Pathegama G Ranjith - Profile on Academia.edu (original) (raw)

Papers by Pathegama G Ranjith

On the correlation between proppant addition strategy and distribution

Natural gas hydrates – Insights into a paradigm-shifting energy resource

Energy reviews, Mar 1, 2023

Water Air and Soil Pollution, Jan 25, 2020

Leaching of phosphorus fertilizer from loosestructured subtropical soils is a major course of agr... more Leaching of phosphorus fertilizer from loosestructured subtropical soils is a major course of agricultural water pollution in southeastern USA. Soil amendments play a major role in the phosphorus retention in soil through different mechanisms. In the present study we tested the effect of two soil amendments; biochar and coal fly ash in immobilizing the soluble phosphorus fertilizer added to sandy Ultisol soils from subtropical USA. Column leaching tests were conducted with Ultisol soil added with biochar (from avocado branch cut biomass) and coal fly ash at 5 tons/ha rate, under simulated rainfall, to collect the leachate over five pore volumes. The leachate was analyzed for the phosphate phosphorus content. In the end, the soil columns were carefully extracted, sectioned and analyzed for the total phosphorus, after acid digestion. Results showed 50% and 6% drop of soluble phosphorus leaching loss in biochar and coal fly ash added soil respectively. Soil amendments have shifted the loosely bound phosphorus into the Ca/Mg bound and Al/Fe/Mn bound pools which are not readily water extractable. Addition of biochar and coal fly ash together showed a synergistic interaction effect in reducing the leaching loss of phosphorus which needs further investigation to understand the exact mechanism.

Energies, Nov 17, 2016

Global energy and material consumption are expected to rise in exponential proportions during the... more Global energy and material consumption are expected to rise in exponential proportions during the next few decades, generating huge demands for deep earth energy (oil/gas) recovery and mineral processing. Under such circumstances, the continuation of existing methods in rock fragmentation in such applications is questionable due to the proven adverse environmental impacts associated with them. In this regard; the possibility of using more environmentally friendly options as Soundless Chemical Demolition Agents (SCDAs) play a vital role in replacing harmful conventional rock fragmentation techniques for gas; oil and mineral recovery. This study reviews up to date research on soundless cracking demolition agent (SCDA) application on rock fracturing including its limitations and strengths, possible applications in the petroleum industry and the possibility of using existing rock fragmentation models for SCDA-based rock fragmentation; also known as fracking. Though the expansive properties of SCDAs are currently used in some demolition works, the poor usage guidelines available reflect the insufficient research carried out on its material's behavior. SCDA is a cementitious powdery substance with quicklime (CaO) as its primary ingredient that expands upon contact with water; which results in a huge expansive pressure if this CaO hydration reaction occurs in a confined condition. So, the mechanism can be used for rock fragmentation by injecting the SCDA into boreholes of a rock mass; where the resulting expansive pressure is sufficient to create an effective fracture network in the confined rock mass around the borehole. This expansive pressure development, however, dependent on many factors, where formation water content creates a negative influence on this due to required greater degree of hydration under greater water contents and temperature creates a positive influence by accelerating the reaction. Having a precise understanding of the fracture propagation mechanisms when using SCDA is important due to the formation of complex fracture networks in rocks. Several models can be found in the literature based on the tangential and radial stresses acting on a rock mass surrounding an SCDA charged borehole. Those fracture models with quasi-static fracturing mechanism that occurs in Mode I type tensile failure show compatibility with SCDA fracturing mechanisms. The effect of borehole diameter, spacing and the arrangement on expansive pressure generation and corresponding fracture network generation is important in the SCDA fracturing process and effective handling of them would pave the way to creating an optimum fracture network in a targeted rock formation. SCDA has many potential applications in unconventional gas and oil recovery and in-situ mining in mineral processing. However, effective utilization of SCDA in such application needs much extensive research on the performance of SCDA with respect to its potential applications, particularly when considering unique issues arising in using SCDA in different applications.

Fired-Siltstone Based Geopolymers for CO2 Sequestration Wells : A Study on the Effect of Curing Temperature

Wellbore integrity during Carbon Dioxide (CO2) storage in deep aquifers is a major problem as the... more Wellbore integrity during Carbon Dioxide (CO2) storage in deep aquifers is a major problem as the currently used well cement will lose its integrity at higher temperatures and eventually leads to CO2 leakage into the atmosphere. Researchers have conducted several studies in order to find a proper well cement material and have tested several types of geopolymers mixing fly ash and different type of cements with an alkaline solution curing in different temperatures. This paper presents a study on geopolymer composites made from fired siltstone, slag as well as alkaline liquid which were cured at temperatures ranging from 23°C to 80°C. Five different types of geopolymer were prepared with ratios of fired siltstone (to 700 oC) and slag as 0:100, 20:80, 30:70, 40:60 and 50:50, separately. After preparing samples with various proportions under different temperatures, the mechanical properties of them were compared. The experimental results reveal that optimum curing temperature range is 50 to 70°C and addition of higher proportion of slag would help geopolymer gain better performance on mechanical strength compared to other geopolymer materials.

Geomechanics and geophysics for geo-energy and geo-resources, Jul 25, 2020

The brittleness of rocks plays an important role in the fracture network fracturing process of un... more The brittleness of rocks plays an important role in the fracture network fracturing process of unconventional oil and gas reservoirs, the drilling efficiency of rock breaking and wall stability, and mining engineering. Rock brittleness has become one of the key parameters in the study of many rock mechanics and related engineering problems. However, there is still no widely accepted definition of brittleness. Although many criteria have been proposed to characterize rock brittleness, their applicability and reliability have yet to be verified. Therefore, brittleness evaluations require further study. In this paper, we divided the rocks under an external load into the unruptured area (body I system) and ruptured area (body II system). We considered that the body I system provided energy for the fracture of the II body. The brittleness of rock is understood as the ability of energy release when a post-peak fracture occurs in the II system. Therefore, the quasi-static energy-balanced equation of a double-body system

Effect of grain size on mineral carbonation coal combustion fly ash for CO2 sequestration

Over the years, there has been a rapid increase in atmospheric CO 2 concentrations, from 280 ppm ... more Over the years, there has been a rapid increase in atmospheric CO 2 concentrations, from 280 ppm in 1850 to 360 ppm in 1998. Therefore, mitigation methods such as carbon sequestration in subsurface reservoirs have been suggested. CO 2 sequestration is attractive, especially in relation to coal, with the additional potential benefit of CH 4 recovery. However, the potential of CO 2 sequestration is not well understood for various types of coals due to important in situ properties of coal. In this study, data from previous studies for coal permeability, density, moisture content, mineral content, vitrinite reflectance, compressive strength and temperature are compared with the CO 2 adsorption results to understand the significance of these in situ coal properties on CO 2 sequestration. To verify the findings, a custom-designed advanced core flooding apparatus is used to simulate the effects of various in situ properties on CO 2 sequestration. This apparatus can test samples of 203 mm in diameter and up to 1000 mm in length. Hence, heterogeneity effects can be understood, as previous CO 2 sequestration-related formulae have been based on coal samples of sizes ranging up to only about 100 mm. However, initially, a reconstituted coal core sample has been used to simplify the heterogeneity effects. Flow rates are estimated by analysing the lag of downstream pressures over time. With the use of a 203-mm-diameter and 816-mm-long reconstituted Victorian brown coal sample, flow rate reductions of 70% and 98% are observed for injection pressures of 2 and 4 MPa, respectively, due to CO 2 injection. This study highlights the appropriateness of a candidate coal reservoir for CO 2 storage in terms of in situ properties.

An experimental study to investigate the effective factors for the performance of coal mass natural cleat system upon CO2 sequestration process in deep coal seams

ABSTRACT

Advances in environmental engineering and green technologies book series, 2018

Shale gas has been considered as an unconventional resource to date due to economics and technica... more Shale gas has been considered as an unconventional resource to date due to economics and technical challenges encountered. Under current circumstances, shale gas has and is receiving increasing attention as it is being quickly known as a viable energy resource. Countries who have been out of the energy game so far have an opportunity to be key players in the same industry. Current enhancement in technology and improved methods for fracking have proven that recovering shale gas is a viable and economically sound option in this century.

Discussions on Correction of Goodman Jack Test

Geotechnical Testing Journal, Jan 12, 2017

The Goodman jack is widely used to measure the deformation modulus of rock in the field. Although... more The Goodman jack is widely used to measure the deformation modulus of rock in the field. Although some corrections have been proposed for the jack in the research literature, the accuracy of the test remains unsatisfactory, and the results of the Goodman jack test are lower than the actual values. Based on the corrections proposed in the literature, we reported on two factors which may lead to a lower value of the Goodman jack test: one was the non-full rock/platen contact when the borehole is under- or over-sized (relative to the standard borehole with a diameter of 76.2 mm), and the other was the upper limitation on the applied hydraulic pressure. First, a numerical simulation was carried out to investigate the impact of the borehole diameter on the rock/platen contact and the calculated rock modulus. The results showed that when there is a deviation of 0.6 mm in the borehole diameter, the calculated rock modulus may be 2 to 5 times lower. Based on the results of numerical simulation, a borehole diameter-related correction is proposed for the tests in under- or over-sized boreholes. Second, to ensure that the rock responds elastically during the test, we analyzed the stress around the borehole, and based on the Mohr-Coulomb and tensile failure criteria, deduced the upper limitation for the applied hydraulic pressure. The results of a case study in a coal mine suggest that the pressure limitation is controlled by the initial stress in the field and the rock strength, and influenced significantly by the loading direction of the jack. Finally, based on the observations in the present research, a new procedure is suggested for the Goodman jack test, which may be helpful in improving the accuracy of in situ testing.

Experimental characterization of time-dependent mechanical behaviours of frac sand at high compressive stresses and implication on long-term proppant conductivity

Geomechanics and Geophysics for Geo-Energy and Geo-Resources

Abstract This paper experimentally examines the time-dependent mechanical behaviours of frac sand... more Abstract This paper experimentally examines the time-dependent mechanical behaviours of frac sand at high compressive stresses. A series of instant and sustained one-dimensional compression tests was performed on Jordan sand, White sand, and Genoa sand, and three grain size distributions for each frac sand were tested. The acoustic emission events related to sand crushing were monitored by piezoelectric sensors for understanding sand breakage during compression. The results show that Genoa sand with 25% weaker anorthite mineral grains show much more grain breakage and higher plastic and creep strains at high compressive stresses than the pure quartz Jordan and White sand. Wider grain size distributions tend to result in larger plastic strains than narrower size distributions but provide better crushing resistance and smaller creep deformation. Cyclic and creep load stages only slightly increase grain breakage compared with instant loads, but result in higher plastic and creep strains. Two creep stages were found in the time-dependent deformation of sand and can be satisfactorily depicted with the Riemann–Liouville fractional calculus model at different stress levels, with sand’s fractional derivative of increases from 0.28 to 0.35 as sand grains are gradually crushed. Lower viscosity coefficients are found in Genoa (~ 15e4 MPa*s) than White and Jordan sand (> 20e4 MPa*s). The time-dependent deformation of sand proppant has a significant implication on the long-term conductivity of sand packs, which can reduce the hydraulic conductivity by about 40%–90% after a one-year duration. The results warrant considering frac sand’s long-term deformation when choosing frac sand as proppants in hydraulic fracturing. Article Highlights Weaker Genoa sand shows 50–150% higher plastic and creep strains than Jordan and White sand at high compression. Wider grain size distributions result in larger plastic but smaller strains creep in sand at sustained loads. Creep strain is depicted by fractional calculus with an increased derivative from 0.28 to 0.35 as sand is crushed.

The Influence of Confining Stresses on Formation Kinetics of Methane Gas Hydrates

Fuel, 2022

Tensile Behaviors of Granite: Grain Scale Cracking and Fracture Process Zone

Uncovering the creep deformation mechanism of rock-forming minerals using nanoindentation

International Journal of Mining Science and Technology, 2021

Soil and plant growth response and trace elements accumulation in sweet corn and snow pea grown under fresh and carbonated coal fly ash amendment

Agronomy Journal, 2021

Mechanical properties of α-quartz using nanoindentation tests and molecular dynamics simulations

International Journal of Rock Mechanics and Mining Sciences, 2021

Abstract Understanding the mechanical properties of α-quartz is of vital importance to rock engin... more Abstract Understanding the mechanical properties of α-quartz is of vital importance to rock engineering because α-quartz is the main component of igneous, metamorphic and sedimentary rocks. Molecular dynamics simulations (MDs) of nanoindentation tests on α-quartz were performed to investigate the effects of indenter tip radius and penetration depth on the mechanical properties of α-quartz. Indentation load-penetration depth (P-h) curves were plotted, from which Reduced Young’s modulus ( E r ) , hardness ( H ) were obtained and these mechanical parameters were then compared with the laboratory nanoindentation results. The mechanical results obtained from MDs are in good agreement with the experimental values. It can be found that E r and H increase with indentation depth at shallow contact depth while they decrease with indenter tip size. To the authors’ knowledge, this is the first MDs of nanoindentation test of hard rock-forming minerals reported and we believe that this study can shed light on the precise measurement of the mechanical properties of rock minerals at micro- and nano-scales.

E3S Web of Conferences, 2020

During CO2 injection into deep saline aquifers, the overlying caprock may be subjected to geochem... more During CO2 injection into deep saline aquifers, the overlying caprock may be subjected to geochemical reactions which can alter the leakage pathways for injected CO2. Thus, it is crucial to identify the supercritical CO2 (scCO2) flow behaviour via fractures in caprock and its permeability to estimate the permanence of injected CO2. The objective of this study is to find the effect of scCO2 flow on fractured caprock permeability. A fractured siltstone sample was saturated in deionized water and conducted scCO2 permeability tests using a high-precision advanced core flooding apparatus under different injection pressures and confinements. Next, the siltstone sample was saturated in 10% w/w NaCl brine and conduced scCO2 permeability tests as described earlier. The results show that the brine-saturated sample has low permeability compared to water-saturated siltstone sample. The reason would be the deposition of evaporites during scCO2 flow through the fractured sample. This is known as ...

Computational Materials Science, 2020

In this article, a series of molecular dynamics (MD) simulations were performed to investigate th... more In this article, a series of molecular dynamics (MD) simulations were performed to investigate the impacts of indentation size, grain size and temperature on the mechanical properties of polycrystalline α-quartz under quasi-static nanoindentation with conical indenter. Results from MD simulations show that the hardness and Young's modulus are more sensitive to the temperature and penetration depth than grain size. Von Mises shear strain and the volumetric strain were calculated to depict the plastic deformation and it was found that plastic deformation becomes more dominate at higher temperatures and indentation sizes for polycrystalline α-quartz. The deformation mechanism is dominated by the grain boundary sliding instead of intragranular dislocation control at small grain size (<10 nm). This work enriches the atomic-level understanding the mechanical properties of α-quartz under nanoindentation tests, which helps to uncover the mechanism of polycrystalline solids breakage and deformation under various conditions.

Water and gas flows through fractured granite

On the correlation between proppant addition strategy and distribution

Natural gas hydrates – Insights into a paradigm-shifting energy resource

Energy reviews, Mar 1, 2023

Water Air and Soil Pollution, Jan 25, 2020

Leaching of phosphorus fertilizer from loosestructured subtropical soils is a major course of agr... more Leaching of phosphorus fertilizer from loosestructured subtropical soils is a major course of agricultural water pollution in southeastern USA. Soil amendments play a major role in the phosphorus retention in soil through different mechanisms. In the present study we tested the effect of two soil amendments; biochar and coal fly ash in immobilizing the soluble phosphorus fertilizer added to sandy Ultisol soils from subtropical USA. Column leaching tests were conducted with Ultisol soil added with biochar (from avocado branch cut biomass) and coal fly ash at 5 tons/ha rate, under simulated rainfall, to collect the leachate over five pore volumes. The leachate was analyzed for the phosphate phosphorus content. In the end, the soil columns were carefully extracted, sectioned and analyzed for the total phosphorus, after acid digestion. Results showed 50% and 6% drop of soluble phosphorus leaching loss in biochar and coal fly ash added soil respectively. Soil amendments have shifted the loosely bound phosphorus into the Ca/Mg bound and Al/Fe/Mn bound pools which are not readily water extractable. Addition of biochar and coal fly ash together showed a synergistic interaction effect in reducing the leaching loss of phosphorus which needs further investigation to understand the exact mechanism.

Energies, Nov 17, 2016

Global energy and material consumption are expected to rise in exponential proportions during the... more Global energy and material consumption are expected to rise in exponential proportions during the next few decades, generating huge demands for deep earth energy (oil/gas) recovery and mineral processing. Under such circumstances, the continuation of existing methods in rock fragmentation in such applications is questionable due to the proven adverse environmental impacts associated with them. In this regard; the possibility of using more environmentally friendly options as Soundless Chemical Demolition Agents (SCDAs) play a vital role in replacing harmful conventional rock fragmentation techniques for gas; oil and mineral recovery. This study reviews up to date research on soundless cracking demolition agent (SCDA) application on rock fracturing including its limitations and strengths, possible applications in the petroleum industry and the possibility of using existing rock fragmentation models for SCDA-based rock fragmentation; also known as fracking. Though the expansive properties of SCDAs are currently used in some demolition works, the poor usage guidelines available reflect the insufficient research carried out on its material's behavior. SCDA is a cementitious powdery substance with quicklime (CaO) as its primary ingredient that expands upon contact with water; which results in a huge expansive pressure if this CaO hydration reaction occurs in a confined condition. So, the mechanism can be used for rock fragmentation by injecting the SCDA into boreholes of a rock mass; where the resulting expansive pressure is sufficient to create an effective fracture network in the confined rock mass around the borehole. This expansive pressure development, however, dependent on many factors, where formation water content creates a negative influence on this due to required greater degree of hydration under greater water contents and temperature creates a positive influence by accelerating the reaction. Having a precise understanding of the fracture propagation mechanisms when using SCDA is important due to the formation of complex fracture networks in rocks. Several models can be found in the literature based on the tangential and radial stresses acting on a rock mass surrounding an SCDA charged borehole. Those fracture models with quasi-static fracturing mechanism that occurs in Mode I type tensile failure show compatibility with SCDA fracturing mechanisms. The effect of borehole diameter, spacing and the arrangement on expansive pressure generation and corresponding fracture network generation is important in the SCDA fracturing process and effective handling of them would pave the way to creating an optimum fracture network in a targeted rock formation. SCDA has many potential applications in unconventional gas and oil recovery and in-situ mining in mineral processing. However, effective utilization of SCDA in such application needs much extensive research on the performance of SCDA with respect to its potential applications, particularly when considering unique issues arising in using SCDA in different applications.

Fired-Siltstone Based Geopolymers for CO2 Sequestration Wells : A Study on the Effect of Curing Temperature

Wellbore integrity during Carbon Dioxide (CO2) storage in deep aquifers is a major problem as the... more Wellbore integrity during Carbon Dioxide (CO2) storage in deep aquifers is a major problem as the currently used well cement will lose its integrity at higher temperatures and eventually leads to CO2 leakage into the atmosphere. Researchers have conducted several studies in order to find a proper well cement material and have tested several types of geopolymers mixing fly ash and different type of cements with an alkaline solution curing in different temperatures. This paper presents a study on geopolymer composites made from fired siltstone, slag as well as alkaline liquid which were cured at temperatures ranging from 23°C to 80°C. Five different types of geopolymer were prepared with ratios of fired siltstone (to 700 oC) and slag as 0:100, 20:80, 30:70, 40:60 and 50:50, separately. After preparing samples with various proportions under different temperatures, the mechanical properties of them were compared. The experimental results reveal that optimum curing temperature range is 50 to 70°C and addition of higher proportion of slag would help geopolymer gain better performance on mechanical strength compared to other geopolymer materials.

Geomechanics and geophysics for geo-energy and geo-resources, Jul 25, 2020

The brittleness of rocks plays an important role in the fracture network fracturing process of un... more The brittleness of rocks plays an important role in the fracture network fracturing process of unconventional oil and gas reservoirs, the drilling efficiency of rock breaking and wall stability, and mining engineering. Rock brittleness has become one of the key parameters in the study of many rock mechanics and related engineering problems. However, there is still no widely accepted definition of brittleness. Although many criteria have been proposed to characterize rock brittleness, their applicability and reliability have yet to be verified. Therefore, brittleness evaluations require further study. In this paper, we divided the rocks under an external load into the unruptured area (body I system) and ruptured area (body II system). We considered that the body I system provided energy for the fracture of the II body. The brittleness of rock is understood as the ability of energy release when a post-peak fracture occurs in the II system. Therefore, the quasi-static energy-balanced equation of a double-body system

Effect of grain size on mineral carbonation coal combustion fly ash for CO2 sequestration

Over the years, there has been a rapid increase in atmospheric CO 2 concentrations, from 280 ppm ... more Over the years, there has been a rapid increase in atmospheric CO 2 concentrations, from 280 ppm in 1850 to 360 ppm in 1998. Therefore, mitigation methods such as carbon sequestration in subsurface reservoirs have been suggested. CO 2 sequestration is attractive, especially in relation to coal, with the additional potential benefit of CH 4 recovery. However, the potential of CO 2 sequestration is not well understood for various types of coals due to important in situ properties of coal. In this study, data from previous studies for coal permeability, density, moisture content, mineral content, vitrinite reflectance, compressive strength and temperature are compared with the CO 2 adsorption results to understand the significance of these in situ coal properties on CO 2 sequestration. To verify the findings, a custom-designed advanced core flooding apparatus is used to simulate the effects of various in situ properties on CO 2 sequestration. This apparatus can test samples of 203 mm in diameter and up to 1000 mm in length. Hence, heterogeneity effects can be understood, as previous CO 2 sequestration-related formulae have been based on coal samples of sizes ranging up to only about 100 mm. However, initially, a reconstituted coal core sample has been used to simplify the heterogeneity effects. Flow rates are estimated by analysing the lag of downstream pressures over time. With the use of a 203-mm-diameter and 816-mm-long reconstituted Victorian brown coal sample, flow rate reductions of 70% and 98% are observed for injection pressures of 2 and 4 MPa, respectively, due to CO 2 injection. This study highlights the appropriateness of a candidate coal reservoir for CO 2 storage in terms of in situ properties.

An experimental study to investigate the effective factors for the performance of coal mass natural cleat system upon CO2 sequestration process in deep coal seams

ABSTRACT

Advances in environmental engineering and green technologies book series, 2018

Shale gas has been considered as an unconventional resource to date due to economics and technica... more Shale gas has been considered as an unconventional resource to date due to economics and technical challenges encountered. Under current circumstances, shale gas has and is receiving increasing attention as it is being quickly known as a viable energy resource. Countries who have been out of the energy game so far have an opportunity to be key players in the same industry. Current enhancement in technology and improved methods for fracking have proven that recovering shale gas is a viable and economically sound option in this century.

Discussions on Correction of Goodman Jack Test

Geotechnical Testing Journal, Jan 12, 2017

The Goodman jack is widely used to measure the deformation modulus of rock in the field. Although... more The Goodman jack is widely used to measure the deformation modulus of rock in the field. Although some corrections have been proposed for the jack in the research literature, the accuracy of the test remains unsatisfactory, and the results of the Goodman jack test are lower than the actual values. Based on the corrections proposed in the literature, we reported on two factors which may lead to a lower value of the Goodman jack test: one was the non-full rock/platen contact when the borehole is under- or over-sized (relative to the standard borehole with a diameter of 76.2 mm), and the other was the upper limitation on the applied hydraulic pressure. First, a numerical simulation was carried out to investigate the impact of the borehole diameter on the rock/platen contact and the calculated rock modulus. The results showed that when there is a deviation of 0.6 mm in the borehole diameter, the calculated rock modulus may be 2 to 5 times lower. Based on the results of numerical simulation, a borehole diameter-related correction is proposed for the tests in under- or over-sized boreholes. Second, to ensure that the rock responds elastically during the test, we analyzed the stress around the borehole, and based on the Mohr-Coulomb and tensile failure criteria, deduced the upper limitation for the applied hydraulic pressure. The results of a case study in a coal mine suggest that the pressure limitation is controlled by the initial stress in the field and the rock strength, and influenced significantly by the loading direction of the jack. Finally, based on the observations in the present research, a new procedure is suggested for the Goodman jack test, which may be helpful in improving the accuracy of in situ testing.

Experimental characterization of time-dependent mechanical behaviours of frac sand at high compressive stresses and implication on long-term proppant conductivity

Geomechanics and Geophysics for Geo-Energy and Geo-Resources

Abstract This paper experimentally examines the time-dependent mechanical behaviours of frac sand... more Abstract This paper experimentally examines the time-dependent mechanical behaviours of frac sand at high compressive stresses. A series of instant and sustained one-dimensional compression tests was performed on Jordan sand, White sand, and Genoa sand, and three grain size distributions for each frac sand were tested. The acoustic emission events related to sand crushing were monitored by piezoelectric sensors for understanding sand breakage during compression. The results show that Genoa sand with 25% weaker anorthite mineral grains show much more grain breakage and higher plastic and creep strains at high compressive stresses than the pure quartz Jordan and White sand. Wider grain size distributions tend to result in larger plastic strains than narrower size distributions but provide better crushing resistance and smaller creep deformation. Cyclic and creep load stages only slightly increase grain breakage compared with instant loads, but result in higher plastic and creep strains. Two creep stages were found in the time-dependent deformation of sand and can be satisfactorily depicted with the Riemann–Liouville fractional calculus model at different stress levels, with sand’s fractional derivative of increases from 0.28 to 0.35 as sand grains are gradually crushed. Lower viscosity coefficients are found in Genoa (~ 15e4 MPa*s) than White and Jordan sand (> 20e4 MPa*s). The time-dependent deformation of sand proppant has a significant implication on the long-term conductivity of sand packs, which can reduce the hydraulic conductivity by about 40%–90% after a one-year duration. The results warrant considering frac sand’s long-term deformation when choosing frac sand as proppants in hydraulic fracturing. Article Highlights Weaker Genoa sand shows 50–150% higher plastic and creep strains than Jordan and White sand at high compression. Wider grain size distributions result in larger plastic but smaller strains creep in sand at sustained loads. Creep strain is depicted by fractional calculus with an increased derivative from 0.28 to 0.35 as sand is crushed.

The Influence of Confining Stresses on Formation Kinetics of Methane Gas Hydrates

Fuel, 2022

Tensile Behaviors of Granite: Grain Scale Cracking and Fracture Process Zone

Uncovering the creep deformation mechanism of rock-forming minerals using nanoindentation

International Journal of Mining Science and Technology, 2021

Soil and plant growth response and trace elements accumulation in sweet corn and snow pea grown under fresh and carbonated coal fly ash amendment

Agronomy Journal, 2021

Mechanical properties of α-quartz using nanoindentation tests and molecular dynamics simulations

International Journal of Rock Mechanics and Mining Sciences, 2021

Abstract Understanding the mechanical properties of α-quartz is of vital importance to rock engin... more Abstract Understanding the mechanical properties of α-quartz is of vital importance to rock engineering because α-quartz is the main component of igneous, metamorphic and sedimentary rocks. Molecular dynamics simulations (MDs) of nanoindentation tests on α-quartz were performed to investigate the effects of indenter tip radius and penetration depth on the mechanical properties of α-quartz. Indentation load-penetration depth (P-h) curves were plotted, from which Reduced Young’s modulus ( E r ) , hardness ( H ) were obtained and these mechanical parameters were then compared with the laboratory nanoindentation results. The mechanical results obtained from MDs are in good agreement with the experimental values. It can be found that E r and H increase with indentation depth at shallow contact depth while they decrease with indenter tip size. To the authors’ knowledge, this is the first MDs of nanoindentation test of hard rock-forming minerals reported and we believe that this study can shed light on the precise measurement of the mechanical properties of rock minerals at micro- and nano-scales.

E3S Web of Conferences, 2020

During CO2 injection into deep saline aquifers, the overlying caprock may be subjected to geochem... more During CO2 injection into deep saline aquifers, the overlying caprock may be subjected to geochemical reactions which can alter the leakage pathways for injected CO2. Thus, it is crucial to identify the supercritical CO2 (scCO2) flow behaviour via fractures in caprock and its permeability to estimate the permanence of injected CO2. The objective of this study is to find the effect of scCO2 flow on fractured caprock permeability. A fractured siltstone sample was saturated in deionized water and conducted scCO2 permeability tests using a high-precision advanced core flooding apparatus under different injection pressures and confinements. Next, the siltstone sample was saturated in 10% w/w NaCl brine and conduced scCO2 permeability tests as described earlier. The results show that the brine-saturated sample has low permeability compared to water-saturated siltstone sample. The reason would be the deposition of evaporites during scCO2 flow through the fractured sample. This is known as ...

Computational Materials Science, 2020

In this article, a series of molecular dynamics (MD) simulations were performed to investigate th... more In this article, a series of molecular dynamics (MD) simulations were performed to investigate the impacts of indentation size, grain size and temperature on the mechanical properties of polycrystalline α-quartz under quasi-static nanoindentation with conical indenter. Results from MD simulations show that the hardness and Young's modulus are more sensitive to the temperature and penetration depth than grain size. Von Mises shear strain and the volumetric strain were calculated to depict the plastic deformation and it was found that plastic deformation becomes more dominate at higher temperatures and indentation sizes for polycrystalline α-quartz. The deformation mechanism is dominated by the grain boundary sliding instead of intragranular dislocation control at small grain size (<10 nm). This work enriches the atomic-level understanding the mechanical properties of α-quartz under nanoindentation tests, which helps to uncover the mechanism of polycrystalline solids breakage and deformation under various conditions.

Water and gas flows through fractured granite

Rock mass strength is the most important single parameter required for stability analyses of rock... more Rock mass strength is the most important single parameter required for stability analyses of rock slopes and many other designs of structures in or on rock masses. However, the precise estimation of rock mass strength is extremely difficult due to its heterogeneous nature induced by the presence of joints. Rock mechanical behaviour is greatly influenced by the geometrical properties of the joints, such as their orientation, persistence, surface roughness and degree of interconnectivity. In addition, different hydro-geological conditions can have marked influences on jointed rock behaviour. The main objective of this thesis is to investigate the influences of various joint geometrical properties on the hydro-mechanical behaviour of jointed rock masses. Experimental, numerical and theoretical investigations were carried out to achieve this objective.

Energy Conference in 2016- september 28th and 29th September

The International Conference on Geomechanics, Geo-energy and Geo-resources will be held at Monash... more The International Conference on Geomechanics, Geo-energy and Geo-resources will be held at Monash University (Australia) from 28th to 29th September 2016.

This conference is aimed at promoting discussion of strategies to address challenges in developing geo-energy and geo-resources extraction, and greenhouse mitigation measures through deep earth from the perspective of geomechanics and geophysics.