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H J Herrmann - One of the best experts on this subject based on the ideXlab platform.
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granular front formation in free surface flow of concentrated suspensions
Physical Review E, 2015Co-Authors: Alessandro Leonardi, Roland Kaitna, Miguel Angel Cabrera, M. Mendoza, Falk K. Wittel, Wei Wu, H J HerrmannAbstract:A granular front emerges whenever the free-surface flow of a concentrated suspension spontaneously alters its internal structure, exhibiting a higher concentration of particles close to its front. This is a common and yet unexplained phenomenon, which is usually believed to be the result of fluid convection in combination with particle size segregation. However, suspensions composed of uniformly sized particles also develop a granular front. Within a large rotating drum, a stationary recirculating avalanche is generated. The Flowing Material is a mixture of a viscoplastic fluid obtained from a kaolin-water dispersion with spherical ceramic particles denser than the fluid. The goal is to mimic the composition of many common granular-fluid Materials, such as fresh concrete or debris flow. In these Materials, granular and fluid phases have the natural tendency to separate due to particle settling. However, through the shearing caused by the rotation of the drum, a reorganization of the phases is induced, leading to the formation of a granular front. By tuning the particle concentration and the drum velocity, it is possible to control this phenomenon. The setting is reproduced in a numerical environment, where the fluid is solved by a lattice-Boltzmann method, and the particles are explicitly represented using the discrete element method. The simulations confirm the findings of the experiments, and provide insight into the internal mechanisms. Comparing the time scale of particle settling with the one of particle recirculation, a nondimensional number is defined, and is found to be effective in predicting the formation of a granular front.
Olivier Roche - One of the best experts on this subject based on the ideXlab platform.
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impact of fluidized granular flows into water implications for tsunamis generated by pyroclastic flows
Journal of Geophysical Research, 2020Co-Authors: Alexis Bougouin, Raphael Paris, Olivier RocheAbstract:Novel laboratory experiments of fluidized granular flows entering water are reported, for the purpose of investigating tsunamis generated by pyroclastic flows. Qualitatively, the impact of a fluidized granular flow into water leads to (i) an initial vertical granular jet over water, (ii) a leading and largest wave, and (iii) a turbulent mixing zone forming a turbidity current. The present study focuses on the leading wave features in the near‐field region, as a function of the mass flux per width qm and the volume per width υ of the flow, the maximum water depth Ho, and the slope angle θ of the inclined plane. The obtained waves are of Stokes and cnoidal types, for which the generation is mostly controlled by qm and υ. By contrast, Ho plays no role on the wave generation that occurs in the shallowest region. Moreover, a comparison between fluidized granular, dry (nonfluidized) granular, and water flows entering water is addressed under similar flow conditions. The dimensionless amplitude scales as A/Ho=f(ζ), where urn:x-wiley:jgrb:media:jgrb54190:jgrb54190-math-0001 is a dimensionless parameter depending on the Froude number Fr, the relative slide thickness S, the relative mass M, and the slope angle θ. Data of fine fluidized granular, fine dry granular, and water flows collapse on a master curve, which implies that the nature of the Flowing Material is of lesser importance in the current setup. By contrast, coarse granular flows generate lower amplitude waves, which is attributed to the penetration of water into the porous granular medium.
Christopher R. Clarkson - One of the best experts on this subject based on the ideXlab platform.
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rate transient analysis of an undersaturated cbm reservoir in australia accounting for effective permeability changes above and below desorption pressure
Journal of Natural Gas Science and Engineering, 2017Co-Authors: Christopher R. Clarkson, Alireza SalmachiAbstract:Abstract Rate-transient analysis (RTA) of coalbed methane (CBM) wells is an on-going reservoir engineering challenge because of the dynamic nature of coal reservoirs. During their lifetime, producing CBM wells completed in initially undersaturated reservoirs (Flowing above desorption pressure) experience a change from single-phase water to two-phase (gas + water) production as desorption pressure is reached, and the production characteristics of these wells are affected by a multitude of dynamic CBM reservoir properties. Amongst the most important dynamic properties influencing production is absolute permeability of the natural fracture (cleat) network. Prolific coalbed methane wells in the Fairview Field, central Queensland, eastern Australia, exhibit stress-dependent permeability changes during early dewatering, followed by strong desorption-dependent permeability effects below desorption pressure. These effects, combined with the switch from single-phase to two-phase flow at desorption pressure, make quantitative production data analysis for reservoir properties (e.g. permeability and original gas-in-place) particularly challenging. In this study, a combination of Flowing Material balance (FMB) equations for gas and water, modified for dynamic changes in effective permeability, and analytical simulation is used to analyze a Fairview Field CBM well completed in coals of the Bandanna Formation using the cavitation technique. The subject well exhibits strong permeability changes for the first several years after desorption pressure is reached, after which permeability changes appear to occur more gradually. Single-phase water production data above desorption pressure is analyzed using an FMB method modified for stress-dependent permeability; gas production data below desorption pressure is analyzed using an FMB method modified to account for relative permeability and desorption-dependent permeability. Because of uncertainty in below-desorption pressure FMB model inputs, the FMB equations and analytical simulation are linked. This approach allows for a consistent, if not unique, analysis. The RTA approach outlined herein provides a reasonable starting point for more rigorous numerical simulation, which in turn can be used for reserves forecasting and development planning. Because of the multitude of reservoir properties (several of the key properties being dynamic) affecting the production characteristics of CBM wells such as those in the Fairview Field, it is important to advance RTA methods to constrain numerical model inputs.
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case study production data and pressure transient analysis of horseshoe canyon cbm wells
Journal of Canadian Petroleum Technology, 2009Co-Authors: Christopher R. ClarksonAbstract:The Horseshoe Canyon (HSC) CBM play of the Western Canadian Sedimentary Basin is unique to low-rank coal reservoirs because of lack of water production; the production characteristics are qualitatively similar to conventional low-pressure dry gas reservoirs. However, the complex geological history of the coals and non-coal interbeds has imparted strong vertical and lateral heterogeneities that make the play difficult to characterize using conventional methods. Recently, advances in production data analysis (PDA) methodologies have been made for CBM wells; techniques developed for conventional oil and gas reservoirs have been adapted by incorporating some CBM reservoir properties. For example, the popular Flowing Material balance (FMB) technique, as well as production type-curve and pressure transient analysis (PTA) have been modified to include relatively simple CBM reservoir behaviour (ex. equilibrium desorption). These methods, however, are primarily restricted to the analysis of single-layer reservoirs ; significant errors in estimates of original-gas-in-place (OGIP) and other reservoir properties may occur if strong contrasts exist from layer-to-layer. In this work, multi-layer analysis tools are discussed, including analytical simulators that are used to history-match layer-allocated rates and pressures, and layer-specific FMB, which is used as a PDA method for individual layers. The applicability of advanced PDA methods to the quantitative assessment of HSC reserves was investigated. Single-layer and multi-layer analysis tools were first tested against simulated data. Next, single-layer-equivalent analysis was performed on >40 real wells using type-curve, FMB, and analytical simulation. Finally, a more rigorous multi-layer analysis was performed on a subset of wells where spinner surveys and individual-seam pressure buildup data were available. Analysis of these wells included PTA of the individual seams, individual seam Material balance, and multi-layer analytical model history-matching of total commingled flow rates, individual coal zone rates estimated from spinner surveys and shut-in pressures. The single-layer-equivalent analysis appears to yield conservative estimates of OGIP compared to the more rigorous multi-layer analysis in the cases analyzed. Future work will include continued comparisons of multi-layer vs. single-layer PDA, investigation of additional constraints on input reservoir properties used in multi-layer history-matching process, and time-lapse PTA work to quantify changes in layer permeability and skin during depletion.
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Production-Data Analysis of Single-Phase (Gas) Coalbed-Methane Wells
Spe Reservoir Evaluation & Engineering, 2007Co-Authors: Christopher R. Clarkson, R. Marc Bustin, John P. SeidleAbstract:The current work illustrates how single-well production-data-analysis (PDA) techniques, such as type curve, Flowing Material balance (FMB), and pressure-transient (PT) analysis, may be altered to analyze single-phase CBM wells. Examples of how reservoir inputs to the PDA techniques and subsequent calculations are modified to account for CBM-reservoir behavior are given. This paper demonstrates, by simulated and field examples, that reasonable reservoir and stimulation estimates can be obtained from PDA of CBM reservoirs only if appropriate reservoir inputs (i.e., desorption compressibility, fracture porosity) are used in the analysis. As the field examples demonstrate, type-curve, FMB, and PT analysis methods for PDA are not used in isolation for reservoir-property estimation, but rather as a starting point for single-well and multiwell reservoir simulation, which is then used to history match and forecast CBM-well production (e.g., for reserves assignment). To study the effects of permeability anisotropy upon production, a 2D, single-phase, numerical CBM-reservoir simulator was constructed to simulate single-well production assuming various permeability-anisotropy ratios. Only large permeability ratios ({lt} 16:1) appear to have a significant effect upon single-well production characteristics. Multilayer reservoir characteristics may also be observed with CBM reservoirs because of vertical heterogeneity, or in cases where the coals are commingled with conventionalmore » (sandstone) reservoirs. In these cases, the type-curve, FMB, and PT analysis techniques are difficult to apply with confidence. Methods and tools for analyzing multilayer CBM (plus sand) reservoirs are presented. Using simulated and field examples, it is demonstrated that unique reservoir properties may be assigned to individual layers from commingled (multilayer) production in the simple two-layer case.« less
Alessandro Leonardi - One of the best experts on this subject based on the ideXlab platform.
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granular front formation in free surface flow of concentrated suspensions
Physical Review E, 2015Co-Authors: Alessandro Leonardi, Roland Kaitna, Miguel Angel Cabrera, M. Mendoza, Falk K. Wittel, Wei Wu, H J HerrmannAbstract:A granular front emerges whenever the free-surface flow of a concentrated suspension spontaneously alters its internal structure, exhibiting a higher concentration of particles close to its front. This is a common and yet unexplained phenomenon, which is usually believed to be the result of fluid convection in combination with particle size segregation. However, suspensions composed of uniformly sized particles also develop a granular front. Within a large rotating drum, a stationary recirculating avalanche is generated. The Flowing Material is a mixture of a viscoplastic fluid obtained from a kaolin-water dispersion with spherical ceramic particles denser than the fluid. The goal is to mimic the composition of many common granular-fluid Materials, such as fresh concrete or debris flow. In these Materials, granular and fluid phases have the natural tendency to separate due to particle settling. However, through the shearing caused by the rotation of the drum, a reorganization of the phases is induced, leading to the formation of a granular front. By tuning the particle concentration and the drum velocity, it is possible to control this phenomenon. The setting is reproduced in a numerical environment, where the fluid is solved by a lattice-Boltzmann method, and the particles are explicitly represented using the discrete element method. The simulations confirm the findings of the experiments, and provide insight into the internal mechanisms. Comparing the time scale of particle settling with the one of particle recirculation, a nondimensional number is defined, and is found to be effective in predicting the formation of a granular front.
Alexis Bougouin - One of the best experts on this subject based on the ideXlab platform.
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impact of fluidized granular flows into water implications for tsunamis generated by pyroclastic flows
Journal of Geophysical Research, 2020Co-Authors: Alexis Bougouin, Raphael Paris, Olivier RocheAbstract:Novel laboratory experiments of fluidized granular flows entering water are reported, for the purpose of investigating tsunamis generated by pyroclastic flows. Qualitatively, the impact of a fluidized granular flow into water leads to (i) an initial vertical granular jet over water, (ii) a leading and largest wave, and (iii) a turbulent mixing zone forming a turbidity current. The present study focuses on the leading wave features in the near‐field region, as a function of the mass flux per width qm and the volume per width υ of the flow, the maximum water depth Ho, and the slope angle θ of the inclined plane. The obtained waves are of Stokes and cnoidal types, for which the generation is mostly controlled by qm and υ. By contrast, Ho plays no role on the wave generation that occurs in the shallowest region. Moreover, a comparison between fluidized granular, dry (nonfluidized) granular, and water flows entering water is addressed under similar flow conditions. The dimensionless amplitude scales as A/Ho=f(ζ), where urn:x-wiley:jgrb:media:jgrb54190:jgrb54190-math-0001 is a dimensionless parameter depending on the Froude number Fr, the relative slide thickness S, the relative mass M, and the slope angle θ. Data of fine fluidized granular, fine dry granular, and water flows collapse on a master curve, which implies that the nature of the Flowing Material is of lesser importance in the current setup. By contrast, coarse granular flows generate lower amplitude waves, which is attributed to the penetration of water into the porous granular medium.