Geologic Framework Model Research Articles

Assessing the Accuracy of a Borehole-Controlled P-Wave Velocity Model of Yucca Flat, Nevada Using Large-N Seismic Data

ABSTRACT With geologic data from over 950 boreholes, Yucca Flat basin, residing on the Nevada National Security Site, has excellent borehole control on stratigraphy. These data were used to create a Geologic Framework Model (GFM) of the basin. Of these boreholes, 188 have corresponding downhole seismic survey data, which were used to determine average P-wave velocities of the geologic units and create a GFM seismostratigraphic model (GFM-SS). With the acquisition of six new active-source large-N datasets in Yucca Flat, we can now quantitatively assess the accuracy of the GFM-SS previously controlled only by borehole data. For each of the six datasets, we subset the GFM to the region of interest and create a forward model of P-wave travel times for the GFM-SS given the large-N source-receiver geometries. We first made trial-and-error adjustments to the unit velocities (while keeping the layer geometry intact) to improve the travel-time residuals. We then implemented a simulated annealing approach to find the optimal velocity model for each dataset. Our results indicate that the borehole-controlled model overestimates alluvium velocities across Yucca Flat. This result persists even when we make smaller GFM-SS models that are local to individual large-N experiments. We hypothesize that this result is a combination of shorter ray paths and the resulting lack of interaction with large-scale features (such as faults), as well as less attenuation of high frequencies in the borehole data. Both the current GFM-SS and the updated model based on median velocities that we present here overgeneralize local unit velocities, which can be quite heterogeneous in Yucca Flat.

Geophysical and geological surveys to understand the hydrogeological behavior in an outcrop area of the Guarani Aquifer System, in Brazil

In some Brazilian states, after the long period of drought in the years 2014 to 2015, the issue of water crises became the focus of several studies. Some of these studies propose the use of groundwater to avoid water crises. However, many of these do not understand or ignore the hydrological processes of aquifer recharge and discharge. Understanding the recharge and discharge processes is essential to prevent problems related to aquifers and better understand the exchange relationships between surface and underground reservoirs. Geophysical applications are used to study these hydrological processes of recharge and discharge, however there is a deficit regarding the use of the Electrorestivity method in this type of study. The present work delimited an area close to the escarpment of the Basaltic Cuesta front in the municipality of Ipeúna (SP). The objectives were to understand the recharge and discharge processes using the Electrical Resistivity Tomography (ERT) and a stratigraphic survey. The chosen area is in an outcrop area of the Guarani Aquifer System (GAS), a place known to be important in the recharge of this transboundary aquifer. The stratigraphic survey was carried out by walking along the access road to the study area. In the geophysical survey, 10 parallel lines of electrical resistivity tomography (ERT) were performed in Schlumberger array. The measured resistivity values ranged between 5000 Ω m and 20 Ω m. Data collected in the field were processed and represented in two-dimensional and three-dimensional logarithmic models. Through the correlation between stratigraphy and 2D models, it was possible to locate the porous and fractured aquifers, as well as to relate the resistivity values with the rocks present in the area. The 3D model provided a better visualization of the electrical resistivity values at different depths in the study area. In this way, it was possible to delimit the presence of water in the geological framework. The presence of water inside a large sandstone lens flowing towards the Cuesta front was identified. The geophysical and stratigraphy surveys provided information for the generation of a geological framework model, its relationship with groundwater flow and hydrological processes. The work also reduces the gap of geophysical studies in Guarani Aquifer System and the use of electrical resistivity tomography to understand the hydrological processes of aquifers.

Interactive web mapping tools and custom subsurface cross-sections for interdisciplinary geologic investigation

Using Python-based geospatial analytics, open-source web mapping technologies, geophysical data models, and subsurface stratigraphy models from the Regional Geology Geologic Framework Model database assembled by Los Alamos National Laboratory, we developed a suite of web-based geologic investigation tools to identify and understand subsurface structures and geophysical properties concerning salt and shale formations within the contiguous United States. Coupled with a web map interface, these tools allow for the interactive visualization of various geologic data and demonstrate the ability to quickly generate custom subsurface cross-sections, borehole charts, and diagrams for azimuthal orientation data. These capabilities were developed for stakeholder and researcher use to facilitate informed decision making for spent nuclear waste disposition. However, these capabilities provide a flexible model for a variety of subsurface investigation needs, and we have demonstrated this flexibility by adapting these tools to meet visualization needs for various subsurface models within a web-based platform.

Stratigraphic identification with airborne electromagnetic methods at the Hanford Site, Washington

Stratigraphic units can influence the fate and transport of subsurface contaminants within groundwater. Units having coarse-grained sediments act as preferential flow pathways, and therefore can accelerate the transport of contaminants to reach human and ecological receptors. At legacy waste sites, detailed knowledge of subsurface stratigraphy can be used for effective monitoring and remediation planning to help minimize risk to human health and the environment. Airborne electromagnetic (AEM) methods can non-invasively provide information on kilometer-scale or larger subsurface stratigraphic features and fill informational gaps in directly sampled data from sparsely located boreholes. In this paper, we present inversion results of a 412 line-km frequency-domain AEM survey to delineate subsurface stratigraphic features at the Hanford Site, located in southeastern Washington State. The inversion was performed using a massively parallel 3D electromagnetic modeling and inversion code, where the modeling is based on solving frequency-domain Maxwell's equations using an unstructured-mesh finite-element method and the inversion employs a Gauss-Newton optimization scheme. The results are compared to an underlying geologic framework model (GFM), built by interpolating contact depths of stratigraphic units interpreted from site borehole datasets. In areas with good borehole coverage, the inversion results show a good match with the GFM to a depth of about 60 m. Outside of these areas, the inversion results exhibit inconsistencies from the assumptions made to create the GFM, demonstrating that the AEM survey results can be used to improve the understanding of the geological conceptual model.

Insights into the hydrogeological framework of the NW Himalayan Karewas (India)

Karewas which represent the Quarternary sediments deposited in fluvio-lacustrine/fluvio-glacial environment and peripherally surround the valley of the Jhelum river basin in India are highly devoid of surface water resources. The present study is an investigation of the subsurface regime of watersheds of Jhelum basin, encompassing alluvial and Karewa (fluvio-lacustrine) sediments using various software-based techniques with an aim to understand its groundwater scenario. Geological and hydrogeological framework models were developed to infer vertical and horizontal extent of aquifers. The models predict multiple fine sand aquifers in the alluvial sediments, 0.3 to 48 m thick, encountered at 3 to 10 m below the ground level (m bgl); major potential aquifer of 10 to 50 m thickness in Upper Karewa sediments at a depth of 25 to 35 m bgl and about 20 m thick aquifer in Lower Karewa sediments. Water table location obtained by geospatial (stochastic and deterministic) interpolation of static water levels reveals shallow water table at 0.3 to 10 m bgl within almost the entire alluvium region, deepening to 30 m bgl within the Karewa formations. The confining heads vary from a few meters below the ground surface to a few meters above it within alluvium, and much higher within the Karewas attributable to the location of recharge zones within the tall mountains bordering the study area. The study provides a framework for numerical groundwater modelling of the region. The methodology outlined in this study can be applied to diverse geological environments across local or regional scales to understand the hydrogeological conditions therein.

Seismic Velocity Modeling in the Northwest Pearl River Mouth Basin, South China Sea

Accurate seismic velocity can determine the depth, dip angle and location of the stratum, and study the properties of rocks and pore fluid, such as rock density, reservoir location, gas hydrate anomaly and deep tectonic characteristics. The South China Sea (SCS) has special tectonic location and complex evolution history, which has always been the focus of geologists and geophysicists. At the same time, the SCS is rich in oil/gas resources, and is one of the four major marine oil-gas accumulation zones in the world. In this paper, three-dimensional velocity modeling was carried out in northwest Pearl River Mouth Basin of the SCS based on the three-dimensional geological framework model. Minimum Curvature Interpolation was used in the three-dimensional velocity modeling. Results showed that the three-dimensional velocity model can visually display sedimentary boundary and basin basement. The geological framework model makes the lateral velocity change of strata more in line with the actual geological structure. Considering the key role of the underground layer velocity in the exploration of oil, gas, hydrate and lower-crustal structure, it will be of great scientific and resources significance to carry out the three-dimensional velocity modeling research in the SCS.

Effect of Random 3D Correlated Velocity Perturbations on Numerical Modeling of Ground Motion from the Source Physics Experiment

ABSTRACTExplosions are traditionally discriminated from earthquakes, using the relative amplitude of compressional and shear waves at regional and teleseismic distances known as the P/S discriminant. Pyle and Walter (2019) showed this technique to be less robust at shorter distances, in detecting small-magnitude earthquakes and low-yield explosions. The disparity is largely due to ground motion from small, shallow sources being significantly impacted by near-surface structural complexities. To understand the implications of wave propagation effects in generation of shear motion and P/S ratio during underground chemical explosions, we performed simulations of the Source Physics Experiment (SPE) chemical explosions using 1D and 3D velocity models of the Yucca Flat basin. All simulations used isotropic point sources in the frequency range 0–5 Hz. We isolate the effect of large-scale geological structure and small-scale variability at shallow depth (<5 km), using a regional 3D geologic framework model (GFM) and the GFM-R model derived from the GFM, by adding correlated stochastic velocity perturbations. A parametric study of effects of small-scale velocity variations on wave propagation, computed using a reference 1D velocity model with stochastic perturbations, shows that the correlation length and depth of stochastic perturbations significantly impact wave scattering, near-surface wave conversions, and shear-wave generation. Comparisons of recorded and simulated waveforms for the SPE-5 explosion, using 3D velocity models, demonstrate that the shallow structure of the Yucca Flat basin contributes to generation of observed shear motion. The inclusion of 3D wave scattering, simulated by small-scale velocity perturbations in the 3D model, improves the fit between the simulated and recorded waveforms. In addition, a relatively low intrinsic attenuation, combined with small-scale velocity variations in our models, can confirm the observed wave trapping and its effect on duration of coda waves and the spatial variation of P/S ratio at basin sites.

Physically Based Estimation of Rainfall Thresholds Triggering Shallow Landslides in Volcanic Slopes of Southern Italy

On the 4th and 5th of March 2005, about 100 rainfall-induced landslides occurred along volcanic slopes of Camaldoli Hill in Naples, Italy. These started as soil slips in the upper substratum of incoherent and welded volcaniclastic deposits, then evolved downslope according to debris avalanche and debris flow mechanisms. This specific case of slope instability on complex volcaniclastic deposits remains poorly characterized and understood, although similar shallow landsliding phenomena have largely been studied in other peri-volcanic areas of the Campania region underlain by carbonate bedrock. Considering the landslide hazard in this urbanized area, this study focused on quantitatively advancing the understanding of the predisposing factors and hydrological conditions contributing to the initial landslide triggering. Borehole drilling, trial pits, dynamic penetrometer tests, topographic surveys, and infiltration tests were conducted on a slope sector of Camaldoli Hill to develop a geological framework model. Undisturbed soil samples were collected for laboratory testing to further characterize hydraulic and geotechnical properties of the soil units identified. In situ soil pressure head monitoring probes were also installed. A numerical model of two-dimensional variably saturated subsurface water flow was parameterized for the monitored hillslope using field and laboratory data. Based on the observed soil pressure head dynamics, the model was calibrated by adjusting the evapotranspiration parameters. This physically based hydrologic model was combined with an infinite-slope stability analysis to reconstruct the critical unsaturated/saturated conditions leading to slope failure. This coupled hydromechanical numerical model was then used to determine intensity–duration (I-D) thresholds for landslide initiation over a range of plausible rainfall intensities and topographic slope angles for the region. The proposed approach can be conceived as a practicable method for defining a warning criterion in urbanized areas threatened by rainfall-induced shallow landslides, given the unavailability of a consistent inventory of past landslide events that prevents a rigorous empirical analysis.

Co‐optimization of CO2‐EOR and storage processes in mature oil reservoirs

AbstractThis paper presents an optimization methodology for CO2enhanced oil recovery in partially depleted reservoirs. A field‐scale compositional reservoir flow model was developed for assessing the performance history of an active CO2flood and for optimizing both oil production and CO2storage in the Farnsworth Unit (FWU), Ochiltree County, Texas. A geological framework model constructed from geophysical, geological, and engineering data acquired from the FWU was the basis for all reservoir simulations and the optimization method. An equation of state was calibrated with laboratory fluid analyses and subsequently used to predict the thermodynamic minimum miscible pressure (MMP). Initial history calibrations of primary, secondary and tertiary recovery were conducted as the basis for the study. After a good match was achieved, an optimization approach consisting of a proxy or surrogate model was constructed with a polynomial response surface method (PRSM). The PRSM utilized an objective function that maximized both oil recovery and CO2storage. Experimental design was used to link uncertain parameters to the objective function. Control variables considered in this study included: water alternating gas cycle and ratio, production rates and bottom‐hole pressure of injectors and producers. Other key parameters considered in the modeling process were CO2purchase, gas recycle and addition of infill wells and/or patterns. The PRSM proxy model was ‘trained’ or calibrated with a series of training simulations. This involved an iterative process until the surrogate model reached a specific validation criterion. A sensitivity analysis was first conducted to ascertain which of these control variables to retain in the surrogate model. A genetic algorithm with a mixed‐integer capability optimization approach was employed to determine the optimum developmental strategy to maximize both oil recovery and CO2storage. The proxy model reduced the computational cost significantly. The validation criteria of the reduced order model ensured accuracy in the dynamic modeling results. The prediction outcome suggested robustness and reliability of the genetic algorithm for optimizing both oil recovery and CO2storage. The reservoir modeling approach used in this study illustrates an improved approach to optimizing oil production and CO2storage within partially depleted oil reservoirs such as FWU. This study may serve as a benchmark for potential CO2–EOR projects in the Anadarko basin and/or geologically similar basins throughout the world. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd.

Improving geological and process model integration through TIN to 3D grid conversion

The ability to extract properties from 3D geological framework models for use in the construction of conceptual and mathematical models is seen as increasingly important, however, tools and techniques are needed to support such information flows. Developing such methodologies will maximize the opportunity for information use and re-use, this is particularly important as the true value of such assets is not always known when they are first acquired. This paper briefly describes the cultural and technical challenges associated with the application of information derived from 3D geological framework models by hydrogeological process models. We examine how these issues are being addressed and present a tool, SurfGrid, which allows a user to generate 3D grids (voxels) of parameterized data from a series of geological surfaces.The procedures and tools described offer the ability to re-use expensively created assets by providing user friendly techniques that enable multidisciplinary scientists to extrapolate property distributions from geological models.

Improved understanding of groundwater flow in complex superficial deposits using three-dimensional geological-framework and groundwater models: an example from Glasgow, Scotland (UK)

Groundwater models are useful in improving knowledge of groundwater flow processes, both for testing existing hypotheses of how specific systems behave and predicting the response to various environmental stresses. The recent advent of highly detailed three-dimensional (3D) geological-framework models provides the most accurate representation of the subsurface. This type of modelling has been used to develop conceptual understanding of groundwater in the complex Quaternary deposits of Glasgow, Scotland (UK). Delineating the 3D geometry of the lithostratigraphical units has allowed the most detailed conceptualisation of the likely groundwater flow regime yet attempted for these superficial deposits. Recharge and groundwater flow models have been developed in order to test this conceptual understanding. Results indicate that the direction of groundwater flow is predominantly convergent through the permeable, relatively thick Quaternary deposits of the Clyde valley towards the River Clyde, which runs through Glasgow, with some indication of down-valley flow. A separate nearby system with thick and potentially permeable Quaternary deposits, the Proto-Kelvin Valley, may also be a significant conveyor of groundwater towards the River Clyde, although the absence of local data makes any conclusions conjectural. To improve the robustness of the current model there is a need for an overall increase in good quality groundwater-level data, particularly outside central Glasgow. A prototype groundwater-monitoring network for part of Glasgow is an encouraging development in this regard. This would allow the development of a time-variant groundwater model which could be used to study future modelling scenarios.

3-D interpretative modelling applied to the geology of the Kawerau geothermal system, Taupo Volcanic Zone, New Zealand

Successful development of a geothermal system requires reliable information on its permeability and fluid pathways, which can be fault-controlled and/or influenced by the lateral extent of its reservoir rocks. Utilisation of implicit 3-D visualisation and modelling software allows complex geological and structural framework models to be established that support exploration, and help constrain borehole-targeting with reduced drilling risk and cost. The ability to model geology in a 3-D interface has provided new insights regarding the geological framework, controls on deep-seated permeability, volcanic and basement stratigraphic correlations, and geothermal system evolution in a case study from Kawerau, New Zealand.

Integrating data sources for 3D modeling: the Italian activity in the GeoMol Project

The GeoMol Project focuses on the realization of 3D geological models of the Alpine Foreland Basins to support the assessment of subsurface potentials (geothermal energy, underground storage, groundwater, etc.).GeoMol will provide consistent 3-dimensional subsurface information based on a transnational workflow for 3D models production, coherent evaluation methods, and commonly developed criteria and guidelines.These data will be used to implement a 3D geological framework model and conceptual workflows for geo-potential assessment.The main challenge is to integrate data that come in a different domain of the vertical axis, specifically depth for well logs, time for seismic lines, isobaths and isopachs maps in both the domains.The approach proposed by the GeoMol Project will highlight the possible problems in the exploitation of the geopotential related to concurrent use of subsurface and to the presence of potential active faults.

GB3D – a framework for the bedrock geology of Great Britain

In 2011, the British Geological Survey (BGS) decided to begin the assembly of a National Geological Model (NGM) from its existing and on‐going geological framework models comprising integrated national crustal, bedrock, and Quaternary models. The bedrock component is the most advanced of these themes and comprises both the calculated models and a complementary network of cross sections that provide a fence diagram for the bedrock geology of Great Britain. This fence diagram, the GB3D_v2012 dataset, is the subject of this article and is available in a variety of formats from the BGS website (www.bgs.ac.uk) as free downloads. It complements the existing 1:625 000 scale map sheets published by BGS utilizing the same colour schema and geological classification. The 121 component cross sections extend to depths between 1.5 and 6 km; they have an aggregate length of over 20 000 km, and they are snapped together at their intersections to ensure total consistency. The sections are guided by the existing BGS geological framework models where they cut through them; they also take account of the vast wealth of published data on the subsurface structure of Britain both from BGS and in the literature. Much of this is in the form of cross sections, contour maps of surfaces, and thicknesses (isopachs). The fence diagram has been built in the Geological Surveying and Investigation in 3D (GSI3D) software. Utilizing the cross sections and the coverages of the geological units simple 3D volumes can be calculated for the less deformed sedimentary strata. It is envisaged that this dataset will form a useful educational resource for geoscience students and the general public, and also provide the bedrock geology context and structure for regional and catchment scale studies.

A statistical assessment of the uncertainty in a 3-D geological framework model

Three-dimensional framework models are the state of the art to present geologists’ understanding of a region in a form that can be used to support planning and decision making. However, there is little information on the uncertainty of such framework models. This paper reports an experiment in which five geologists each produced a framework model of a single region in the east of England. Each modeller was provided with a unique set of borehole observations from which to make their model. Each set was made by withholding five unique validation boreholes from the set of all available boreholes. The models could then be compared with the validation observations. There was no significant between-modeller source of variation in framework model error. There was no evidence of systematic bias in the modelled depth for any unit, and a statistically significant but small tendency for the mean error to increase with depth below the surface. The confidence interval for the predicted height of a surface at a point ranged from ±5.6 m to ±6.4 m. There was some evidence that the variance of the model error increased with depth, but no evidence that it differed between modellers or varied with the number of close-neighbouring boreholes or distance to the outcrop. These results are specific to the area that has been modelled, with relatively simple geology, and reflect the relatively dense set of boreholes available for modelling. The method should be applied under a range of conditions to derive more general conclusions.

The key to commercial-scale geological CO2 sequestration: Displaced fluid management

The Wyoming State Geological Survey has completed a thorough inventory and prioritization of all Wyoming stratigraphic units and geologic sites capable of sequestering commercial quantities of CO2 (5–15 Mt CO2/year). This multi-year study identified the Paleozoic Tensleep/Weber Sandstone and Madison Limestone (and stratigraphic equivalent units) as the leading clastic and carbonate reservoir candidates for commercial-scale geological CO2 sequestration in Wyoming. This conclusion was based on unit thickness, overlying low permeability lithofacies, reservoir storage and continuity properties, regional distribution patterns, formation fluid chemistry characteristics, and preliminary fluid-flow modeling. This study also identified the Rock Springs Uplift in southwestern Wyoming as the most promising geological CO2 sequestration site in Wyoming and probably in any Rocky Mountain basin. The results of the WSGS CO2 geological sequestration inventory led the agency and colleagues at the UW School of Energy Resources Carbon Management Institute (CMI) to collect available geologic, petrophysical, geochemical, and geophysical data on the Rock Springs Uplift, and to build a regional 3-D geologic framework model of the Uplift. From the results of these tasks and using the FutureGen protocol, the WSGS showed that on the Rock Springs Uplift, the Weber Sandstone has sufficient pore space to sequester 18 billion tons (Gt) of CO2, and the Madison Limestone has sufficient pore space to sequester 8 Gt of CO2.

The use of 3D geological models in the development of the conceptual groundwater model

The conceptual groundwater model is heavily dependent on the geological framework which is used to defi ne the aquifer being studied. In the past, two-dimensional datasets such as geological maps and cross-sections were used in coordination with site-specifi c point data to build a conceptual understanding at the site or catchment scale. This is then simplified and it is this simplifi ed version which is used to build the framework for the numerical groundwater fl ow model. Due to the way the geological framework model and the conceptual groundwater model were generated they could not be viewed together; this inevitably led to a signifi cant loss of information and understanding. With the current rapid developments in 3D modelling software and the increasing availability of digital geological data it is now possible to produce detailed 3D geological models of complex aquifer sequences. In this paper we will use two case studies (Chalk aquifer of the London Basin and the Jurassic limestone aquifer of the Cotswolds) to demonstrate that by developing a detailed 3D geological model signifi cant benefi ts are gained in the understanding and development of the conceptual groundwater model.

3D geological models and their hydrogeological applications: supporting urban development a case study in Glasgow-Clyde, UK

Urban planners and developers in some parts of the United Kingdom can now access geodata in an easy-to-retrieve and understandable format. 3D attributed geological framework models and associated GIS outputs, developed by the British Geological Survey (BGS), provide a predictive tool for planning site investigations for some of the UK's largest regeneration projects in the Thames and Clyde River catchments. Using the 3D models, planners can get a 3D preview of properties of the subsurface using virtual cross-section and borehole tools in visualisation software, allowing critical decisions to be made before any expensive site investigation takes place, and potentially saving time and money. 3D models can integrate artificial and superficial deposits and bedrock geology, and can be used for recognition of major resources (such as water, thermal and sand and gravel), for example in buried valleys, groundwater modelling and assessing impacts of underground mining. A preliminary groundwater recharge and flow model for a pilot area in Glasgow has been developed using the 3D geological models as a framework. This paper focuses on the River Clyde and the Glasgow conurbation, and the BGS's Clyde Urban Super-Project (CUSP) in particular, which supports major regeneration projects in and around the City of Glasgow in the West of Scotland.

Combining geologic data and numerical modeling to improve estimates of the CO2 sequestration potential of the Rock Springs Uplift, Wyoming

Abstract We present results from the first stages of a detailed three dimensional analysis of the geologic CO 2 sequestration potential of the Rock Springs Uplift (RSU), located in south-western Wyoming. This site is of particular interest because of the collocated 2.1 GW Jim Bridger coal burning power plant and the possibility of additional power plants being developed in the area to take advantage of the abundant coal reserves in the RSU region (i.e. the Southern California Edison CEPL project). The Rock Springs Uplift is a huge asymmetric dome structure with two superior target sequestration reservoirs located beneath a 1500 m thick sequence of Cretaceous shale. The target reservoirs, the Weber Sandstone and Madison Limestone, with thicknesses of greater than 200m and 75m respectively, are located at depths where pressures are well above the critical point of CO 2 . Seismic data reveal that the structure of the RSU creates an ideal trap for buoyant supercritical CO 2 . The target reservoirs currently contain high salinity sour brines (35,000-80,000 ppm) with little or no economic value. Reservoir continuity inferred from well logs and cores and high average measured porosity (10%) and permeability (10-75 md) led to initial screening estimates on the order of 26 billion tons of CO 2 for the storage capacity of the structure. This paper focuses on calculations that will help to refine the initial capacity estimates through the use of high resolution multiphase numerical models. First we present an analysis using a system level simulator, CO2-PENS, to differentiate between two injection depths in the Weber on the basis of the costs associated with on-site drilling and pipelines for a range of permeabilities. The deeper site is analogous to the subsurface near the Jim Bridger Power Plant (JBPP), while the shallower site is analogous to the crest of the RSU. Results of this analysis show that deeper injection may be more cost effective. Next, we develop a 3-D computational hydrostratigraphic model and simulate injection of CO 2 near the Jim Bridger Power Plant. Utilizing existing seismic and wellbore data, a geologic framework model has been created in EarthVision (i.e., 3D model building and visualization software). From this model, hydrostratigraphic units were extracted and a 3-D computational mesh for a 16×16 km section of the RSU structure was constructed. This model is used to simulate injection of 80% of the total CO 2 emissions from the 2.1 GW JBPP (483 kg/s or 15 Mt/year) into the Weber formation for two cases. The first case assumes a very high permeability in the Weber and needs only one injection well, while the second case assumes a lower permeability and uses 9 injection wells. The major differences between these two examples are the amount of CO 2 that dissolves into the formation brines and the areal extent of the resulting plumes. Because the low permeability case requires more injectors, the injected CO 2 is exposed to a larger volume of reservoir rock and leads to a higher percentage of the total injected CO 2 being dissolved in the formation water. The focused injection for the high permeability case leads to more CO 2 remaining in the supercritical state and longer up-dip transport. Finally, both cases show that both diffusive and advective transport into the surrounding strata may significantly increase the storage potential of the RSU.

3D geologic framework models for regional hydrogeology and land-use management: a case study from a Quaternary basin of southwestern Quebec, Canada

During a regional hydrogeologic survey in the St. Lawrence Lowlands, Canada, a computer-based 3D Geologic Framework Model (GFM) was constructed to obtain a consistent representation of this typical Quaternary glaciated basin over a 1,400 km2 area. Such a detailed stratigraphic reconstruction was needed because the Quaternary sediments control the recharge to the underlying regional fractured rock aquifer and also because buried granular aquifers are partly connected to the regional system. The objectives of this geomodeling effort are 1) to improve understanding of subsurface conditions above the regional aquifer and; 2) to provide a common stratigraphic framework for hydrogeologic applications. The method draws on knowledge-driven discrete modeling using gOcad, as well as standardization and quality control procedures to maximize the use of a multisource database. The resulting model represents the bedrock topography and the complex stratigraphic architecture of overlying sediments. The regional till aquitard, the marine clay aquiclude and the buried granular aquifers have been modeled with unprecedented details thus providing a well-constrained 3D hydrostratigraphic framework. The recharge zones of the rock aquifer represent about 35% of the study area. Buried granular aquifers are directly connected to the regional aquifer system over about 10% of the area. The model allows several applications such as assessing aquifer vulnerability and areal groundwater recharge rates; improving the GFM inter-operability with groundwater modeling systems would be the next logical step.