C. Gable - Academia.edu (original) (raw)

Papers by C. Gable

Computing and Visualization in Science, 2012

ABSTRACT The Mount Simon and Lower Knox Group Formations within the Illinois Basin, USA, are bein... more ABSTRACT The Mount Simon and Lower Knox Group Formations within the Illinois Basin, USA, are being considered as targets for carbon dioxide (CO 2) storage. Two main concerns related to the subsurface storage process are potential leakage of CO 2 from the storage formation to the atmosphere and possible migration of CO 2 or displaced brine into underground sources of drinking water. In this study we use a numerical model to represent the migration of both CO 2 and brine in the Mount Simon Sandstone and two overlying aquifers, the shallowest of which is considered a potential source of drinking water. A vertically-integrated approach is used to model the fluid flow, leading to a stack of two-dimensional subdomains which are connected by leakage through the aquitards which separate the aquifers. Each formation is discretized into 12,103 grid cells, each 5 × 5 km, and permeability and porosity vary spatially. Two vertical refinements are used for the Mount Simon Sandstone: the first represents the Mount Simon as a single layer, while the second subdivides the formation into subunits within the formation that have varying petrophysical properties. The locations and injection rates of the hypothetical injection operations are based on existing sources of CO 2 associated with power generation, ethanol production, and oil and gas refineries. A total of 250.5 million metric tons are injected at 118 sites. The injection operations are assumed to continue for 50 years. Results indicate the maximum radial extent of the CO 2 plume increased from 40 to 50 km between the single layer and multi-layer representations of the Mount Simon. Maximum average pore pressures reached 8.6 MPa and the pressure envelop extended as much as 100 km from the injection wells with significant well-well pressure interference patterns. The maximum well head pressure exceeded the fracture pressure in some cases suggesting more wells may be needed at some of the lower permeability injection sites. Brine leakage into overlying shallower units was not significant.

Geofluids, 2012

Fault intersections are the locus of hot spring activity and Carlin-type gold mineralization with... more Fault intersections are the locus of hot spring activity and Carlin-type gold mineralization within the Basin and Range, USA. Analytical and numerical solutions to Stokes equation suggest that peak fluid velocities at fault intersections increase between 20% and 47% when fracture apertures have identical widths but increase by only about 1% and 8% when aperture widths vary by a factor of 2. This suggests that fault zone intersections must have enlarged apertures. Three-dimensional finite element models that consider intersecting 10-to 20-m wide fault planes resulted in hot spring activity being preferentially located at fault zone intersections when fault zones were assigned identical permeabilities. We found that the onset of convection at the intersections of the fault zones occurred in our hydrothermal model over a narrow permeability range between 5 • 10)13 and 7 • 10)13 m 2. Relatively high vertical fluid velocities (0.3-3 m year)1) extended away from the fault intersections for about 0.5-1.5 km. For the boundary conditions and fault plane dimensions used, peak discharge temperatures of 112°C at the water table occurred with an intermediate fault zone permeability of 5 • 10)13 m 2. When fault plane permeability differed by a factor of 2 or more, the locus of hot spring activity shifted away from the intersections. However, increasing the permeability at the core of the fault plane intersection by 40% shifted the discharge back to the intersections. When aquifer units were assigned a permeability value equal to those of the fault planes, convective rolls developed that extend about 3 km laterally along the fault plane and into the adjacent aquifer.

ABSTRACT We are investigating the plumbing of the Coso geothermal system and the nearby Coso Hot ... more ABSTRACT We are investigating the plumbing of the Coso geothermal system and the nearby Coso Hot Springs using finite element models of single-phase, variable-density fluid flow, conductive-convective heat transfer, fluid-rock isotope exchange, and groundwater residence times. Using detailed seismic reflection data and geologic mapping, we constructed a regional cross-sectional model that extends laterally from the Sierra Nevada to Wildhorse Mesa, west of the Argus Range. The base of the model terminates at the brittle-ductile transition zone. A sensitivity study was conducted using the model to explore the interaction between local and mountain front recharge, the effects of spatial variations in heat flow, and the role of permeable faults in controlling fluid circulation patterns. The model is constrained by present day bore hole temperature surveys, fluid inclusion temperatures, fluid-rock isotopic alteration patterns, and hot spring activity. While the results are non-unique, the analysis permits us to bracket the likely ranges of permeabilities and heat flow conditions that are consistent with observed data. Our findings suggest that active faults and seismogenic zones in and around the Coso geothermal area have much higher permeability and reactive surface areas than far field crustal rocks such as those in the Sierra Nevada. The Coso Wash fault zone must extend down to brittle- ductile transition zone depths of about 4 km in order for modeled results to match the observed hot spring activity.

Geochemistry, Geophysics, Geosystems, 2014

Multiple late Pleistocene glaciations that extended onto the continental shelf offshore Massachus... more Multiple late Pleistocene glaciations that extended onto the continental shelf offshore Massachusetts, USA, may have emplaced as much as 100 km 3 of freshwater (salinity <5 ppt) in continental shelf sediments. To estimate the volume and extent of offshore freshwater, we developed a three-dimensional, variable-density model that couples fluid flow and heat and solute transport for the continental shelf offshore Massachusetts. The stratigraphy for our model is based on high-resolution, multichannel seismic data. The model incorporates the last 3 Ma of climate history by prescribing boundary conditions of sea level change and ice sheet extent and thickness. We incorporate new estimates of the maximum extent of a late Pleistocene ice sheet to near the shelf-slope break. Model results indicate that this late Pleistocene ice sheet was responsible for much of the emplaced freshwater. We predict that the current freshwater distribution may reach depths up to 500 meters below sea level and up to 30 km beyond Martha's Vineyard. The freshwater distribution is strongly dependent on the three-dimensional stratigraphy and ice sheet history. Our predictions improve our understanding of the distribution of offshore freshwater, a potential nonrenewable resource for coastal communities along recently glaciated margins.

X3D is the grid generation system that we use at Los Alamos and is designed for multimaterial, ti... more X3D is the grid generation system that we use at Los Alamos and is designed for multimaterial, time-dependent, 3D hybrid grids that are either statically adapted or evolved in time. Its capabilities include static and dynamic grids, hybrid grids, managing colliding ...

Geofluids, 2014

ABSTRACT The pollen 14C age and oxygen isotopic composition of siliceous sinter deposits from the... more ABSTRACT The pollen 14C age and oxygen isotopic composition of siliceous sinter deposits from the former Beowawe geyser field reveal evidence of two hydrothermal discharge events that followed relatively low-magnitude (<M5) earthquakes of Holocene and late Pleistocene age along the Malpais fault zone in Whirlwind Valley, Nevada, USA. The observed 20‰ trend of decreasing d18O over about a 5000-to-7000-year period following each earthquake is consistent with a fault-controlled groundwater flow system that, following initial discharge of deep and hot groundwater, contains increasing amounts of cool meteoric water through time. Model simulations of this hydrothermal system can only match trends in the isotope data if we include a thousand-fold increase in fault permeability (from <10�14 m2 to >10�11 m2 ) following each earthquake. However, the timescale for onset of thermal convection implied by an overturned temperature profile in a geothermal well 300 m from the Malpais fault is much shorter: 200–1000 years. We speculate that individual segments of the Malpais fault become clogged on shorter timescales and that upward flow of groundwater subsequently follows new routes to the surface. Key words: fault, hydrothermal, oxygen isotope, permeability, sinter

Stochastic Environmental Research and Risk Assessment, 2015

Understanding the heterogeneity arising from the complex architecture of sedimentary sequences in... more Understanding the heterogeneity arising from the complex architecture of sedimentary sequences in alluvial fans is challenging. This paper develops a statistical inverse framework in a multizone transition probability approach for characterizing the heterogeneity in alluvial fans. An analytical solution of the transition probability matrix is used to define the statistical relationships among different hydrofacies and their mean lengths, integral scales, and volumetric proportions. A statistical inversion is conducted to identify the multi-zone transition probability models and estimate the optimal statistical parameters using the modified Gauss-Newton-Levenberg-Marquardt method. The Jacobian matrix is computed by the sensitivity equation method, which results in an accurate inverse solution with quantification of parameter uncertainty. We use the Chaobai River alluvial fan in the Beijing Plain, China, as an example for elucidating the methodology of alluvial fan characterization. The alluvial fan is divided into three sediment zones. In each zone, the explicit mathematical formulations of the transition probability models are constructed with optimized different integral scales and volumetric proportions. The hydrofacies distributions in the three zones are simulated sequentially by the multi-zone transition probability-based indicator simulations. The result of this study provides the heterogeneous structure of the alluvial fan for further study of flow and transport simulations.

Clay and granitic media are potential host media for future repositories for used nuclear fuel. T... more Clay and granitic media are potential host media for future repositories for used nuclear fuel. This report addresses the representation of flow in these two media within numerical process models.

This report was prepared as an account of work sponsored by an agency of the United States Govern... more This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

Journal of Geophysical Research, 2003

We present a numerical model of the subducting lithosphere that provides an alternative explanati... more We present a numerical model of the subducting lithosphere that provides an alternative explanation for stresses causing deep earthquakes. Our model lithosphere is composed of alpha olivine, beta spinel, gamma spinel, and perovskite + magnesiowüstite. The heat conduction equation is solved to determine temperature conditions in the slab and to locate the equilibrium phase transformations in pressure-temperature space. Volumetric strains in the subducting lithosphere are calculated from the density of individual phases and from the heat released or consumed in the phase changes. These strains are used as sources of stress in the subducting lithosphere. Dislocation creep and Peierls stress creep laws are included in the viscoelastic rheology. Volumetric reductions due to equilibrium phase transformations cause high shear stress in the transition zone because of the variable viscosity inside the subducting slab. Aspects of the model shear stresses are in agreement with observations of high seismic activity in the Tonga-Wadati Benioff zone. Compression is oriented along the dip of the slab, and extension is oriented in the plane perpendicular to the compression axis. Since our model stresses agree with the seismic observations, and because the model stresses are larger than those caused by buoyancy forces, our model provides a possible explanation of stresses causing deep earthquakes. Also, our model does not need metastability of olivine to explain the occurrence of high shear stress in the transition zone.

International Journal of Greenhouse Gas Control, 2010

Idealized, basin-scale sharp-interface models of CO 2 injection were constructed for the Illinois... more Idealized, basin-scale sharp-interface models of CO 2 injection were constructed for the Illinois basin. Porosity and permeability were decreased with depth within the Mount Simon Formation. Eau Claire confining unit porosity and permeability were kept fixed. We used 726 injection wells located near 42 power plants to deliver 80 million metric tons of CO 2 /year. After 100 years of continuous injection, deviatoric fluid pressures varied between 5.6 and 18 MPa across central and southern part of the Illinois basin. Maximum deviatoric pressure reached about 50% of lithostatic levels to the south. The pressure disturbance (>0.03 MPa) propagated 10-25 km away from the injection wells resulting in significant well-well pressure interference. These findings are consistent with single-phase analytical solutions of injection. The radial footprint of the CO 2 plume at each well was only 0.5-2 km after 100 years of injection. Net lateral brine displacement was insignificant due to increasing radial distance from injection well and leakage across the Eau Claire confining unit. On geologic time scales CO 2 would migrate northward at a rate of about 6 m/1000 years. Because of paleo-seismic events in this region (M5.5-M7.5), care should be taken to avoid high pore pressures in the southern Illinois basin.

Geology, 2011

Abstract This study assesses the relative importance of deeply circulating meteoric water and dir... more Abstract This study assesses the relative importance of deeply circulating meteoric water and direct mantle fluid inputs on near-surface 3 He/4 He anomalies reported at the Coso and Beowawe geothermal fields of the western United States. The depth of meteoric fluid ...

Well bores have long shown that relatively fresh groundwater exists far offshore beneath the Atla... more Well bores have long shown that relatively fresh groundwater exists far offshore beneath the Atlantic continental shelves of North and South America. This freshwater was emplaced during Pleistocene sea-level low stands when the shelf was exposed to meteoric recharge and parts were over-run by the Laurentide Ice Sheet. Details of the emplacement mechanism of the fresh water remain poorly understood.

Based on the regional hydrogeology and the stratigraphy beneath the Los Alamos National Laborator... more Based on the regional hydrogeology and the stratigraphy beneath the Los Alamos National Laboratory (LANL) site, New Mexico (USA), a site-scale groundwater model has been built with more than 20 stratified hydrofa- cies. A stepwise inverse method was developed to estimate permeabilities for these hydrofacies by coupling observation data from different sources and at various spatial scales including single-well test,