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Edmund J Fordham - One of the best experts on this subject based on the ideXlab platform.
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nuclear magnetic resonance relaxation and diffusion in the presence of internal gradients the effect of magnetic field strength
Physical Review E, 2010Co-Authors: J Mitchell, T C Chandrasekera, Michael L Johns, L F Gladden, Edmund J FordhamAbstract:It is known that internal magnetic field gradients in Porous materials, caused by susceptibility differences at the solid-fluid interfaces, alter the observed effective Nuclear Magnetic Resonance transverse relaxation times T 2,eff . The internal gradients scale with the strength of the static background magnetic field B o . Here, we acquire data at various magnitudes of B 0 to observe the influence of internal gradients on T 2 -T 2 exchange measurements; the theory discussed and observations made are applicable to any T 2 -T 2 analysis of heterogeneous materials. At high magnetic field strengths, it is possible to observe diffusive exchange between regions of local internal gradient extrema within individual pores. Therefore, the observed exchange pathways are not associated with pore-to-pore exchange. Understanding the significance of internal gradients in transverse relaxation measurements is critical to interpreting these results. We present the example of water in Porous Sandstone rock and offer a guideline to determine whether an observed T 2,eff relaxation time distribution reflects the pore size distribution for a given susceptibility contrast (magnetic field strength) and spin echo separation. More generally, we confirm that for Porous materials T 1 provides a better indication of the pore size distribution than T 2,eff at high magnetic field strengths (B o > 1 T), and demonstrate the data analysis necessary to validate pore size interpretations of T 2,eff measurements.
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nuclear magnetic resonance relaxation and diffusion in the presence of internal gradients the effect of magnetic field strength
Physical Review E, 2010Co-Authors: J Mitchell, T C Chandrasekera, Michael L Johns, L F Gladden, Edmund J FordhamAbstract:It is known that internal magnetic field gradients in Porous materials, caused by susceptibility differences at the solid-fluid interfaces, alter the observed effective Nuclear Magnetic Resonance transverse relaxation times ${T}_{2,\text{eff}}$. The internal gradients scale with the strength of the static background magnetic field ${B}_{0}$. Here, we acquire data at various magnitudes of ${B}_{0}$ to observe the influence of internal gradients on ${T}_{2}\text{\ensuremath{-}}{T}_{2}$ exchange measurements; the theory discussed and observations made are applicable to any ${T}_{2}\text{\ensuremath{-}}{T}_{2}$ analysis of heterogeneous materials. At high magnetic field strengths, it is possible to observe diffusive exchange between regions of local internal gradient extrema within individual pores. Therefore, the observed exchange pathways are not associated with pore-to-pore exchange. Understanding the significance of internal gradients in transverse relaxation measurements is critical to interpreting these results. We present the example of water in Porous Sandstone rock and offer a guideline to determine whether an observed ${T}_{2,\text{eff}}$ relaxation time distribution reflects the pore size distribution for a given susceptibility contrast (magnetic field strength) and spin echo separation. More generally, we confirm that for Porous materials ${T}_{1}$ provides a better indication of the pore size distribution than ${T}_{2,\text{eff}}$ at high magnetic field strengths $({B}_{0}g1\text{ }\text{T})$, and demonstrate the data analysis necessary to validate pore size interpretations of ${T}_{2,\text{eff}}$ measurements.
Ziqiu Xue - One of the best experts on this subject based on the ideXlab platform.
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ultrasonic velocity and attenuation during co2 injection into water saturated Porous Sandstone measurements using difference seismic tomography
Physics of the Earth and Planetary Interiors, 2009Co-Authors: Xinglin Lei, Ziqiu XueAbstract:We undertook laboratory-based seismic measurements with dense sensor array at ultrasonic frequencies during the injection of CO2 into a water-saturated Sandstone specimen. The resulting high-quality seismic data enabled detailed determination of the relative velocity and attenuation coefficient of the compressional wave using difference seismic tomography, which directly inverses time-lapse changes in rock properties from time-lapse changes in observed data. CO2 migration and water displacement were clearly mapped using tomographic images of relative velocity and the attenuation coefficient. The final and largely stabilised volume fraction of CO2 in the pore space of the sample is about 30–40%. On average, the P-velocity fell by 7.5, 12, and 14.5% and the attenuation coefficient Q−1 increased by factors of 3.3, 2.7, and 3.7 as a result of the replacement of water with CO2 during the injection of gaseous, liquid, and supercritical CO2, respectively. As a function of gas saturation, both the velocity and attenuation data are in good agreement with results obtained using the White and Dutta–Ode model for partial saturation, indicating that viscous losses due to fluid diffusion are of significant importance for compressional waves travelling at ultrasonic frequencies in Porous rocks.
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effects of bedding plane on co2 migration and deformation strain in water saturated Porous Sandstone
Greenhouse Gas Control Technologies 7#R##N#Proceedings of the 7th International Conference on Greenhouse Gas Control Technologies 5– September 2004 Va, 2005Co-Authors: Ziqiu Xue, Takashi OhsumiAbstract:Publisher Summary This chapter presents a study with the objectives as follows: (1) to demonstrate the use of cross-well seismic profiling for monitoring the location of carbon dioxide (CO2), (2) to provide a petro-physical basis for such seismic monitoring and its interpretation. Seismic methods have found successful applications in (CO2) geological sequestration. In seismic monitoring applications, the impedance contrast caused by the CO2-water displacement is the physical basis of the response. Velocity changes are significant relative to the ability of seismic methods to detect impedance changes in the order of 5%. Seismic properties depend on mineral compositions of rocks as well as factors such as porosity, fluid content, and in-situ stress and temperature. Interpretation of seismic field data requires a better understanding of the process of CO2-water displacement. There is a practical need to estimate the CO2 mass within the reservoir and predict the long-term behavior of the injected CO2.
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Seismic wave monitoring of CO2 migration in water-saturated Porous Sandstone
Exploration Geophysics, 2004Co-Authors: Ziqiu Xue, Takashi OhsumiAbstract:We have carried out laboratory measurements of P-wave velocity and deformation strain during CO2 injection into a Porous Sandstone sample, in dry and water-saturated conditions. The rock sample was cylindrical, with the axis normal to the bedding plane, and fluid injection was performed from one end. Using a piezoelectric transducer array system, we mapped fluid movement during injection of distilled water into dry Sandstone, and of gaseous, liquid, and supercritical CO2 into a water-saturated sample. The velocity changes caused by water injection ranged from 5.61 to 7.52%. The velocity changes caused by CO2 injection are typically about -6%, and about -10% for injection of supercritical CO2. Such changes in velocity show that the seismic method may be useful in mapping CO2 movement in the subsurface. Strain normal to the bedding plane was greater than strain parallel to the bedding plane during CO2 injection; injection of supercritical CO2 showed a particularly strong effect. Strain changes suggest the possibility of monitoring rock mass deformation by using borehole tiltmeters at geological sequestration sites. We also found differences associated with CO2 phases in velocity and strain changes during injection.
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laboratory measurements of seismic wave velocity by co2 injection in two Porous Sandstones
Greenhouse Gas Control Technologies - 6th International Conference#R##N#Proceedings of the 6th International Conference on Greenhouse Gas Control Tech, 2003Co-Authors: Ziqiu Xue, Takashi Ohsumi, Hitoshi KoideAbstract:This chapter presents a preliminary result of measurements on velocity changes while injecting CO 2 into water-saturated Shirahama and Tako Sandstone. Wave velocity and attenuation in Porous Sandstone are widely studied in fields of reservoir engineering and geo-engineering. Seismic survey provides substantial information concerning positions for new wells and modification of the existing depletion strategy. Cross-well seismic tomography is considered as a promising monitoring method to map the movement of CO 2 in the subsurface. The formation water, which existed in pore spaces within reservoir rocks, will be partially displaced by the injected CO 2 . This process will affect the propagation characteristics of the seismic waves. Seismic properties depend on the mineralogical composition of the rock as well as factors such as porosity, fluid content, and in situ stress. Previous works on effects of CO 2 flooding on seismic wave velocity clearly show that CO 2 flooding caused compressional wave (P-wave) velocities to substantially decrease. Interpretation of seismic monitoring of CO 2 flooding requires an understanding of the effects of pore pressure buildup caused by the CO 2 injection and CO 2 saturation. Experimental studies, such as converting field measurements of wave velocities and attenuations to CO 2 saturation, support the interpretation of the survey results. A series of seismic tomography experiments on Porous Sandstone samples to demonstrate the use of cross-well seismic profiling for monitoring the migration of CO 2 in geological sequestration projects have been conducted.
J Mitchell - One of the best experts on this subject based on the ideXlab platform.
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nuclear magnetic resonance relaxation and diffusion in the presence of internal gradients the effect of magnetic field strength
Physical Review E, 2010Co-Authors: J Mitchell, T C Chandrasekera, Michael L Johns, L F Gladden, Edmund J FordhamAbstract:It is known that internal magnetic field gradients in Porous materials, caused by susceptibility differences at the solid-fluid interfaces, alter the observed effective Nuclear Magnetic Resonance transverse relaxation times T 2,eff . The internal gradients scale with the strength of the static background magnetic field B o . Here, we acquire data at various magnitudes of B 0 to observe the influence of internal gradients on T 2 -T 2 exchange measurements; the theory discussed and observations made are applicable to any T 2 -T 2 analysis of heterogeneous materials. At high magnetic field strengths, it is possible to observe diffusive exchange between regions of local internal gradient extrema within individual pores. Therefore, the observed exchange pathways are not associated with pore-to-pore exchange. Understanding the significance of internal gradients in transverse relaxation measurements is critical to interpreting these results. We present the example of water in Porous Sandstone rock and offer a guideline to determine whether an observed T 2,eff relaxation time distribution reflects the pore size distribution for a given susceptibility contrast (magnetic field strength) and spin echo separation. More generally, we confirm that for Porous materials T 1 provides a better indication of the pore size distribution than T 2,eff at high magnetic field strengths (B o > 1 T), and demonstrate the data analysis necessary to validate pore size interpretations of T 2,eff measurements.
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nuclear magnetic resonance relaxation and diffusion in the presence of internal gradients the effect of magnetic field strength
Physical Review E, 2010Co-Authors: J Mitchell, T C Chandrasekera, Michael L Johns, L F Gladden, Edmund J FordhamAbstract:It is known that internal magnetic field gradients in Porous materials, caused by susceptibility differences at the solid-fluid interfaces, alter the observed effective Nuclear Magnetic Resonance transverse relaxation times ${T}_{2,\text{eff}}$. The internal gradients scale with the strength of the static background magnetic field ${B}_{0}$. Here, we acquire data at various magnitudes of ${B}_{0}$ to observe the influence of internal gradients on ${T}_{2}\text{\ensuremath{-}}{T}_{2}$ exchange measurements; the theory discussed and observations made are applicable to any ${T}_{2}\text{\ensuremath{-}}{T}_{2}$ analysis of heterogeneous materials. At high magnetic field strengths, it is possible to observe diffusive exchange between regions of local internal gradient extrema within individual pores. Therefore, the observed exchange pathways are not associated with pore-to-pore exchange. Understanding the significance of internal gradients in transverse relaxation measurements is critical to interpreting these results. We present the example of water in Porous Sandstone rock and offer a guideline to determine whether an observed ${T}_{2,\text{eff}}$ relaxation time distribution reflects the pore size distribution for a given susceptibility contrast (magnetic field strength) and spin echo separation. More generally, we confirm that for Porous materials ${T}_{1}$ provides a better indication of the pore size distribution than ${T}_{2,\text{eff}}$ at high magnetic field strengths $({B}_{0}g1\text{ }\text{T})$, and demonstrate the data analysis necessary to validate pore size interpretations of ${T}_{2,\text{eff}}$ measurements.
Campanale F. - One of the best experts on this subject based on the ideXlab platform.
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Direct quartz-coesite transformation in shocked Porous Sandstone from Kamil Crater (Egypt)
'Geological Society of America', 2018Co-Authors: Folco L., Mugnaioli E., Gemelli M., Masotta M., Campanale F.Abstract:Coesite, a high-pressure silica polymorph (pressure 3–10 GPa, temperature <3000 K), is a diagnostic feature of shock metamorphism associated with impact cratering on quartz-bearing target rocks. It is preserved as a metastable phase in sedimentary target rocks that experienced peak pressures in excess of ~10 GPa, where it typically occurs as intergranular polycrystalline aggregates of microcrystals embedded in silica glass known as “symplectic regions.” The presence of coesite in the symplectic regions of rocks experiencing shock conditions beyond the limits of the coesite stability field is a controversial issue. Through a combined scanning and transmission electron microscopy and Raman spectroscopy study of shocked quartzarenites from the 45-m-diameter Kamil Crater (southwest Egypt), we show that coesite in symplectic regions forms through direct subsolidus transformation from quartz, in contrast with the prevailing hypothesis for crystalline targets. The quartz-to-coesite transformation takes place during localized shock-wave reverberation at the beginning of the pore collapse process. Complete pore collapse generates the high temperature regimes responsible for the subsequent production of the embedding silica melts, in part at the expense of the previously formed coesite. This work documents the role of pore collapse in producing localized pressure-temperature-time gradients in shocked Porous targets, as predicted by numerical models in the literature
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Direct quartz-coesite transformation in shocked Porous Sandstone from Kamil Crater (Egypt)
'Geological Society of America', 2018Co-Authors: Folco L., Mugnaioli E., Gemelli M., Masotta M., Campanale F.Abstract:Coesite, a high-pressure silica polymorph (pressure 3-10 GPa, temperature
Ellimaria Christodoulos Charalampidou - One of the best experts on this subject based on the ideXlab platform.
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compaction bands in a Porous Sandstone sample with pre induced shear bands
International Workshop on Bifurcation and Degradation in Geomaterials, 2017Co-Authors: Ellimaria Christodoulos Charalampidou, Sergei Stanchits, Georg DresenAbstract:Understanding how different modes of deformation bands may interact at the same rock mass is of crucial importance, since such interaction may affect the flow properties within the reservoir rock. In this work we focus on the compaction band nucleation and evolution within a Porous Sandstone, in which a shear-band has been previously developed. For such a purpose, we performed at the laboratory scale triaxial compression experiments under 20 and 185 MPa confining pressures on a single Bentheim Sandstone specimen. Acoustic Emissions (AE) were recorded throughout all experimental stages. AE hypocentre locations and AE source mechanisms were used to describe the spatiotemporal evolution of the developed deformation bands. The shear band evolution was AE controlled. Shear type sources were the prevailing mechanisms up to the peak stress, whereas, the shear band growth was mainly dominated by compressive type sources. The compaction band nucleated at the tip of the pre-existing shear band and evolved towards the circumference of the specimen. A second compaction band nucleated with increasing axial strain at the top part of the specimen and not far from the already developed shear and compaction bands. The dominant mechanisms during the compaction band initiation and formation were compressive type sources.
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shear enhanced compaction band identification at the laboratory scale using acoustic and full field methods
International Journal of Rock Mechanics and Mining Sciences, 2014Co-Authors: Ellimaria Christodoulos Charalampidou, Sergei Stanchits, Stephen Hall, Gioacchino Viggiani, Helen LewisAbstract:Abstract This paper presents results from the analysis of shear-enhanced compaction bands that developed in a Porous Sandstone during triaxial compression tests at high confining pressures. The analysis uses non-destructive full-field experimental methods: X-ray tomography, 3D-volumetric digital image correlation (DIC) and acoustic emission (AE) monitoring including source mechanisms analysis. The 3D-volumetric DIC measurements reveal that these bands are zones with: a small component of band-parallel slip; a larger component of vertical shortening; compactant volumetric strains; and high maximum shear strains. Low X-ray tomography gray-scale standard deviation values within the bands indicate regions of grain size reduction and grain fragmentation. AE hypocenters detected during loading were concentrated inside these narrow bands and showed predominantly pure and hybrid collapse mechanisms; the latter implies some shear strain and is consistent with the oblique geometry of these bands. The experimental results in general support the hypothesis that laboratory developed shear-enhanced compaction bands, at least those studied here, share more characteristics with compaction bands than with compactant shear-bands; these latter deformation features differ from shear-enhanced compaction bands not only in the mechanical behavior, but also in the kinematics and the grain-scale deformation mechanisms.
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characterization of shear and compaction bands in a Porous Sandstone deformed under triaxial compression
Tectonophysics, 2011Co-Authors: Ellimaria Christodoulos Charalampidou, Sergei Stanchits, Helen Lewis, Stephen Hall, Gioacchino ViggianiAbstract:Abstract The study of localized deformation in Porous Sandstones at the laboratory scale can yield valuable insights into the internal structures and mechanisms of shear zones and compaction bands that might impact on flow at a reservoir scale. Herein, we report results of a laboratory study of shear and compaction band formation in a Porous Sandstone using a range of full-field experimental techniques: acoustic emissions, ultrasonic tomography, X-ray tomography, and 3D volumetric digital image correlation, plus thin section and Scanning Electron Microscope observations. The two main mechanisms involved in shear and compaction band formation, grain breakage (damage) and porosity reduction (compaction), are both well captured by the combination of all these laboratory techniques. The combined use of these techniques demonstrated the processes of shear and compaction band generation and the associated strain components that developed in the laboratory, and potentially also increased understanding of the naturally developed equivalents. The physical mechanisms of shear and compaction involved seem to be similar, but at the laboratory scale they show differences in the proportions and the order of occurrence in time.