Philip H Stauffer

Los Alamos National Laboratory | LANL · Earth and Environmental Sciences Division

We present a revised form of the energy balance for the coupled thermodynamics of liquid water flowing in porous media and give examples of situations where a commonly used formulation based on transport of enthalpy leads to erroneous results. Assuming negligible contribution from kinetic energy as well as sources and sinks such as energy from radi...

Barometric pumping caused by atmospheric pressure fluctuations contributes to the motion of gases in the vadose zone. While the resulting gas transport is often negligible in unfractured porous rocks, rates of transport in fractured media can be significant. Deep atmospheric pumping has implications for nuclear gas detection, water balance, and con...

There is a growing need for disposal of high‐level nuclear waste. To reduce uncertainty associated with brine availability to repository excavations in salt formations, a collaboration between Sandia, Los Alamos, and Lawrence Berkeley National Laboratories is performing a series of borehole‐scale coupled process tests. Here, we report on the first...

Plain Language Summary The existence of methane on Mars is a topic of significant interest because of its potential association with subsurface microbial life. Measurements of methane in the atmosphere of Mars indicate that its abundance fluctuates over time. Although the source of methane is unknown, it most likely comes from below the surface of...

A scientific collaboration between the U.S. and Israel is underway to assess the suitability of a potential site for subsurface radioactive waste disposal in the Negev Desert, Israel. The Negev Desert has several favorable attributes for geologic disposal, including an arid climate, a deep vadose zone, interlayered low-permeability lithologies, and...

This paper contains a comparison of five modelling approaches for a simplified nuclear waste repository in a domal salt formation. It is the result of a four-year collaboration between five international teams on Task F of the DECOVALEX-2023 project on performance assessment modelling. The primary objectives of Task F are to build confidence in the...

Large‐scale discrete fracture network (DFN) simulators are standard fare for studies involving the sub‐surface transport of particles since direct observation of real world underground fracture networks is generally infeasible. While these simulators have successfully been used in several engineering applications, estimates of output quantities of...

Detection of underground nuclear explosions (UNEs) require a sophisticated understanding of gas transport through fractured geological media. This is because surface detection of some signature gaseous radionuclides, such as xenon, is a strong indicator of a subsurface nuclear event. The complicated physics involved in gas transport in explosively...

The coupling and interactions among rock deformation, fluid flow, heat transfer and geochemical reactions has become an essential topic in complex subsurface systems for geothermal energy production. To improve the understanding and minimize the uncertainty in subsurface geothermal energy production operations, a new coupled Thermo-Hydro-Mechanical...

Surface detection of noble gas radionuclides (RN) is critical to identify underground nuclear explosions (UNEs). However, predicting RN gas migration in the subsurface following a UNE involves complex processes of gas migration through the rock matrix and fracture network, rock damage, and the opening and closing of natural faults and fractures, wh...

A systematic approach is used to assess the leakage risk of legacy wellbores using available wellbore information from a site in Louisiana, USA. The proposed approach assesses potential risk of groundwater contamination resulting from fluid leakage in legacy wells associated with carbon sequestration operation. The assessment incorporates several k...

We present an analysis and interpretation of potential cliff stability at a low-level waste disposal facility at Los Alamos National Laboratory, New Mexico, using cliff morphologic and fracture characteristics coupled with carbon-14 surface exposure dating. Our study is important as it directly bears on the licensing criteria for low-level radioact...

Exploratory data analysis (EDA) for functional data—data objects where observations are entire functions—is a difficult problem that has seen significant attention in recent literature. This surge in interest is motivated by the ubiquitous nature of functional data, which are prevalent in applications across fields such as meteorology, biology, med...

Simulations of rock damage and gas transport following underground explosions that omit preexisting fracture networks in the subsurface cannot fully characterize the influence of geo-structural variability on gas transport. Previous studies do not consider the impact that fracture network structure and variability have on gas seepage. In this study...

In recent years, the Tunable Laser Spectrometer within the Sample Analysis at Mars (TLS‐SAM) instrument on board the Mars Science Laboratory (MSL) Curiosity rover has detected methane variations in the atmosphere at Gale crater. Methane concentrations appear to fluctuate seasonally as well as sub‐diurnally, which is difficult to reconcile with an a...

Plain Language Summary Fractured rocks are important to study to understand subsurface geology, hydrology, and engineered systems. Individual fractures often form connected networks with other fractures, which complicates the prediction of flow and transport behavior. In this work, we study how changes in fracture network properties such as the var...

The inherent uncertainty of subsurface fracture characteristics requires an ensemble-based approach where multiple network realizations are generated to represent a single physical system. However, the computational cost of these simulations is often prohibitive for carrying out an adequate number of simulations to obtain stable statistics for many...

Successful deployment of geological carbon storage (GCS) requires an extensive use of reservoir simulators for screening, ranking and optimization of storage sites. However, the time scales of GCS are such that no sufficient long-term data is available yet to validate the simulators against. As a consequence, there is currently no solid basis for a...

In recent years, the Sample Analysis at Mars (SAM) instrument on board the Mars Science Laboratory (MSL) Curiosity rover has detected methane variations in the atmosphere at Gale crater. Methane concentrations appear to fluctuate seasonally as well as sub-diurnally, which is difficult to reconcile with an as-yet-unknown transport mechanism deliveri...

Underground nuclear explosions produce noble gases that can migrate to the surface and become detectable by atmospheric monitoring tools. However, it is challenging to predict radionuclide gas migration in the complex engineered and natural subsurface systems due to several issues. These issues include generation of complex fracture networks near a...

The complex coupling interaction phenomena among rock mechanics, fluid flow, heat transfer and geochemical reactions has become a critical topic in complex subsurface systems including the production of unconventional oil and gas. In this paper, we introduce a fully coupled Thermo-Hydro-Mechanical-Chemical (THMC) framework that is being developed a...

Modeling gas flow through fractures of subsurface rock is a particularly challenging problem because of the heterogeneous nature of the material. High-fidelity simulations using discrete fracture network (DFN) models are one methodology for predicting gas particle breakthrough times at the surface, but are computationally demanding. We propose a Ba...

We model flow and transport in three-dimensional fracture networks with varying degrees of fracture-to-fracture aperture/permeability heterogeneity and network density to show how changes in these properties can cause the emergence of anomalous flow and transport behavior. If fracture-to-fracture aperture heterogeneity is increased in sparse networ...

Successful deployment of geological carbon storage (GCS) requires an extensive use of reservoir simulators for screening, ranking and optimization of storage sites. However, the time scales of GCS are such that no sufficient long-term data is available yet to validate the simulators against. As a consequence, there is currently no solid basis for a...

Mesh generation lies at the interface of geological modeling and reservoir simulation. Highly skewed or very small grid cells may be necessary to accurately capture the geometry of geological features, but the resulting poorly scaled or small grid cells can have a substantial negative impact on simulator accuracy and speed. One way to minimize nume...

Noble gas transport through geologic media has important applications in the characterization of underground nuclear explosions (UNEs). Without accurate transport models, it is nearly impossible to distinguish between xenon signatures originating from civilian nuclear facilities and UNEs. Understanding xenon transport time through the earth is a ke...

Vadose zone transport of tritium and nitrate can be important considerations at radioactive waste sites, landfills, or areas with industrial impacts. These contaminants are of particular concern because they typically have a relatively higher mobility in the subsurface compared to other compounds. Here, we describe a semiarid site with tritium and...

A series of batch experiments were performed to assess the uranium sorption capacity of four mineralogically distinct lithologies from the Negev Desert, Israel, to evaluate the suitability of a potential site for subsurface radioactive waste disposal. The rock specimens consisted of an organic-rich phospho-rite, a bituminous marl, a chalk, and a sa...

Numerical models of geothermal systems commonly capture only the top of a reservoir. Deeper areas of the reservoir are simplified to a boundary at the base of the model domain. Commonly, the basal boundary is given either a heat source or a source of mass and enthalpy. We developed and present simple numerical experiments which demonstrate that the...

Carbon dioxide (CO2) storage in deep saline aquifers is a vital option for CO2 mitigation at a large scale. Determining storage capacity is one of the crucial steps toward large-scale deployment of CO2 storage. Results of capacity assessments tend toward a consensus that sufficient resources are available in saline aquifers in many parts of the wor...

Low temperature hydrothermal systems hosted in the volcanic oceanic crust are responsible for ∼20% of Earth's global heat loss. Marine sediment ponds comprise an important type setting on young ridge flanks where hydrothermal circulation advectively extracts lithospheric heat, but the nature of coupled fluid‐heat transport in these settings remains...

Gas samples taken from two historic underground nuclear tests done in 1989 at the Nevada National Security Site (NNSS), formerly the Nevada Test Site (NTS), were examined to determine how xenon isotopes fractionate because of early-time cavity processes, transport through the rock, or dispersal through tunnels. Xenon isotopes are currently being us...

This paper describes a system-level risk assessment for the Shenhua CO2 storage site, China, using the National Risk Assessment Partnership Integrated Assessment Model for Carbon Storage (NRAP-IAM-CS). We begin by determining the optimal number of Monte Carlo (MC) simulations to achieve CO2 and brine leakage result convergence. Then, we calculate m...

Barometric pumping is a gas transport mechanism that has important implications for many applications involving subsurface gas seepage processes. This study provides the first continental-scale analysis of barometric-pumping efficiency potential based on meteorology. We quantified the barometric-pumping efficiency potential at 1,257 locations acros...

Deep CO2 storage reservoirs show a wide range of heterogeneous structures across different scales. Here, we show how high-resolution heterogeneity in both permeability and capillary entry pressure control dissolution and local capillary trapping of supercritical CO2 (ScCO2). Prior works mainly considered homogeneous reservoirs or simplified heterog...

In this study, we investigate formation damage due to acidization and water injection tests into the naturally fractured carbonate Middle Duperow Formation at Kevin Dome, Montana, potentially diminishing the chance of a future successful Geological Carbon Sequestration (GCS) project. Multiple well-test analytical models, correlated with core descri...

In this study, we integrate geologic and engineering data of a naturally fractured carbonate reservoir at the Kevin Dome, Montana. Well test data are correlated with core description, geochemical and lithology study to determine the flow behavior and communication within the injection test interval and to the surrounding area. Based on a dual-conti...

An underground nuclear explosion (UNE) generates radioactive gases that can be transported through fractures to the ground surface over timescales of hours to months. If detected, the presence of particular short-lived radionuclides in the gas can provide strong evidence that a recent UNE has occurred. By drawing comparisons between sixteen similar...

CO2 capture and storage (CCS) technology is likely to be widely deployed in the coming decades in response to major climate and economics drivers: CCS is part of every clean energy pathway that limits global warming to 2°C or less and receives significant CO2 tax credits in the United States. These drivers are likely to stimulate the capture, trans...

Utilizing historical data from the U.S. nuclear test program and freely available barometric pressure data, we performed an analytical barometric‐pumping efficiency analysis to determine factors resulting in late‐time radionuclide gas seeps from underground nuclear explosions. We considered 16 underground nuclear explosions with similar geology and...

CO2 capture and storage (CCS) technology is likely to be widely deployed in coming decades in response to major climate and economics drivers: CCS is part of every clean energy pathway that limits global warming to 2C or less and receives significant CO2 tax credits in the United States. These drivers are likely to stimulate capture, transport, and...

We describe a field study where tracer gas was injected into a subsurface cavity created by a small chemical explosion beneath the water table. The main objective of the study is to compare the migration of sulfur hexafluoride (SF6) and xenon (Xe) through an explosion‐generated fracture network and to study the influence of ground water on gas tran...

Reduced-order models (ROMs) are a widely used and powerful approach to reducing the complexity of pre-dictive physics-based numerical simulations for a wide range of applications, including electronics and fluid mechanics such as geologic CO2 sequestration (GCS). ROMs are critical for optimization, sensitivity analysis, model calibration and uncert...

We develop a computational geometry-based upscaling approach to accurately capture the dynamic processes occurring within and between subsurface fracture networks and the surrounding porous matrix named the Upscaled Discrete Fracture Matrix model (UDFM). Fracture attributes (orientations and apertures) are upscaled and combined with matrix attribut...

The temperature of deep hydrothermal sedimentary reservoirs varies between 50 and 250 ◦ C, while the temperature of injected CO2 can be much below the reservoir temperature. Most past studies did not consider temperature effect on the CO2 dissolution trapping in storage reservoirs. We have performed numerical simulations of coupled multiphase flow,...

We present a set of multiphase flow simulations where supercritical CO\(_2\) (scCO\(_2\)) displaces water at hydrostatic conditions within three-dimensional discrete fracture networks that represent paths for potential leakage through caprock above CO\(_2\) storage reservoirs. The simulations are performed to characterize and compare the relative i...

Saline aquifers, among other potential CO2 storage formations, have been proven to offer the highest storage capacity necessary for commercial-scale carbon capture and storage (CCS) projects. They are an ideal target for emission reduction from coal-fired power plants in the sourcesink model. However, unlike hydrocarbon reservoirs which are typical...

The overarching goal of the research presented is to build a subsurface radionuclide transport model for the vadose zone in the northeastern Negev desert of Israel, in order to assist in evaluating its suitability for radioactive waste subsurface disposal. The Negev desert provides a unique geologic setting because of its arid conditions, deep vado...

We demonstrate that although barometric pressures are complicated signals comprised of numerous frequencies, it is a subset of these frequencies that drive the overwhelming majority of gas transport in fractured rock. Using an inverse numerical analysis, we demonstrate that a single barometric component with seasonally modulated amplitude approxima...