Time filter

Source Type

Plampin M.R.,Colorado School of Mines | Sakaki T.,Colorado School of Mines | Porter M.L.,Earth and Environmental science DivisionLos Alamos National LaboratoryLos Alamos | Pawar R.J.,Earth and Environmental science DivisionLos Alamos National LaboratoryLos Alamos | Illangasekare T.H.,Colorado School of Mines
Water Resources Research | Year: 2014

A primary concern for geologic carbon storage is the potential for leakage of stored carbon dioxide (CO2) into the shallow subsurface where it could degrade the quality of groundwater and surface water. In order to predict and mitigate the potentially negative impacts of CO2 leakage, it is important to understand the physical processes that CO2 will undergo as it moves through naturally heterogeneous porous media formations. Previous studies have shown that heterogeneity can enhance the evolution of gas phase CO2 in some cases, but the conditions under which this occurs have not yet been quantitatively defined, nor tested through laboratory experiments. This study quantitatively investigates the effects of geologic heterogeneity on the process of gas phase CO2 evolution in shallow aquifers through an extensive set of experiments conducted in a column that was packed with layers of various test sands. Soil moisture sensors were utilized to observe the formation of gas phase near the porous media interfaces. Results indicate that the conditions under which heterogeneity controls gas phase evolution can be successfully predicted through analysis of simple parameters, including the dissolved CO2 concentration in the flowing water, the distance between the heterogeneity and the leakage location, and some fundamental properties of the porous media. Results also show that interfaces where a less permeable material overlies a more permeable material affect gas phase evolution more significantly than interfaces with the opposite layering. © 2014. American Geophysical Union. All Rights Reserved.


Dai Z.,Earth and Environmental science DivisionLos Alamos National LaboratoryLos Alamos
Water Resources Research | Year: 2015

This series of papers addresses the transport of reactive solutes in groundwater. In part 1, the time-dependent effective retardation factor, R∼eff(t), of reactive solutes undergoing equilibrium sorption is linked to hierarchical stratal architecture using a Lagrangian-based transport model. The model is based on hierarchical expressions of the spatial covariance of the log distribution coefficient, Ξ=ln><(Kd), and the spatial cross covariance between Ξ and the log permeability, Y=ln><(k). The spatial correlation structure in these covariance expressions is the probability of transitioning across strata types of different scales, and they are parameterized by independent and quantifiable physical attributes of sedimentary architecture including univariate statistics for Y, Ξ, and the proportions and lengths of facies. Nothing is assumed about Y- Ξ point correlation; it is allowed to differ by facies type. The duration of the time-dependent change in R∼eff(t) is a function of the effective ranges of the cross-transition probability structures (i.e., the ranges of indicator correlation structures) for each scale of stratal architecture. The plume velocity and the effective retardation stabilize at a large-time limit after the plume centroid has traveled a distance that encompasses the effective ranges of these cross-transition probability structures. The well-documented perchloroethene (PCE) tracer test at the Borden research site is used to illustrate the model. The model gives a viable explanation for the observed PCE plume deceleration, and thus the observed R∼eff(t) can be explained by the process of linear equilibrium sorption and the heterogeneity in k and Kd. In part 2 [Soltanian et al., ], reactive plume dispersion, as quantified by the particle displacement variance is linked to stratal architecture using a Lagrangian-based transport model. © 2015. American Geophysical Union.


Birdsell D.T.,Environmental and Architectural EngineeringUniversity of ColoradoBoulder | Rajaram H.,Environmental and Architectural EngineeringUniversity of ColoradoBoulder | Viswanathan H.S.,Earth and Environmental science DivisionLos Alamos National LaboratoryLos Alamos
Water Resources Research | Year: 2015

Understanding the transport of hydraulic fracturing (HF) fluid that is injected into the deep subsurface for shale gas extraction is important to ensure that shallow drinking water aquifers are not contaminated. Topographically driven flow, overpressured shale reservoirs, permeable pathways such as faults or leaky wellbores, the increased formation pressure due to HF fluid injection, and the density contrast of the HF fluid to the surrounding brine can encourage upward HF fluid migration. In contrast, the very low shale permeability and capillary imbibition of water into partially saturated shale may sequester much of the HF fluid, and well production will remove HF fluid from the subsurface. We review the literature on important aspects of HF fluid migration. Single-phase flow and transport simulations are performed to quantify how much HF fluid is removed via the wellbore with flowback and produced water, how much reaches overlying aquifers, and how much is permanently sequestered by capillary imbibition, which is treated as a sink term based on a semianalytical, one-dimensional solution for two-phase flow. These simulations include all of the important aspects of HF fluid migration identified in the literature review and are performed in five stages to faithfully represent the typical operation of a hydraulically fractured well. No fracturing fluid reaches the aquifer without a permeable pathway. In the presence of a permeable pathway, 10 times more fracturing fluid reaches the aquifer if well production and capillary imbibition are not included in the model. © 2015. American Geophysical Union. All Rights Reserved.


Chen L.,Los Alamos National Laboratory | Kang Q.,Earth and Environmental science DivisionLos Alamos National LaboratoryLos Alamos | Viswanathan H.S.,Earth and Environmental science DivisionLos Alamos National LaboratoryLos Alamos | Tao W.-Q.,Xi'an Jiaotong University
Water Resources Research | Year: 2014

A pore-scale numerical model for reactive transport processes based on the Lattice Boltzmann method is used to study the dissolution-induced changes in hydrologic properties of a fractured medium and a porous medium. The solid phase of both media consists of two minerals, and a structure reconstruction method called quartet structure generation set is employed to generate the distributions of both minerals. Emphasis is put on the effects of undissolved minerals on the changes of permeability and porosity under different Peclet and Damkohler numbers. The simulation results show porous layers formed by the undissolved mineral remain behind the dissolution reaction front. Due to the large flow resistance in these porous layers, the permeability increases very slowly or even remains at a small value although the porosity increases by a large amount. Besides, due to the heterogeneous characteristic of the dissolution, the chemical, mechanical and hydraulic apertures are very different from each other. Further, simulations in complex porous structures demonstrate that the existence of the porous layers of the nonreactive mineral suppresses the wormholing phenomena observed in the dissolution of mono-mineralic rocks. © 2014. American Geophysical Union.


Hyman J.D.,Center for Nonlinear Studies | Painter S.L.,New Mexico United States | Viswanathan H.,Earth and Environmental science DivisionLos Alamos National LaboratoryLos Alamos | Makedonska N.,Earth and Environmental science DivisionLos Alamos National LaboratoryLos Alamos | Karra S.,Earth and Environmental science DivisionLos Alamos National LaboratoryLos Alamos
Water Resources Research | Year: 2015

We investigate how the choice of injection mode impacts transport properties in kilometer-scale three-dimensional discrete fracture networks (DFN). The choice of injection mode, resident and flux-weighted, is designed to mimic different physical phenomena. It has been hypothesized that solute plumes injected under resident conditions evolve to behave similarly to solutes injected under flux-weighted conditions. Previously, computational limitations have prohibited the large-scale simulations required to investigate this hypothesis. We investigate this hypothesis by using a high-performance DFN suite, dfnWorks, to simulate flow in kilometer-scale three-dimensional DFNs based on fractured granite at the Forsmark site in Sweden, and adopt a Lagrangian approach to simulate transport therein. Results show that after traveling through a pre-equilibrium region, both injection methods exhibit linear scaling of the first moment of travel time and power law scaling of the breakthrough curve with similar exponents, slightly larger than 2. The physical mechanisms behind this evolution appear to be the combination of in-network channeling of mass into larger fractures, which offer reduced resistance to flow, and in-fracture channeling, which results from the topology of the DFN. © 2015. American Geophysical Union. All Rights Reserved.

Loading Earth and Environmental science DivisionLos Alamos National LaboratoryLos Alamos collaborators
Loading Earth and Environmental science DivisionLos Alamos National LaboratoryLos Alamos collaborators