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Beatriz Quintal - One of the best experts on this subject based on the ideXlab platform.
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seismic attenuation in partially saturated berea Sandstone submitted to a range of confining pressures
Journal of Geophysical Research, 2016Co-Authors: Samuel Chapman, Nicola Tisato, Beatriz Quintal, Klaus HolligerAbstract:Using the forced oscillation method, we measure the extensional-mode attenuation and Young's modulus of a Berea Sandstone Sample at seismic frequencies (0.5–50 Hz) for varying levels of water saturation (~0–100%) and confining pressures (2–25 MPa). Attenuation is negligible for dry conditions and saturation levels <80%. For saturation levels between ~91% and ~100%, attenuation is significant and frequency dependent in the form of distinct bell-shaped curves having their maxima between 1 and 20 Hz. Increasing saturation causes an increase of the overall attenuation magnitude and a shift of its peak to lower frequencies. On the other hand, increasing the confining pressure causes a reduction in the attenuation magnitude and a shift of its peak to higher frequencies. For saturation levels above ~98%, the fluid pressure increases with increasing confining pressure. When the fluid pressure is high enough to ensure full water saturation of the Sample, attenuation becomes negligible. A second series of comparable experiments reproduces these results satisfactorily. Based on a qualitative analysis of the data, the frequency-dependent attenuation meets the theoretical predictions of mesoscopic wave-induced fluid flow (WIFF) in response to a heterogeneous water distribution in the pore space, so-called patchy saturation. These results show that mesoscopic WIFF can be an important source of seismic attenuation at reservoir conditions.
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laboratory measurements of seismic wave attenuation in berea Sandstone as a function of water saturation and confining pressure
Seg Technical Program Expanded Abstracts, 2015Co-Authors: Samuel Chapman, Nicola Tisato, Beatriz Quintal, Klaus HolligerAbstract:We measure extensional-mode attenuation and dynamic Young’s modulus on a Berea Sandstone Sample at seismic frequencies (0.5-50 Hz). The results show a dependence of attenuation with frequency, water saturation and confining pressure. For water saturation levels above 80%, we observe a frequency-dependent bell-shaped attenuation curve with a peak between 1 and 20 Hz. For dry conditions, attenuation is very low and approximately frequencyindependent. Increasing the confining pressure on the Sample causes a reduction of the overall magnitude of the attenuation. The results indicate that the frequencydependent attenuation can be attributed to mesoscopic wave-induced fluid flow (WIFF) caused by heterogeneities in water saturation.
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measurements of seismic attenuation and transient fluid pressure in partially saturated berea Sandstone evidence of fluid flow on the mesoscopic scale
Geophysical Journal International, 2013Co-Authors: Nicola Tisato, Beatriz QuintalAbstract:S U M M A R Y A novel laboratory technique is proposed to investigate wave-induced fluid flow on the mesoscopic scale as a mechanism for seismic attenuation in partially saturated rocks. This technique combines measurements of seismic attenuation in the frequency range from 1 to 100 Hz with measurements of transient fluid pressure as a response of a step stress applied on top of the Sample. We used a Berea Sandstone Sample partially saturated with water. The laboratory results suggest that wave-induced fluid flow on the mesoscopic scale is dominant in partially saturated Samples. A 3-D numerical model representing the Sample was used to verify the experimental results. Biot’s equations of consolidation were solved with the finite-element method. Wave-induced fluid flow on the mesoscopic scale was the only attenuation mechanism accounted for in the numerical solution. The numerically calculated transient fluid pressure reproduced the laboratory data. Moreover, the numerically calculated attenuation, superposed to the frequency-independent matrix anelasticity, reproduced the attenuation measured in the laboratory in the partially saturated Sample. This experimental—numerical fit demonstrates that wave-induced fluid flow on the mesoscopic scale and matrix anelasticity are the dominant mechanisms for seismic attenuation in partially saturated Berea Sandstone.
Nicola Tisato - One of the best experts on this subject based on the ideXlab platform.
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seismic attenuation in partially saturated berea Sandstone submitted to a range of confining pressures
Journal of Geophysical Research, 2016Co-Authors: Samuel Chapman, Nicola Tisato, Beatriz Quintal, Klaus HolligerAbstract:Using the forced oscillation method, we measure the extensional-mode attenuation and Young's modulus of a Berea Sandstone Sample at seismic frequencies (0.5–50 Hz) for varying levels of water saturation (~0–100%) and confining pressures (2–25 MPa). Attenuation is negligible for dry conditions and saturation levels <80%. For saturation levels between ~91% and ~100%, attenuation is significant and frequency dependent in the form of distinct bell-shaped curves having their maxima between 1 and 20 Hz. Increasing saturation causes an increase of the overall attenuation magnitude and a shift of its peak to lower frequencies. On the other hand, increasing the confining pressure causes a reduction in the attenuation magnitude and a shift of its peak to higher frequencies. For saturation levels above ~98%, the fluid pressure increases with increasing confining pressure. When the fluid pressure is high enough to ensure full water saturation of the Sample, attenuation becomes negligible. A second series of comparable experiments reproduces these results satisfactorily. Based on a qualitative analysis of the data, the frequency-dependent attenuation meets the theoretical predictions of mesoscopic wave-induced fluid flow (WIFF) in response to a heterogeneous water distribution in the pore space, so-called patchy saturation. These results show that mesoscopic WIFF can be an important source of seismic attenuation at reservoir conditions.
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laboratory measurements of seismic wave attenuation in berea Sandstone as a function of water saturation and confining pressure
Seg Technical Program Expanded Abstracts, 2015Co-Authors: Samuel Chapman, Nicola Tisato, Beatriz Quintal, Klaus HolligerAbstract:We measure extensional-mode attenuation and dynamic Young’s modulus on a Berea Sandstone Sample at seismic frequencies (0.5-50 Hz). The results show a dependence of attenuation with frequency, water saturation and confining pressure. For water saturation levels above 80%, we observe a frequency-dependent bell-shaped attenuation curve with a peak between 1 and 20 Hz. For dry conditions, attenuation is very low and approximately frequencyindependent. Increasing the confining pressure on the Sample causes a reduction of the overall magnitude of the attenuation. The results indicate that the frequencydependent attenuation can be attributed to mesoscopic wave-induced fluid flow (WIFF) caused by heterogeneities in water saturation.
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measurements of seismic attenuation and transient fluid pressure in partially saturated berea Sandstone evidence of fluid flow on the mesoscopic scale
Geophysical Journal International, 2013Co-Authors: Nicola Tisato, Beatriz QuintalAbstract:S U M M A R Y A novel laboratory technique is proposed to investigate wave-induced fluid flow on the mesoscopic scale as a mechanism for seismic attenuation in partially saturated rocks. This technique combines measurements of seismic attenuation in the frequency range from 1 to 100 Hz with measurements of transient fluid pressure as a response of a step stress applied on top of the Sample. We used a Berea Sandstone Sample partially saturated with water. The laboratory results suggest that wave-induced fluid flow on the mesoscopic scale is dominant in partially saturated Samples. A 3-D numerical model representing the Sample was used to verify the experimental results. Biot’s equations of consolidation were solved with the finite-element method. Wave-induced fluid flow on the mesoscopic scale was the only attenuation mechanism accounted for in the numerical solution. The numerically calculated transient fluid pressure reproduced the laboratory data. Moreover, the numerically calculated attenuation, superposed to the frequency-independent matrix anelasticity, reproduced the attenuation measured in the laboratory in the partially saturated Sample. This experimental—numerical fit demonstrates that wave-induced fluid flow on the mesoscopic scale and matrix anelasticity are the dominant mechanisms for seismic attenuation in partially saturated Berea Sandstone.
Klaus Holliger - One of the best experts on this subject based on the ideXlab platform.
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seismic attenuation in partially saturated berea Sandstone submitted to a range of confining pressures
Journal of Geophysical Research, 2016Co-Authors: Samuel Chapman, Nicola Tisato, Beatriz Quintal, Klaus HolligerAbstract:Using the forced oscillation method, we measure the extensional-mode attenuation and Young's modulus of a Berea Sandstone Sample at seismic frequencies (0.5–50 Hz) for varying levels of water saturation (~0–100%) and confining pressures (2–25 MPa). Attenuation is negligible for dry conditions and saturation levels <80%. For saturation levels between ~91% and ~100%, attenuation is significant and frequency dependent in the form of distinct bell-shaped curves having their maxima between 1 and 20 Hz. Increasing saturation causes an increase of the overall attenuation magnitude and a shift of its peak to lower frequencies. On the other hand, increasing the confining pressure causes a reduction in the attenuation magnitude and a shift of its peak to higher frequencies. For saturation levels above ~98%, the fluid pressure increases with increasing confining pressure. When the fluid pressure is high enough to ensure full water saturation of the Sample, attenuation becomes negligible. A second series of comparable experiments reproduces these results satisfactorily. Based on a qualitative analysis of the data, the frequency-dependent attenuation meets the theoretical predictions of mesoscopic wave-induced fluid flow (WIFF) in response to a heterogeneous water distribution in the pore space, so-called patchy saturation. These results show that mesoscopic WIFF can be an important source of seismic attenuation at reservoir conditions.
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laboratory measurements of seismic wave attenuation in berea Sandstone as a function of water saturation and confining pressure
Seg Technical Program Expanded Abstracts, 2015Co-Authors: Samuel Chapman, Nicola Tisato, Beatriz Quintal, Klaus HolligerAbstract:We measure extensional-mode attenuation and dynamic Young’s modulus on a Berea Sandstone Sample at seismic frequencies (0.5-50 Hz). The results show a dependence of attenuation with frequency, water saturation and confining pressure. For water saturation levels above 80%, we observe a frequency-dependent bell-shaped attenuation curve with a peak between 1 and 20 Hz. For dry conditions, attenuation is very low and approximately frequencyindependent. Increasing the confining pressure on the Sample causes a reduction of the overall magnitude of the attenuation. The results indicate that the frequencydependent attenuation can be attributed to mesoscopic wave-induced fluid flow (WIFF) caused by heterogeneities in water saturation.
Mohammed Halawani - One of the best experts on this subject based on the ideXlab platform.
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Sandstone Sample analysis and additional structural data from jabal rayah a possible impact structure in saudi arabia
Meteoritics & Planetary Science, 2018Co-Authors: Edwin Gnos, Beda A Hofmann, Khalid Alwagdani, Ayman Mahjub, Abdulaziz A Alsolami, Siddiq N Habibullah, Albert Matter, Mohammed HalawaniAbstract:The ~ 5.5 km sized Jabal Rayah ring structure located at 28° 390 N/37° 120 E in Saudi-Arabia has been classified as a possible complex impact structure located in flat-lying-Paleozoic clastic sediments. Previous, detailed mapping showed that erosional processes led-to a relief inversion, with displaced, folded, and faulted blocks of Silurian to Early-Devonian strata, interpreted to form a ring syncline, now forming a topographically-outstanding, 150 m high ring crest. The drainage toward the center of the structure seems-controlled by a set of radial faults. This central part is eroded to the level of the-surrounding plateau and partially covered with gravel. Analysis of 28 Qusaiba Formation-Sandstones showed that at the present outcrop level, the sediments seem devoid of shock-features. Measurement of fold axes in the central part of the structure shows radially-outward plunging fold axes, becoming steeper toward the center, and also fold axes of other-orientation, and folded folds. This fold axis pattern is interpreted as an upward-pointing,-kilometer-sized sheath fold. Assuming an impact scenario and using the present size of the-structure, the minimum central structural uplift is estimated at ~ 500 m, which is consistent-with Qusaiba Formation occupying the center of the ring structure.
Alexandre Puyguiraud - One of the best experts on this subject based on the ideXlab platform.
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Upscaling of Anomalous Pore-Scale Dispersion
Transport in Porous Media, 2019Co-Authors: Alexandre Puyguiraud, Philippe Gouze, Marco DentzAbstract:We study the upscaling of advective pore-scale dispersion in terms of the Eulerian velocity distribution and advective tortuosity, both flow attributes, and of the average pore length, a medium attribute. The stochastic particle motion is modeled as a time-domain random walk, in which particles move along streamlines in equidistant spatial steps with random velocities and thus random transition times. Particle velocities describe stationary spatial Markov processes, which evolve along streamlines on the mean pore length. The streamwise motion is projected onto the mean flow direction using tortuosity. This upscaled stochastic particle model predicts accurately the (non-Fickian) transport dynamics obtained from direct numerical simulations of particle transport in a three-dimensional digitized Berea Sandstone Sample. It captures all aspects of transport and sheds light on the dependence of the upscaled transport behavior on the flow heterogeneity and the initial particle distribution, which are critical for the accurate modeling of dispersion from the pre-asymptotic to asymptotic regimes.
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Changement d'échelle du transport hydrodynamique en méchelle : du pore à l'échelle de Darcy en utilisantla méthode Continuous Time Random Walk
2019Co-Authors: Alexandre PuyguiraudAbstract:The mechanisms responsible for anomalous (non-Fickian) hydrodynamictransport can be traced back to the complexity of the medium geometry atthe pore-scale. In this thesis, we investigate the dynamics of pore-scaleparticle velocities. Using particle tracking simulations performed on adigitized Berea Sandstone Sample, we present a detailed analysis of theevolution of the Lagrangian and Eulerian evolution and their dependenceon the initial conditions. The particles experience a complexintermittent temporal velocity signal along their streamline while theirspatial velocity series exhibit regular fluctuations. The spatialvelocity distribution of the particles converges quickly to thesteady-state. These results lead naturally to Markov processes for theprediction of these velocity series.These processes, together with the tortuosity and the velocitycorrelation distance that are properties of the medium, allow theparameterization of a continuous time random walk (CTRW) for theupscaling of the transport. The model, like any upscaled model, relieson the definition of a representative elementary volume (REV). We showthat an REV based on the velocity statistics allows defining a pertinentsupport for modeling pre-asymptotic to asymptotic hydrodynamictransport at Darcy scale using, for instance, CTRW, thus overcomingthe limitations associated with the Fickian advection dispersionequation. Finally, we investigate the impact of pore-scale heterogeneityon a bimolecular reaction and explore a methodology for the predictionof the mixing volume and the chemical mass produced.
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Stochastic Dynamics of Lagrangian Pore‐Scale Velocities in Three‐Dimensional Porous Media
Water Resources Research, 2019Co-Authors: Alexandre Puyguiraud, Philippe Gouze, Marco DentzAbstract:Upscaling dispersion, mixing, and reaction processes from the pore to the Darcy scale is directly related to the understanding of the dynamics of pore-scale particle velocities, which are at the origin of hydrodynamic dispersion and non-Fickian transport behaviors. With the aim of deriving a framework for the systematic upscaling of these processes from the pore to the Darcy scale, we present a detailed analysis of the evolution of Lagrangian and Eulerian statistics and their dependence on the injection condition. The study is based on velocity data obtained from computational fluid dynamics simulations of Stokes flow and advective particle tracking in the three-dimensional pore structure obtained from high-resolution X-ray microtomography of a Berea Sandstone Sample. While isochronously Sampled velocity series show intermittent behavior, equidistant series vary in a regular random pattern. Both statistics evolve toward stationary states, which are related to the Eulerian velocity statistics. The equidistantly Sampled Lagrangian velocity distribution converges on only a few pore lengths. These findings indicate that the equidistant velocity series can be represented by an ergodic Markov process. A stochastic Markov model for the equidistant velocity magnitude captures the evolution of the Lagrangian velocity statistics. The model is parameterized by the Eulerian velocity distribution and a relaxation length scale, which can be related to hydraulic properties and the medium geometry. These findings lay the basis for a predictive stochastic approach to upscale solute dispersion in complex porous media from the pore to the Darcy scale.
