2012

Data from a dense GNSS network were used to investigate the temporal and spatial development of a volcanic plume during the eruptive event at Sakurajima volcano in Japan on July 24, 2012. We extracted the post-fit phase residuals (PPR) of ionosphere-free linear combinations for each satellite based on the precise point positioning (PPP) approach. Temporal and spatial PPR anomalies clearly detected the movement of the volcanic plume. The maximum height of the crossing points of anomalous PPR paths was determined to be approximately 4000 m. We also compared the estimated wet zenith tropospheric delay with the estimated PPR anomalies, which suggested that we might successfully extract the PPR anomalies caused by the eruptive event. We then compared the PPR with the signal-to-noise ratio (SNR) anomalies. Only the path passing just above the crater showed significant change in the SNR value, suggesting that the volcanic ash and the water vapor within the volcanic plume became separated after reaching a high altitude because of ash fall during the plume’s lateral movement. Each of the two observables might reflect different characteristics of the water vapor and volcanic ash.

Deformation-related volcanism in the Pacific Ocean linked to the Hawaiian–Emperor bend

Ocean islands, seamounts and volcanic ridges are thought to form above mantle plumes. Yet, this mechanism cannot explain many volcanic features on the Pacific Ocean floor and some might instead be caused by cracks in the oceanic crust linked to the reorganization of plate motions. A distinctive bend in the Hawaiian–Emperor volcanic chain has been linked to changes in the direction of motion of the Pacific Plate, movement of the Hawaiian plume, or a combination of both. However, these links are uncertain because there is no independent record that precisely dates tectonic events that affected the Pacific Plate. Here we analyse the geochemical characteristics of lava samples collected from the Musicians Ridges, lines of volcanic seamounts formed close to the Hawaiian–Emperor bend. We find that the geochemical signature of these lavas is unlike typical ocean island basalts and instead resembles mid-ocean ridge basalts. We infer that the seamounts are unrelated to mantle plume activity and instead formed in an extensional setting, due to deformation of the Pacific Plate. 40Ar/39Ar dating reveals that the Musicians Ridges formed during two time windows that bracket the time of formation of the Hawaiian–Emperor bend, 53–52 and 48–47 million years ago. We conclude that the Hawaiian–Emperor bend was formed by plate–mantle reorganization, potentially triggered by a series of subduction events at the Pacific Plate margins.

About this title ‐ Precambrian Basins of India: Stratigraphic and Tectonic Context

This Memoir provides a comprehensive review of the Precambrian basins of the four Archaean nuclei of India (Dharwar, Bastar, Singhbhum and Aravalli-Bundelkhand), encompassing descriptions of the time–space distribution of sedimentary–volcanic successions, the interrelationship between tectonics and sedimentation, and basin histories. Studies of 22 basins within the framework of an international basin classification scheme deepen an understanding of the basin architecture especially for cratonic basins. Most Indian sedimentary successions formed as cratonic to extensional-margin rift and thermal-sag basins, some reflecting mantle plume movement, subcrustal heating or far-field stress. This Memoir shows that Phanerozoic plate-tectonic and sequence stratigraphic principles can be applied to the Precambrian basins of large Archaean provinces. The differences between the stratigraphic architecture of the Indian Precambrian and examples of Phanerozoic basin-fill successions elsewhere are ascribed to variable rates and intensities of the controls on accommodation and sediment supply, and changes inherent in the evolution of the hydrosphere–atmosphere and biosphere systems.

Storage capacity enhancement and reservoir management using water extraction: Four site case studies

Water extraction from carbon dioxide (CO2) storage reservoirs may be a method to enhance storage capacity and to actively manage storage reservoirs. Previous investigations into the use of water extraction have utilized homogeneous models to assess the feasibility of this technology. This study addressed water extraction based on four hypothetical CO2 storage sites, which varied with respect to heterogeneous lithology, variable structure, and complex internal geometry. The simulation results showed the increased CO2 storage capacity achieved through the use of water extraction varies greatly based on site conditions, ranging from 4% to 1300% in the four cases investigated. In all scenarios, water extraction reduced the maximum reservoir pressures approximately 10–20% during injection. In most scenarios, CO2 plume movement could also be influenced through the use of water extraction. The last two aspects may be very beneficial for risk management and monitoring, verification, and accounting practices for all of the CO2 storage projects.

Detailed source term estimation of the atmospheric release for the Fukushima Daiichi Nuclear Power Station accident by coupling simulations of an atmospheric dispersion model with an improved deposition scheme and oceanic dispersion model

Abstract. Temporal variations in the amount of radionuclides released into the atmosphere during the Fukushima Daiichi Nuclear Power Station (FNPS1) accident and their atmospheric and marine dispersion are essential to evaluate the environmental impacts and resultant radiological doses to the public. In this paper, we estimate the detailed atmospheric releases during the accident using a reverse estimation method which calculates the release rates of radionuclides by comparing measurements of air concentration of a radionuclide or its dose rate in the environment with the ones calculated by atmospheric and oceanic transport, dispersion and deposition models. The atmospheric and oceanic models used are WSPEEDI-II (Worldwide version of System for Prediction of Environmental Emergency Dose Information) and SEA-GEARN-FDM (Finite difference oceanic dispersion model), both developed by the authors. A sophisticated deposition scheme, which deals with dry and fog-water depositions, cloud condensation nuclei (CCN) activation, and subsequent wet scavenging due to mixed-phase cloud microphysics (in-cloud scavenging) for radioactive iodine gas (I2 and CH3I) and other particles (CsI, Cs, and Te), was incorporated into WSPEEDI-II to improve the surface deposition calculations. The results revealed that the major releases of radionuclides due to the FNPS1 accident occurred in the following periods during March 2011: the afternoon of 12 March due to the wet venting and hydrogen explosion at Unit 1, midnight of 14 March when the SRV (safety relief valve) was opened three times at Unit 2, the morning and night of 15 March, and the morning of 16 March. According to the simulation results, the highest radioactive contamination areas around FNPS1 were created from 15 to 16 March by complicated interactions among rainfall, plume movements, and the temporal variation of release rates. The simulation by WSPEEDI-II using the new source term reproduced the local and regional patterns of cumulative surface deposition of total 131I and 137Cs and air dose rate obtained by airborne surveys. The new source term was also tested using three atmospheric dispersion models (Modèle Lagrangien de Dispersion de Particules d'ordre zéro: MLDP0, Hybrid Single Particle Lagrangian Integrated Trajectory Model: HYSPLIT, and Met Office's Numerical Atmospheric-dispersion Modelling Environment: NAME) for regional and global calculations, and the calculated results showed good agreement with observed air concentration and surface deposition of 137Cs in eastern Japan.

Transport characteristics of thermal plume driven by turbulent mixing in stairwell

A set of experiments was conducted to study the transport characteristics of thermal plume driven by turbulent mixing in a 1/3 scale stairwell with single opening. The opening location was varied at the stairwell height direction to obtain different air supply conditions. When the thermal plume moves upwardly in the vertical stairwell, the interface between the upper cold layer and the lower hot layer is unstable. The gravitational instability leads to the turbulent mixing in the two layers. The location of the thermal plume front is determined using the temperature increases at different measuring points. Based on the dimensional analysis, the plume front location can be expressed as a function of time and effective gravitational acceleration. The velocity of thermal plume in stairwell is lower than those in hollow shafts, resulting from the block and cooling effects of stair steps. The comparison of the experimental and calculated plume front locations shows good agreement with the maximum error less than 20%. The results could improve the understanding of thermal plume movement driven by turbulent mixing in stairwells.

Plume propagation and Pt film growth during shadow-masked pulsed laser deposition in a buffer Ar gas

Shadow-masked pulsed laser deposition (SMPLD) enables the preparation of films that contain none of the droplets that are normally formed in laser irradiation of the target. The platinum (Pt) film produced by SMPLD was studied using scanning electron microscopy (SEM), atomic force microscopy (AFM), and Rutherford backscattering spectroscopy (RBS) of helium ions. The film thickness distribution across the substrate surface took the shape of a simple crater, and the film thickness on the crated “bottom” (center of the shadow area) was approximately 5 times less than that on the “mound” (edge of the shadow area). Monte Carlo collision (MCC) modeling of the laser plume movement during SMPLD was performed to clarify the role of the mask in the formation of the Pt films. The dynamics of the Pt atoms in the laser plume was studied using the vacuum deposition method through a narrow slit onto a rapidly displaced substrate, augmented by RBS measurements of the deposited film thickness along the substrate movement direction. The ionic flux was specifically measured using an ion probe. MСС simulation allowed the changes in the basic parameters of the deposited atom stream to be evaluated with the use of a mask. Comparison of the experimental and calculated distribution of the Pt film indicated that the best correlation was observed using the interpenetration model of the plume and buffer gas (argon, Ar) accompanied by elastic collisions of Pt atoms with the Ar atoms using the variable hard sphere model. Atomic flux models were utilized to imitate the growth of individual Pt crystals using the kinetic Monte Carlo method. In the SMPLD case, the root mean square roughness of the model crystal surface increased by ∼10% and the concentration of vacancies increased by ∼4% compared with the model crystal obtained by pulsed laser deposition (PLD). The surface topography of the experimental Pt films was defined by the nanocrystal nature of their structure. The use of a mask promoted the growth of relatively large nanocrystals and, thus, an increase in the surface roughness in AFM scans on the submicron scale.

Leachate plume delineation and lithologic profiling using surface resistivity in an open municipal solid waste dumpsite, Sri Lanka

This study presents the use of direct current resistivity techniques (DCRT) for investigation and characterization of leachate-contaminated subsurface environment of an open solid waste dumpsite at Kandy, Sri Lanka. The particular dumpsite has no liner and hence the leachate flows directly to the nearby river via subsurface and surface channels. For the identification of possible subsurface flow paths and the direction of the leachate, DCRT (two-dimensional, three-dimensional and vertical electrical sounding) have been applied. In addition, the physico-chemical parameters such as pH, electrical conductivity (EC), alkalinity, hardness, chloride, chemical oxygen demand (COD) and total organic carbon (TOC) of leachate collected from different points of the solid waste dumping area and leachate drainage channel were analysed. Resistivity data confirmed that the leachate flow is confined to the near surface and no separate plume is observed in the downstream area, which may be due to the contamination distribution in the shallow overburden thickness. The stratigraphy with leachate pockets and leachate plume movements was well demarcated inside the dumpsite via low resistivity zones (1–3 Ωm). The recorded EC, alkalinity, hardness and chloride contents in leachate were averaged as 14.13 mS cm−1, 3236, 2241 and 320 mg L−1, respectively, which confirmed the possible causes for low resistivity values. This study confirms that DCRT can be effectively utilized to assess the subsurface characteristics of the open dumpsites to decide on corridor placement and depth of permeable reactive barriers to reduce the groundwater contamination.

Tracing CO2 leakage into groundwater using carbon and strontium isotopes during a controlled CO2 release field test

During a carbon sequestration field study to simulate the impact of CO2 migration on shallow groundwater chemistry, the isotope composition of dissolved inorganic carbon (δ13CDIC) and dissolved strontium (87Sr/86Sr) were evaluated as tracers. Dissolved CO2 in groundwater was introduced using a closed-loop dipole-style well field situated in a shallow sand-dominated aquifer. Baseline δ13CDIC values, oxygen and hydrogen isotope ratios, and 87Sr/86Sr values of groundwater were established in four monitoring wells (MW-1 to 4) and one up-gradient background well (BG-1) prior to the introduction of dissolved CO2. Baseline groundwater δ13CDIC-PDB, oxygen (δ18OSMOW) and hydrogen (δDSMOW) stable isotope values averaged −17, −4.1 and −19.5‰, respectively. Groundwater 87Sr/86Sr baseline values averaged 0.70840 at MW-3 and 0.70818 at MW-2. Arrival of the dissolved CO2 plume at the monitoring wells is modeled using a 1-D analytical equation, which yields breakthrough curves with flow velocities that are consistent with prior numerical modeling estimates. The δ13CDIC-PDB rose to an average steady-state value of 0.16±0.3‰ during the test; δ18O and δD of water did not change from their baseline values. 87Sr/86Sr dropped sharply by 0.00022 at MW-3 and 0.00005 at MW-2 in the first two weeks after plume arrival at the wells, and then slowly increased toward baseline values, correlating with the behavior of dissolved Na, K, Ca, Sr and Si. Carbonate dissolution and desorption from organic matter and Fe-bearing phases at the low-pH plume front is the likely mechanism producing this behavior. The δ13CDIC and the 87Sr/86Sr of dissolved strontium served as excellent tracers of plume movement during this experiment.

Fundamental Analysis of the Impacts Relative Permeability has on $$\hbox {CO}_{2}$$ CO 2 Saturation Distribution and Phase Behavior

A critical aspect of geologic carbon storage, a carbon-emissions reduction method under extensive review and testing, is the ability to simulate multiphase \(\hbox {CO}_{2}\) flow and transport. Relative permeability is a flow parameter particularly critical for accurate forecasting of multiphase behavior of \(\hbox {CO}_{2}\) in the subsurface. Specifically, for clastic formations, small-scale (cm) bedding planes can have a significant impact on multiphase \(\hbox {CO}_{2}\)-brine fluid flow, depending on the relative permeability relationship assumed. Such small-scale differences in permeability attributable to individual bedding planes may also have a substantial impact on predicted \(\hbox {CO}_{2}\) storage capacity and long-term plume migration behavior. A major goal of this study was to evaluate and calibrate relative permeability models against experimental data to improve simulation capability. We analyzed previously published laboratory-scale measurements of relative permeability of Berea sandstone, and developed a corresponding 3-D simulation model calibrated with those measurements. The simulation model was created in the TOUGHREACT reactive transport simulator, and we elucidated best-fit relative permeability formulations to match the experimental data. Among several functions evaluated, best-fit between simulation results and experimental observations was achieved with a calibrated van Genuchten–Mualem formulation. To extend the analysis to a more heterogeneous medium, we applied the best-fit relative permeability formulations to a new model of a small-scale Navajo Sandstone reservoir. The model was one cubic meter in size, with eight individual lithofacies of differing permeability, gridded to mimic small-scale bedding planes. For this model we assumed that each lithofacies exhibits its own random permeability field. We then evaluated four different relative permeability functions to quantify their impact on flow results for each model, with all other parameters maintained uniform and constant. Results of this analysis suggest that \(\hbox {CO}_{2}\) plume movement and behavior are significantly dependent on the specific relative permeability formulation assigned, including the assumed irreducible saturation values of \(\hbox {CO}_{2}\) and brine. More specifically, different relative permeability formulations translate to significant differences in \(\hbox {CO}_{2}\) saturation profile and phase behavior.

Time series analysis of contaminant transport in the subsurface: Applications to conservative tracer and engineered nanomaterials

Accurately predicting the transport of contaminants in the field is subject to multiple sources of uncertainty due to the variability of geological settings, the complexity of field measurements, and the scarcity of data. Such uncertainties can be amplified when modeling some emerging contaminants, such as engineered nanomaterials, when a fundamental understanding of their fate and transport is lacking. Typical field work includes collecting concentration at a certain location for an extended period of time, or measuring the movement of plume for an extended period time, which would result in a time series of observation data. This work presents an effort to evaluate the possibility of applying time series analysis, particularly, autoregressive integrated moving average (ARIMA) models, to forecast contaminant transport and distribution in the subsurface environment. ARIMA modeling was first assessed in terms of its capability to forecast tracer transport at two field sites, which had different levels of heterogeneity. After that, this study evaluated the applicability of ARIMA modeling to predict the transport of engineered nanomaterials at field sites, including field measured data of nanoscale zero valent iron and (nZVI) and numerically generated data for the transport of nano-fullerene aggregates (nC60). This proof-of-concept effort demonstrates the possibility of applying ARIMA to predict the contaminant transport in the subsurface environment. Like many other statistical models, ARIMA modeling is only descriptive and not explanatory. The limitation and the challenge associated with applying ARIMA modeling to contaminant transport in the subsurface are also discussed.

The use of Numerical Weather Prediction and a Lagrangian transport (NAME-III) and dispersion (ASHFALL) models to explain patterns of observed ash deposition and dispersion following the August 2012 Te Maari, New Zealand eruption

The August 6, 2012 Te Maari, New Zealand eruption produced a very small ash-dominated plume (~230,000m3, 8–10km high) that was rapidly and widely dispersed, covering 1600km2 within an hour. This paper documents for the August 6, 2012 Te Maari eruption the upper level (troposphere) plume movement based on ash-detection algorithms applied to IR satellite imagery. It also presents the distribution of airborne ash and wind-influenced ashfall as determined by NAME-III aerial dispersion modelling using observed particle characteristics and grain size distribution measurements (that are also presented) and compares the ashfall with observations.The upper level (troposphere) ash movement was also evaluated from ash-detection algorithms, applied to infra-red satellite imagery and the resulting distributions were compared to those forecast by the numerical dispersion models. Forecasts of upper level ash-dispersion patterns explained the satellite imagery observations well, predicting the correct altitudes when using plausible ash size distributions and release levels. Patterns in proximal ashfall could only be partly explained by aerial dispersal of large particles released at low altitudes in the eruption column. The extreme distal (100–150km away) observed ashfall distributions also cannot be fully explained by NAME-III when using: reasonably prescribed initial particle size distributions, eruption column height, eruption timing, well forecast winds, and dry sedimentation processes. Aggregation and ice nucleation effects (observed in deposits) were not included in the ash dispersion model, but appear as a plausible mechanism to account for the observed fraction of wind dispersed ash particles <30μm deposited but not captured by the models.