Shemin Ge - US grants

9418561 Ge Fluid flow, rock deformation , heat transfer, and ;mass transport are coupled processes in deforming geologic systems. The coupled effects among these factors have been recognized for their importance in thrust faulting, ore formation, metamorphism, and lubrication of faults during earthquakes. One or more of the coupling processes are often simplified or overlooked. A fully coupled numerical model will be developed and applied to study and physical interaction processes in two geologic settings: sedimentary basins and accretionary prisms. As new features, heat and mass transport are coupled with tectonic deformation, hydraulic permeability is considered a functions of stress and time, and tectonic loading is simulated as a gradual process rather than an instantaneous event. There are two main objectives of this study. The first is to construct a generic model to solve the coupled equations of deformation , fluid flow, heat transfer, and mass transport in geologic medial. The second is to apply the model to study two geologic systems: a sedimentary foreland basin, the Arkoma Basin in Arkansas, and an accretionary prism, the Barbados Accretionary Complex. This research will improve current understanding of the processes involving heat and mass transport in fluids during the history of the tectonic evolution. The application to the sedimentary basin provides a quantitative connection between tectonic events, fluid migration, and ore deposition. The application to the accretionary prism will contribute to the on- going efforts to explain the thermal and chemical anomalies observed in the Ocean Drilling Programs. The work combines analytical scaling, numerical modeling, and case studies. Scaling analysis of the governing equations identifies the relative importance of different coupling mechanisms under simplified conditions. The numerical modeling provides detail solution to the coupled processes under more complicated and realistic geologic conditions. The generic simulations will be designed to test sensitivities of hydrologic, mechanical, and thermal parameters.

9804789
Ge

Natural rock fractures exist at all scales in the earth's upper crust. They play a major role in groundwater movement, solute transport, and waste isolation in geologic media. Characterizing fluid flow and mass transport in fractured rocks depends on our knowledge of how fluid transports through individual fractures. Yet fluid flow in fractures bounded by two rough surfaces is complex. Important questions on the validity of the cubic law and the Reynolds equation for rough fractures have been studied by many. The general conclusions are that the cubic law can only provide a qualitative description of flow rate, the Reynolds equation is not valid for rough fractures and effects of aperture and tortuosity need to be included in better governing flow laws. The primary goals of this research are (1) to systematically explore and quantify the effects of fracture roughness, tortuosity, and the formation of flow channeling on governing flow laws, and (2) to develop a better governing flow law for rough fractures by understanding the fluid transport mechanisms. Specifically, I will attempt to achieve the following objectives: (1) develop a rational method to characterize fracture geometry of natural rocks, (2) investigate the formation of channelized flow paths in generated and profiled fractures, (3) examine the conditions under which the modified Reynolds equation is valid, (4) identify the transitional flow regime from Darcian to non-Darcian flow, and (5) construct a better governing law that captures the dominant features of fluid transport in rough fractures. I will employ an array of theoretical approaches and utilize the existing lab experimental data to achieve these objectives. The Reynolds equation, the modified Reynolds equation including geometric variables of local aperture and tortuosity, and the Navier-Stokes equations will be solved numerically to simulate fluid flow in rough fractures. The Lattice Boltzmann method will be used for simulating both linear and non-linear fluid transport in fractures with complex geometries. The proposed research represents a comprehensive theoretical attempt to examine the governing laws for fluid transport in rough rock fractures.

The PIs will develop a 3-D model of the fluid and thermal flow along strike in the Barbados Accretionary Complex considering both thermal and geochemical transport. The modeling effort will be directed at understanding of the interrelationships between tectonic and gravitational stress, fluid flow and thermal and geochemical transport in actively deforming sediments. The application of 3-D modeling in this and other complexes will assist in the planning of future drilling and seafloor observtory projects and in development of global fluid, heat and geochemical budgets.

This project will study the hydrodynamic response of subduction zones to seismic events by using an analytical model of coseismic pore pressure generation and a numerical model of fluid flow following an earthquake. The results will help make better use of pore pressures as strain indicators. As observatories that monitor pore pressure are established in subduction zones, it will be necessary to understand how pressure changes will vary with deformation style and magnitude, how flow systems will respond to seismic events, and how thermal or geochemical anomalies may be generated by coseismic deformation. The results will also help determine what drilling and monitoring strategies will yield the greatest information concerning deformation and fluid flow in subduction complexes.

0610027
GE
Current understanding of fault-zone permeability at regional scales is limited. Particularly,permeability measurements across faults are scarce. Yet, there are clear indications that faults
have large hydrogeologic impacts on various geologic processes at this scale, as evidenced by
variable hydraulic head gradients, geochemical and geothermal anomalies across faults. There
remain questions that are scientifically fundamental and practically significant regarding largescale
permeability of fault zones and their impact on aquifers. For example, how geologic and
hydrologic information can be best integrated to effectively constrain regional-scale fault
permeability? While existing knowledge on fault permeability at small scales is indispensable
scientifically, ultimately, it is the regional-scale permeability that is needed in conceptual and
numerical models for solving problems related to water resource management and transport of
fluid, solute, and energy in the Earth's crust.
The scientific objective of this research is to characterize fault-zone permeability at the wellfield
to regional scale with constraints from field-based structural observations, hydrogeologic
testing, and interpretation from conceptual and numerical modeling. The basis hypotheses are
that distinctive hydrogeologic responses around a fault could be observed from cross-fault
aquifer tests and that fault-zone permeability features could be established from a comprehensive
understanding of the outcrop structural characteristics, borehole data of host rocks, and
hydrogeologic tests conducted at multiple scales. Using the Elkhorn thrust fault in Colorado as a
field site, the research plan consists of the following: (1) to characterize the geology and internal
structure of the fault zone to better understand the influence of juxtaposition of different
lithologies on fault-zone hydrogeologic properties, (2) to drill and core new boreholes through
the fault zone to obtain direct field observations for fault-zone permeability, (3) to conduct crossfault
pumping tests in the new and preexisting holes to provide the much need direct
measurements on fault-zone permeability, and (4) to develop a fault-zone permeability model,
through numerical modeling that integrates geologic, hydrogeologic, and geophysical field data.
Three aspects of the intellectual merit are recognized. First, the study takes a new direction
in characterizing fault-zone permeability by closely linking geologic observations and
hydrogeologic testing data. Second, this proposed research offers the opportunity to gain
hydrogeologic insight into a particular type of fault that is common but highly understudied - a thrust fault with a crystalline hanging wall and sedimentary footwall at regional basin scales. Finally, the cross-fault permeability tests coupled with geologic characterization planned in this research will be a significant advance in characterizing fault-related permeability by providing much-needed field measurement data.
The major aspect of the broader impact of this proposed research is on enhancing
undergraduate students experience in hydrogeology, in addition to training graduate students and contributing to better groundwater resource management in the western US. This research will benefit a large group of undergraduate students. Undergraduate students will be involved in all stages of this project. Specific approaches to implement this commitment include: (1) Recruit top undergraduates to conduct honor theses, (2) Field exercise related to an upper-division hydrogeology class. Groundwater level mapping and aquifer tests can be incorporated into class related activities, and (3) Drilling new boreholes will be coordinated so that students can observe
the operation. Finally, the PIs plan to co-teach a two-credit two-week summer undergraduate field hydrogeology class. The research will provide an excellent venue for many different projects for this field class and help to realization of this plan.

Understanding the interplay between out-of-sequence thrusts, fluid expulsion, underplating, and the behavior of the plate boundary fault is of fundamental importance to the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE), but these processes have not previously been examined through fluid flow and deformation modeling. Accordingly, this modeling study will address the impact of these major processes on pore pressures and fluid flow within the prism, mega-splay fault, and plate boundary fault. The modeling will be implemented using an existing software package ABAQUS. This package offers the ability to simulate the major features important to this modeling, will allow modeling results to be reproducible by other researchers, and is flexible enough to accommodate needs of future subduction zone modeling.
The model will be applied to the Kii transect of the Nankai subduction zone and used to test the following interrelated hypotheses:
Hypothesis 1: The mega-splay fault system significantly alters the patterns of excess pore pressures and porosity loss within the accretionary complex.
Hypothesis 2: The hydrologic role of the Nankai mega-splay system can be illuminated through observation of pore pressures, porosities, and fluid chemistry.
Hypothesis 3: Underplating rejuvenates fluid expulsion at the base of the accretionary prism by transferring sediments to a different stress state and by moving the decollement zone to a less dewatered area.
Although this application of the modeling is to the Kii transect of the Nankai subduction complex, an assessment of the importance of underplating and out-of-sequence thrusting for subduction zone dewatering and deformation will be useful for other subduction zones, as well as for workers in fold and thrust belts. Splay faulting and underplating are commonly inferred features that could greatly alter pore pressure and porosity distributions (and thus seismogenesis) in many subduction zones.

Broader Impact
Understanding seismogenic zone processes has great societal impact related to earthquake and tsunami hazards. This study will constitute an initial step in the long-term investigation of the seismogenic zone. Modeling conducted early in the investigative process can help to shape scientific strategies during drilling and monitoring. The use of the ABAQUS software package will expand the ability of the subduction zone modeling community. Model input data sets will be made available to other researchers. As an active proponent in NanTroSEIZE, Liz Screaton will directly communicate modeling results to fellow proponents and at future workshops and NanTroSEIZE-related meetings. In addition, general interest conclusions will be published in scientific journals and presented at national scientific meetings. This project will result in the training of graduate students. At University of Florida, it will be adapted to either one PhD or two M.S. students. At University of Colorado, the project work will involve a student (either MS or PhD) in the modeling. The graduate students will present at scientific meetings and the project will be a significant component of their dissertation or thesis.

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).

CMG Research: Multiscale Nonlinear Domain Decomposition Method for Modeling the Impact of Climate Change on Groundwater Resources

S. Ge, Department of Geological Sciences, University of Colorado
X. Cai, Department of Computer Science, University of Colorado
C. Li, Department of Applied Mathematics, University of Colorado
M. Williams, Department of Geography, University of Colorado

Continuing climate change poses uncertainties on future water resources. The water cycle encompasses fundamental processes that link various elements of climate and water resources. Holding approximately 30% of Earth's fresh water, groundwater?s enormous storing capacity can be an effective buffer in regulating more drastic hydrologic events on the surface, therefore, plays an important but often overlooked role in long-term sustainability of water resources. High altitude mountainous regions are vital source areas for water. Hydrologic processes in high-altitude regions are particularly sensitive to climate change because of the presence of snow, glaciers, and permafrost. Yet, basic questions remain regarding how groundwater is replenished at its source by mountain recharge, the size of groundwater reservoirs, as well as how permafrost influences groundwater. Modeling the groundwater flow processes involving mountain recharge and permafrost faces mathematical challenges due to nonlinearity of the governing equations and multiscale nature of the spatial and temporal domains.

The objective of the research is to develop a more accurate mathematical model and a new robust computational algorithm and high performance software to study the impact of climate change on groundwater resources in mountain watersheds, with a focus on quantifying mountain recharge and permafrost hydrology. The research plan is to first develop a mathematical model that will be capable of handling coupled fluid flow and heat transport in complex geologic systems in multiscale spatial and temporal domains. Second, field hydrogeologic study at two sites will be conducted to gather data for testing the mathematical model. The final stage is to conduct numerical simulations to assess the response of groundwater storage and flow in mountain watersheds to future climate change scenarios.

First, this study will contribute to our scientific knowledge on water cycle processes at multi spatial and temporal scales. In particular, this study will make a unique contribution to strengthening the subsurface element of the water cycle, increasing knowledge on mountain recharge, and integrating little known permafrost hydrology into a water resource study. Second, highly parallel and robust numerical algorithms and software will be developed for the coupled multi-physics system describing the water cycle processes. Third, the proposed mathematical model development will be a substantial contribution to hydrogeologic sciences. Dealing with multiscale fluid flow problems in heterogeneous geologic media has been a long standing challenging. Development of a robust computational algorithm allows efficiently modeling of hydrogeologic systems at such a comprehensive and integrated level that would be difficult to achieve by either mathematicians or geoscientists alone.

Water resource sustainability and climate change are pressing issues of global and local concern. This study will benefit long term planning of water resources and increase general public?s knowledge on the linkage between climate and water resources, by dissimilating results through local media and public lectures. The new computational algorithm implemented by a robust and versatile software will be transferable to other areas of application and available to other researchers. The cross-discipline nature of this project will afford students in mathematics and geosciences a unique opportunity to interact with each other in intellectual and physical settings that differ from those they are used to. This will be achieved by requiring students to take classes outside their home departments, math students to participate in field work, geoscience students to be trained in computational mathematics. Finally a joint math-geosciences seminar will be established to involve all project personnel. By encouraging broad participation, this seminar will foster more and sustained future collaborations between mathematics and geosciences.

This project is aimed at quantifying how fluid flow in evaporite (salt) deposits controls 3D brittle strain in the upper crust, in addition to solute transfer and it's connections between Earth's surface and subsurface. The research will help understand how transient fluid flux drives short-term brittle strain at timescales of days to decades and distances of tens of meters to kilometers. The research team will characterize active surface deformation with 1:5,000 scale field mapping and construction of cross sections, analysis of InSAR scenes, and installation of a three-component extensometer (creep meter) across a rapidly slipping boundary fault. In addition researchers will assess patterns and rates of surface and groundwater flowing through or directly into buried salt and its effect on rock strength as governs by hydraulic weakening and dissolution. Three-dimensional mechanical modeling will be undertaken to test models constrained by observed strain at the surface, fluid flux, groundwater modeling, structural geology and topography. The goal is to fully characterize how fresh water moves through the salt system, how that modulates plastic strain by dissolution and changes on the strength of halite and the role topography plays in coupled surface and subsurface processes. The work?s broader significance includes understanding how fluid flow and strain in salt systems evolves at scales not available by other means. The researchers are particularly interested in determining how transient surges in plastic salt flow might respond to input of the seasonal influx of surface runoff and groundwater recharge. The field work is located in the Paradox evaporite basin in eastern Utah, a region noted for its extraordinarily well-exposed rocks and wealth of available surface and subsurface data.

This work will build on the recent discovery of transient surges in unconfined salt bodies in western Iran and the Dead Sea in Israel. These structures, which consist of emergent domes and flows of pure rock salt are modern examples of geologic structures analogous to glaciers and are similar to features in areas such as the Gulf of Mexico that contain great petroleum reserves. The research will define the conditions that control deformation and growth of salt structures and relate this to conditions such as the inflow of fresh water and outflow of saline brines within them. These studies will utilize a wide array of techniques and data previously unavailable in past studies. The ultimate goal is thus to define the physical conditions that control and guide their development in order that this may be applied in general to other salt structures around the world. On a global scale, this work is of interest to responsible resource exploration in salt basins for hydrocarbons. For instance the Deepwater Horizon well that created the oil spill in the Gulf of Mexico in 2010 was being drilled into a salt structure, and the cause of the blowout was an unforeseen increase in fluid pressure. In addition, this work holds the promise to quantify the saline brine influx into the Colorado River and shallow groundwater and its effect on the degradation of water quality in the largest source of fresh water in the southwestern United States.

1649919
Limerick, Patricia N.

After a very brisk boom over the past decade, oversupply of petroleum has led to a steep drop in prices. This "bust" has interrupted the rapid expansion of well drilling in conjunction with hydraulic fracturing, and a trend of shutting down and capping, closing, and even abandoning wells has accelerated. A wide range of stakeholders are often improvising procedures to manage this new phase constrained by declining financial resources. The premise of this workshop is that the history of the American West holds, in a multiplicity of abandoned mines, a century and a half's worth of directly relevant case studies. A workshop for coming to grips with the history and material impact of Western mining, and applying that understanding to the current circumstances of Western oil and gas production, presents an opportunity to bring scientists, engineers, historians, and policy scholars into an innovative, dynamic, and consequential conversation.

The workshop will place knowledge of subsurface activities in their broader context as practices embedded in intended and unintended historical legacies and provide a novel framework for anticipating and mitigating environmental, economic, and social impacts of contemporary oil and gas development. The central premise is that a historic-scientific approach will produce a life-cycle perspective on resource extraction and suggest practices to minimize the negative long-term consequences of intensive oil and gas production. An integrated review of past, current, and emerging sensing technology will identify data gaps and promote better monitoring and management of risk from subsurface resource extraction. Workshop participants will be selected to bridge scientific and lay/local knowledge of the impact of human activities in the subsurface. The costs and benefits of subsurface enterprises will be identified, along with their distribution at scales of neighborhood, town, city, suburb, county, state, reservation, region, nation, and planet. The workshop will draw on the expertise of the Center of the American West, in casting scholars in the humanities and social sciences as participants alongside scientists and engineers in managing the impacts of energy, water, and mining activities, rather than bringing them in as translators after the scientists have done their work. The workshop will foster public discussion of management of the subsurface by bringing together heretofore disparate voices of scientists, engineers, humanists, and local residents representing diverse communities. A published document, possibly a journal special issue, will present subsurface management strategies generated in the workshop based on review of scientific findings about the impacts of oil and gas development placed in a context of political, economic, social, and cultural relations, identified through using knowledge of historic mining. Workshop outcomes also will provide a framework for regulators and stakeholders interested in producing new policy and regulations, and create opportunities for partnerships between industry and academic researchers. Ideas for interdisciplinary approaches for teaching classes about the subsurface will be developed, including recruitment and training of researchers and other experts as guest speakers, curriculum guides, and class materials representing science, technology, and the humanities. New educational developments begun at the University of Colorado Boulder will provide a grounded example that can be made available to other universities and colleges.

The episodes of torrential rainfall in September 2013 in the Colorado Front Range caused widespread flooding in the area. While floodwater receded within days, data from subsurface suggested substantial changes in groundwater storage long after the flood. This study seeks to understand the changes in groundwater storage in response to extreme rainfall events. Understanding the effects of extreme rainfall events can provide the basis for predicting aggregated effects over longer temporal and larger spatial scales. By assessing the potential for shallow soils and deeper aquifers to serve as natural storages for floodwaters, this study could provide a scientific basis for water managers to assess the excess water stored during extreme rainfall events and timely utilize the resource when it is released back to streams. The project will have a substantial educational element. Graduate students will be directly involved in research. A two-week undergraduate field course will incorporate some in-situ aquifer tests proposed for this study. A groundwater flow computer model will be created for an undergraduate modeling class project. These field and modeling plans will benefit approximately 90 undergraduate students and offer them the opportunity to learn practical skill sets and a real research experience in water sciences. The project plan also includes recruiting and working with students from underrepresented groups through the RESESS program, an NSF supported summer internship program dedicated to increasing the diversity of students entering geosciences.

The overall goal of this research is to better understand the dynamic response of watershed-scale subsurface hydrologic systems to extreme rainfall events. The specific research questions are: (1) How much could precipitation infiltrate into the vadose zone during extreme rainfalls? (2) How much does the subsurface water storage change in the event of extreme rainfall? (3) To what temporal and spatial extent could extreme rainfalls impact subsurface systems? The research plan consists of three components. The first is to collect and analyze hydrologic data that will provide information for conceptualizing the system and the parameters for model calibration. The second is to conduct in-situ and laboratory measurements to characterize the hydrologic properties of the vadose zone and the saturated zone. The third is to develop an integrated vadose-zone and saturated-zone flow model to synthesize data, test hypotheses, and address research questions. The Upper Boulder Creek west of Boulder, Colorado, will be utilized as a test bed because of the availability of existing hydrologic data spanning over the pre- and post-extreme precipitation periods. Using a physics-based mass-balance approach, this study offers a quantitative modeling framework that links precipitation, subsurface flow, and stream baseflow at watershed scales, with an emphasis on rigorous modeling of infiltration processes in the vadose zone. This study will shed new light on infiltration into the vadose zone, dynamic changes in subsurface water storage, and the temporal and spatial extent that a watershed subsurface system could be affected under extreme rainfall events. The study site includes varying geology and geography, making the results transferrable to other regions. This study will advance modeling integrated vadose zone and saturated zone flow through utilizing latest modeling capability and taking advantage of data availability. On the basis of its contribution to rigorous modeling infiltration and site transferability, this study is potentially transformative.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.