Jongwon Jung

Hydrate adhesive and tensile strengths

The physical properties of hydrate-bearing sediments depend on the interaction between hydrates and minerals. In particular, hydrates prefer to nucleate on mineral surfaces, therefore, the hydrate-mineral adhesive strength and the tensile strength of the hydrate mass itself affect the mechanical response of hydrate-bearing sediments. In this study, ice and hydrates made with various guest molecules (CO2, CH4, and THF) are formed between mica and calcite substrates. Adhesive and tensile strengths are measured by applying an external pull-out force. Results show that tensile failure occurs in CO2 and CH4 hydrates when calcite is the substrate, while ice and all hydrates exhibit adhesive failure on mica. The debonding strength is higher when calcite substrates are involved rather than mica substrates. A nominal pull-out strength of 0.15 ± 0.03 MPa can be adopted for mechanical analyses of hydrate-bearing sediments.

CH4‐CO2 replacement in hydrate‐bearing sediments: A pore‐scale study

The injection of CO2 into CH4 hydrate-bearing sediments causes the release of CH4 and the formation of CO2 hydrate within the CH4 hydrate stability field. CH4-CO2 replacement allows for the recovery of an energy source, CH4, while trapping CO2. In this study, we monitor pore-scale changes in electrical resistance and relative stiffness during CH4 hydrate formation, CH4-CO2 replacement, and hydrate dissociation; experiments are also observed using high-resolution time-lapsed photography. Results show that CH4-CO2 replacement occurs locally and gradually so that the overall hydrate mass remains solid and no stiffness loss should be expected at the sediment scale. Other experimental results confirm the slow diffusion of CH4 through the hydrate shell that forms between water and gas; this may allow for the coexistence of gas-hydrate-water phases for long periods of time.

Characterization of a Polyacrylamide Solution Used for Remediation of Petroleum Contaminated Soils

Biopolymers are viewed as effective and eco-friendly agents in soil modification. This study focuses on the wettability analysis of polyacrylamide (PAM) solutions for soil remediation. The contact angle, surface tension, and viscosity of PAM solutions were experimentally evaluated in air- and decane-biopolymer solution systems. Furthermore, a micromodel was used to investigate the pore-scale displacement phenomena during the injection of the PAM solution in decane and or air saturated pores. The contact angle of the PAM solution linearly increases with increasing concentration in air but not in decane. The surface tension between the PAM solution and air decreases at increasing concentration. The viscosity of the PAM solution is highly dependent on the concentration of the solution, shear rate, and temperature. Low flow rate and low concentration result in a low displacement ratio level, which is defined as the volume ratio between the injected and the defended fluids in the pores. The displacement ratio is higher for PAM solutions than distilled water; however, a higher concentration does not necessarily guarantees a higher displacement ratio. Soil remediation could be conducted cost-efficiently at high flow rates but with moderate concentration levels.

Thermal Properties of Fly Ashes and Biomass Ashes Including Wood Bagasse Ashes and Sugarcane Bagasse Ashes

AbstractMostly disposed without treatment, fly and biomass ashes have been a challenge that threatens the environment. To use them as geoenvironmental materials for thermal insulating purposes, a fundamental studying of thermal property of the pure ashes is crucial. In this study, thermal conductivities of fly (class C and F) and biomass ashes (sugarcane bagasse and wood) are studied at dry, saturated, and partial saturated conditions under different effective stresses. Moreover, silica sand and kaolinite are used for comparison. The results show that thermal conductivity dramatically increases with effective stress in dry condition, but less increases in saturated condition. Providing partial-saturated conditions, a substantial increase of thermal conductivity is observed with the degree of saturation, which shows a good consistency with an empirical fitting model using thermal conductivities of minerals of dry and saturated materials. Fly ash class C is cemented by reacting with water that causes therma...

Carbon Geological Storage: Coupled Processes, Engineering and Monitoring

Abstract Today’s energy concerns reflect the large anticipated increase in demand within the next generation, the current dependency on fossil fuels and climate implications, the geographic mismatch between resources and demand, and the disparity in associated time scales. The long-term geological storage of vast quantities of CO2 is a relatively new scientific and technological challenge, plagued with underlying coupled hydro-chemo-mechanical processes and potential emergent phenomena. Processes include: capillarity, density and viscous effects on flow; acidification, mineral dissolution, and ensuing changes in permeability; phase transformations (and CO2-CH4 exchange in hydrates); and stress changes. These processes are involved in the analysis of CO2 storage in saline aquifers, coal seams, depleted reservoirs, and in clathrates. Furthermore, the understanding of underlying processes guides monitoring (active: seismic and electromagnetic; passive: seismic, deformation, thermal) and may lead to improved efficiency and leakage-sealing strategies. Dimensionless ratios help identify the domain for the various dominant processes that govern CO2 geo-storage.

Gas Driven Fracture During Gas Production Using 3D Synchrotron Computed Tomography

During methane gas production from hydrate bearing sandy sediments, fine particles can migrate or clog the pores of sediments. Fines clogging induces a change in pressure gradient which affects the gas flow pattern and might induce gas driven fracture. A fundamental understanding of these phenomena is needed to enhance gas production strategies. Effects of fines migration and clogging on gas flow path and gas driven fracture were studied for Carbon Dioxide (CO2) using 3D Synchrotron Micro-computed Tomography (SMT). Multiphase flow experiments were conducted on brine saturated uniform F75 silica sand mixed with kaolinite at different percentages by weight (2%, 4%, and 6%). Sand-fines mixtures were deposited into a small acrylic cylinder that has two ports; one connected to a flow pump to withdraw the brine solution and the other one was used to inject CO2 gas at a constant pressure (4 psi). The gas migrated through percolation with no major particle displacement of sand for low fines concentration (2% and 4%). Moreover, gas driven fracture was observed for higher fines content. Fines were observed to clog the pores near the CO2-brine boundary interface. SMT is considered to be a powerful tool that can be used to monitor and visualize fines clogging and the flow of gas through sandy sediments.

Variation of Contact Angles in Brine/CO2/Mica System considering Short-Term Geological CO2 Sequestration Condition

Geological CO2 sequestration has been proposed as an effective solution to mitigate excessive human-emitted CO2 in atmosphere. Knowledge of immiscible two-phase flow of CO2-water/brine is necessary to evaluate the efficiency and safety of geological storage sites. Among forces dominating fluid flow, capillary pressure is highly important because of high uncertainty in measurement due to ambiguous wettability behavior of geomaterials. In particular, time-dependent wettability of geomaterials is of interest for predicting short-term performance of the storage site. After injection of CO2 into an aquifer, both the CO2 and water/brine in rocks pores are unsaturated and tend to dissolve into each other. Present study investigates the variation of contact angle on mica sheet using a captive bubble method at a wide range of pressures and salinities under unsaturated condition. Our results showed a general increase of contact angle with time. Comparison of unsaturated contact angle with previous results in the literature showed a wide span of wettability behavior, ranging from receding to advancing contact angle values reported in the literature. The observed decrease in wettability by time due to heterogeneity and pinning effect of triple line can jeopardize the safety of geological carbon sequestration projects in short-term after injection of CO2.

Coefficient of Subgrade Reaction for the Permeable Block and Base System at Korea GI and LID Center

The Permeable block pavement is one of the representative Low Impact Development (LID) techniques for innovative water management based on systems that can infiltrate usually over the surface. The material of each layer in permeable block pavements is often comprised of a granular material with very high porosity not like conventional pavements. However, unlike conventional pavements, researches on structural characteristics of permeable block pavement is insufficient yet. Therefore, in this study, as part of study to understand the structural characteristics of permeable block pavement and open graded aggregate that is used as base material of permeable block pavement, plate load test was carried out on two different pavement sites, site M and N. Site M is aggregate base sites and site N is permeable block pavement site. Based on the relationship between load and settlement that is obtained from the test, coefficient of subgrade reaction (k) was calculated. Through the relationship between load-settlement and k, structural characteristics were evaluated according to material differences of the pavements.

Small Strain Stiffness of Unsaturated Sands Containing a Polyacrylamide Solution

Sand improvements using organic agents have shown promising results. Polyacrylamide is one possible organic agent, which has been shown to influence the shear strength, stiffness, soil remediation, and erosion resistance of geomaterials. In this study, we explored the shear wave velocity (S-wave) and water retention curves of unsaturated sands containing polyacrylamide solutions. The shear wave velocity was measured during the water retention curve measurement tests according to the variation of the degree of saturation. The experimental setup was verified through comparison of the measured water retention curves with the published data. The results show that (1) the S-wave velocity of saturated sands increases with polyacrylamide concentration; (2) as the degree of saturation decreases, the S-wave velocity increases; (3) near the residual water (or polyacrylamide solution) saturation, the S-wave velocity increases dramatically; (4) as the degree of saturation decreases, the S-wave velocity at unsaturated conditions increases with any given water (or polyacrylamide solution) saturation, like the water retention curves; (5) the S-wave velocity increases with the increase in capillary pressure; and (6) the predicted S-wave velocity at a given degree of saturation is slightly overestimated, and the modification of the equation is required.