Sheng Dai
Assistant Professor, Geosystems Engineering Georgia Tech College of Engineering
- Atlanta GA
Sheng Dai develops innovative testing techniques to study properties and processes in soils and rocks at elevated pressure and temperatures.
Georgia Tech College of Engineering
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Biography
Dr. Dai earned his BS and MS degrees in civil engineering from Tongji University, China, and MSCE and Ph.D. degrees in civil engineering (geosystems engineering) from Georgia Tech. He worked in the Predictive Geosciences Division at the National Energy Technology Laboratory of U.S. Department of Energy. In 2015, he returned to Georgia Tech and joined the faculty in the School of Civil and Environmental Engineering. He is an affiliated faculty in the Ocean Science and Engineering program and the Strategic Energy Institute at Georgia Tech.
Dr. Dai has strong research and teaching interests in energy geotechnics, geomaterials characterization, geomechanics, and flow in porous media. His group develops innovative testing techniques in combination with advanced numerical modeling to study fundamental properties and BTHMC-coupled processes in soils and rocks at elevated pressure and temperature conditions. His research advances the fields of gas hydrate, enhanced geothermal systems, geological carbon sequestration, subsurface drilling/stimulation, and subsurface sensing and monitoring.
Areas of Expertise
Selected Accomplishments
Class of 1969 Teaching Fellows, Georgia Tech
2016
ORISE Fellowship, NETL/DOE
2013, 2014
Bill Schutz Junior Faculty Teaching Award, CEE/Georgia Tech
2017
George F. Sowers Distinguished Graduate Student Award, Geosystems/Georgia Tech
2013
Education
Georgia Institute of Technology
Ph.D.
Geosystems Engineering
2013
Georgia Institute of Technology
M.Sc.
Geosystems Engineering
2011
Tongji University
M.S.
Geotechnical Engineering
2008
Tongji University
B.S.
Geotechnical Engineering
Affiliations
- Associate editor, Journal of Geophysical Research: Solid Earth
- Task force leader, ISSMGE TC308 - Energy Geotechnics
- Advisory: Pressure Core Advisory Board, USGS, DOI; GOM2 Marine Test Advisory Committee, UT/DOE
- Member: AGU; InterPore; ISSMGE; SEG; ASCE; Geo-Institute
- Reviewer: Geophysical Research Letters; Journal of Geophysical Research; Geochemistry Geophysics Geosystems; Environmental Science and Technology; Advances in Water Resources; etc.
Links
Selected Media Appearances
Geothermal Energy Is a Strong Contender for the Future of Energy
engineering.com online
2018-08-03
As energy consumption grows, it creates a gap between energy produced and energy consumed. Scientists continue to seek new ways to fill this gap with cleaner, renewable sources. Associate Professor Sheng Dai at Georgia Tech’s College of Engineering is focused on one promising energy source from the Earth itself: geothermal energy.
“I suspect that deep geothermal energy is going to make a big impact on the state of clean energy,” Dai said. “Long term, it’s more environmentally friendly and efficient. Plus, it doesn’t rely on other environmental factors. For instance, with solar energy, you’ll have low energy output if it’s overcast or dusty.”
Advances in extracting uranium from seawater announced in special issue
PHYS ORG online
2016-04-21
"Synthesizing a material that's superior at adsorbing uranium from seawater required a multi-disciplinary, multi-institutional team including chemists, computational scientists, chemical engineers, marine scientists and economists," said Sheng Dai, who has technical oversight of the ORNL uranium from seawater program. "Computational studies provided insight into chemical groups that selectively bind uranium. Thermodynamic studies provided insight into the chemistry of uranium and relevant chemical species in seawater. Kinetic studies uncovered factors that control how fast uranium in seawater binds to the adsorbent. Understanding adsorbent properties in the laboratory is key for us to develop more economical adsorbents and prepare them to grab as much uranium as possible."
Selected Articles
Kinetic enhancement of capturing and storing greenhouse gas and volatile organic compound: Micro-mechanism and micro-structure of hydrate growth
Chemical Engineering JournalLunxiang Zhang, Yangmin Kuang, Sheng Dai, Jiaqi Wang, Jiafei Zhao, Yongchen Song
2019
The use of hydrate-based technology for gas capture and storage is highly attractive for environmental mitigation, as it entails low energy penalties and provides gas storage density maximization and long-term storage stability. Although this method has been investigated in extensive researches, its development is restricted by the obscure underlying gas capture micro-mechanisms, elusive micro-structures of stored forms, and insufficient hydrate film growth rates. In this study, the Magnetic Resonance Imaging technique was employed to analyze the hydrate growth micro-processes for greenhouse gas (imitated by CO2, CH4, and various fractions of CO2-CH4 mixed gases) and volatile organic compound (simulated by C2H4 and C2H2 gases) capture and storage. The hydrate film growth was enhanced with the addition of 288 ppm sodium dodecyl sulfate (SDS), which significantly improved the hydrate growth in the cases of hydrocarbon gases, but not CO2 gas due to the competing adsorption of bicarbonate and dodecyl sulfate ions. With SDS, hydrocarbon gas hydrates grew via the patchy model at 65–105 mm/s, and 65–95% liquid water was converted into hydrates for gas capture and storage. However, only about 1.4% water was converted into CO2 hydrates with SDS, at 10.4 mm/s. Thus, a multi-pressure control mechanism for secondary hydrate growth was developed to promote CO2 capture and storage, based on a large amount of dissolved CO2 gas compared to the other investigated gases. The enhanced CO2 capture has important implications for the optimized harmful gas sequestration, due to preferentially patchy hydrate morphologies and associated impacts on permeability.
Particle crushing in hydrate-bearing sands
Geomechanics for Energy and the EnvironmentJongchan Kim, Yida Zhang, Yongkoo Seol, Sheng Dai
2019
The depressurization of natural hydrate deposits to produce methane gas can increase the effective stress in hydrate-bearing sediments, which may induce sand particle crushing. Sand crushing may become detrimental to gas production, because the breakage of sand particles can cause sediment contraction, reduction in permeability, and the generation of finer particles exacerbating solids migration and sand production. This study experimentally investigates particle crushing in tetrahydrofuran hydrate-bearing sands. Sandy specimens with various hydrate saturation are loaded to different stresses (up to 40 MPa) in an instrumented oedometer cell to induce sand crushing. The results show that the presence of hydrate crystals inhibits sand particle crushing. More pronounced sand crushing occurs in specimens with lower hydrate saturation and under higher maximum effective stress. Hydrate crystals can cement neighboring sand particles and constrain the particles from rotating and rearranging during loading. Relatively larger particles in hydrate-bearing sediments experience surface grinding with no significant decreases in particle sizes, and shear-off asperities of the larger particles contribute to an increase in the proportion of smaller particles. The total volumetric strain in hydrate-bearing sediments due to loading can be estimated using the known hydrate saturation and the volumetric strain of hydrate-free sediments subjected to an identical load. The changes in hydraulic conductivity due to sand particle crushing are correlated to the breakage index. The results highlight that gas production from hydrate deposits using depressurization increases the effective stress and the loss of hydrate crystals can exacerbate sand crushing.
Fractal characteristics of unsaturated sands − implications to relative permeability in hydrate-bearing sediments
Journal of Natural Gas Science and EngineeringLele Liu, Sheng Dai, Fulong Ning, Jianchao Cai, Changling Liu, Nengyou Wu
2019
Precise estimation of gas production from hydrate deposits heavily relies on an accurate description of relative permeability to water and gas in hydrate-bearing sediments. Relative permeability innately depicts the competing flow of gas and water phases for the pore spaces in sediments, and thus, is affected by pore characteristics and pore-scale morphology of water and gas. Characterization and quantification of water and gas distribution in pores at various water and hydrate saturation are not always offered. This study aims to establish a fractal theory based relative permeability model considering pore characteristics and the physics of pore-scale water and gas distribution. X-ray computed tomography (CT) images show that the distribution of water and gas phases in quartzitic sands are fractal. The area and tortuosity fractal dimensions, that quantitatively describe the water and gas distribution in the pores, can be computed from the CT images using the box-counting method. These fractal dimensions are further used to establish a fractal theory based relative permeability model. The proposed model implies that relative gas permeability is expected to increase and relative water permeability slightly decreases even the effective water saturation is unchanged during gas production from hydrate deposits, as hydrate dissociation increases the overall pore diameter and lowers capillarity that allows gas to migrate with less effort.
Hydro-bio-geomechanical properties of hydrate-bearing sediments from Nankai Trough
Marine and Petroleum GeologyJC Santamarina, S Dai, M Terzariol, J Jang, WF Waite, WJ Winters, J Nagao, J Yoneda, Y Konno, T Fujii, K Suzuki
2015
Natural hydrate-bearing sediments from the Nankai Trough, offshore Japan, were studied using the Pressure Core Characterization Tools (PCCTs) to obtain geomechanical, hydrological, electrical, and biological properties under in situ pressure, temperature, and restored effective stress conditions. Measurement results, combined with index-property data and analytical physics-based models, provide unique insight into hydrate-bearing sediments in situ. Tested cores contain some silty-sands, but are predominantly sandy- and clayey-silts. Hydrate saturations Sh range from 0.15 to 0.74, with significant concentrations in the silty-sands. Wave velocity and flexible-wall permeameter measurements on never-depressurized pressure-core sediments suggest hydrates in the coarser-grained zones, the silty-sands where Sh exceeds 0.4, contribute to soil-skeletal stability and are load-bearing. In the sandy- and clayey-silts, where Sh < 0.4, the state of effective stress and stress history are significant factors determining sediment stiffness. Controlled depressurization tests show that hydrate dissociation occurs too quickly to maintain thermodynamic equilibrium, and pressure–temperature conditions track the hydrate stability boundary in pure-water, rather than that in seawater, in spite of both the in situ pore water and the water used to maintain specimen pore pressure prior to dissociation being saline. Hydrate dissociation accompanied with fines migration caused up to 2.4% vertical strain contraction. The first-ever direct shear measurements on never-depressurized pressure-core specimens show hydrate-bearing sediments have higher sediment strength and peak friction angle than post-dissociation sediments, but the residual friction angle remains the same in both cases. Permeability measurements made before and after hydrate dissociation demonstrate that water permeability increases after dissociation, but the gain is limited by the transition from hydrate saturation before dissociation to gas saturation after dissociation. In a proof-of-concept study, sediment microbial communities were successfully extracted and stored under high-pressure, anoxic conditions. Depressurized samples of these extractions were incubated in air, where microbes exhibited temperature-dependent growth rates.
Hydrate morphology: Physical properties of sands with patchy hydrate saturation
Journal of Geophysical ResearchS Dai, JC Santamarina, WF Waite, TJ Kneafsey
2012
The physical properties of gas hydrate‐bearing sediments depend on the volume fraction and spatial distribution of the hydrate phase. The host sediment grain size and the state of effective stress determine the hydrate morphology in sediments; this information can be used to significantly constrain estimates of the physical properties of hydrate‐bearing sediments, including the coarse‐grained sands subjected to high effective stress that are of interest as potential energy resources. Reported data and physical analyses suggest hydrate‐bearing sands contain a heterogeneous, patchy hydrate distribution, whereby zones with 100% pore‐space hydrate saturation are embedded in hydrate‐free sand. Accounting for patchy rather than homogeneous hydrate distribution yields more tightly constrained estimates of physical properties in hydrate‐bearing sands and captures observed physical‐property dependencies on hydrate saturation. For example, numerical modeling results of sands with patchy saturation agree with experimental observation, showing a transition in stiffness starting near the series bound at low hydrate saturations but moving toward the parallel bound at high hydrate saturations. The hydrate‐patch size itself impacts the physical properties of hydrate‐bearing sediments; for example, at constant hydrate saturation, we find that conductivity (electrical, hydraulic and thermal) increases as the number of hydrate‐saturated patches increases. This increase reflects the larger number of conductive flow paths that exist in specimens with many small hydrate‐saturated patches in comparison to specimens in which a few large hydrate saturated patches can block flow over a significant cross‐section of the specimen.
