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  • 1
    Electronic Resource
    Electronic Resource
    Nested gridding and streamline-based simulation for fast reservoir performance prediction (1999)
    Springer
    Computational geosciences 3 (1999), S. 295-320 
    Details
    ISSN: 1573-1499
    Keywords: upscaling ; multiphase flow simulation ; streamline methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Computer Science
    Notes: Abstract Detailed reservoir models routinely contain 106–108 grid blocks. These models often cannot be used directly in a reservoir simulation because of the time and memory required for solving the pressure grid on the fine grid. We propose a nested gridding technique that efficiently obtains an approximate solution for the pressure field. The domain is divided into a series of coarse blocks, each containing several fine cells. Effective mobilities are computed for each coarse grid block and the pressure is then found on the coarse scale. The pressure field within each coarse block is computed using flux boundary conditions obtained from the coarse pressure solution. Streamline-based simulation is used to move saturations forward in time. We test the method for a series of example waterflood problems and demonstrate that the method can give accurate estimates of oil production for large 3D models significantly faster than direct simulation using streamlines on the fine grid, making the method overall approximately up to 1,000 times faster than direct conventional simulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011535210857
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  • 2
    Electronic Resource
    Electronic Resource
    Pore Scale Modeling of Rate Effects in Imbibition (2000)
    Springer
    Transport in porous media 40 (2000), S. 295-322 
    Details
    ISSN: 1573-1634
    Keywords: network modeling ; relative permeability ; imbibition ; pore scale ; multiphase flow in porous media ; fractures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract We use pore scale network modeling to study the effects of flow rate and contact angle on imbibition relative permeabilities. The model accounts for flow in wetting layers that occupy roughness or crevices in the pore space. Viscous forces are accounted for by solving for the wetting phase pressure and assuming a fixed conductance in wetting layers. Three-dimensional simulations model granular media, whereas two-dimensional runs represent fracture flow. We identify five generic types of displacement pattern as we vary capillary number, contact angle, and initial wetting phase saturation: flat frontal advance, dendritic frontal advance, bond percolation, compact cluster growth, and ramified cluster growth. Using phase diagrams we quantify the range of physical properties under which each regime is observed. The work explains apparently inconsistent experimental measurements of relative permeability in granular media and fractures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006629019153
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  • 3
    Electronic Resource
    Electronic Resource
    Micromodel Observation of the Role of Oil Layers in Three-Phase Flow (1997)
    Springer
    Transport in porous media 26 (1997), S. 277-297 
    Details
    ISSN: 1573-1634
    Keywords: NAPL ; multiphase flow ; three-phase flow ; film flow ; micromodel ; spreading coefficient ; non-spreading oil.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract We have studied the flow of a non-aqueous phase liquid (NAPL, or oil), water and air at the pore scale using a micromodel. The pore space pattern from a photomicrograph of a two-dimensional section through a Berea sandstone was etched onto a silicon wafer. The sizes of the pores in the micromodel are in the range 3–30,μm and are the same as observed in the rock from which the image was taken. We conducted three-phase displacement experiments at low capillary numbers (in the order of 10-7) to observe the presence of predicted displacement mechanisms at the pore scale. We observed stable oil layers between the wetting phase (water) and the non-wetting phase (gas) for the water–decane–air system, which has a negative equilibrium spreading coefficient, as well as four different types of double displacements where one fluid displaces another that displaces a third. Double imbibition and double drainage are readily observed, but the existence of an oil layer surrounding the gas phase makes the other double displacement combinations very unlikely.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006589611884
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  • 4
    Electronic Resource
    Electronic Resource
    Behavior of Nonaqueous Phase Liquids in Fractured Porous Media under Two‐Phase Flow Conditions (2000)
    Springer
    Transport in porous media 38 (2000), S. 189-203 
    Details
    ISSN: 1573-1634
    Keywords: NAPL ; capillary pressure ; relative permeability ; network model ; multiphase flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract After dense nonaqueous phase liquids (DNAPLs) travel downward through the subsurface, they typically come to rest on fractured bedrock or tight clay layers, which become additional pathways for DNAPL migration. DNAPLs trapped in fractures are continuous sources of groundwater contamination. To decide whether they can be left in place to dissolve or volatilize, or must be removed with active treatment, the movement of DNAPLs in fractured media must be understood at a fundamental level. This work presents numerical simulations of the movements of DNAPLs in naturally fractured media under two‐phase flow conditions. The flow is modeled using a multiphase network flow model, used to develop predictive capabilities for DNAPL flow in fractures. Capillary pressure–saturation–relative permeability curves are developed for two‐phase flow in fractures. Comparisons are made between the behavior in crystalline, almost impermeable rocks (e.g. granite) and more permeable rocks like sandstone, to understand the effects of the rock matrix on the displacement of the DNAPLs in the fracture. For capillary‐dominated flow, displacements occur as a sequence of jumps, as the invading phase overcomes the capillary pressure at downgradient apertures. Preferential channels for the displacement of nonaqueous phase are formed due to high fracture aperture in some regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006619402305
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  • 5
    Electronic Resource
    Electronic Resource
    A Physically Based Model of Dissolution of Nonaqueous Phase Liquids in the Saturated Zone (2000)
    Springer
    Transport in porous media 39 (2000), S. 227-255 
    Details
    ISSN: 1573-1634
    Keywords: corner diffusion ; pore diffusion ; mixing and multiple contact ; bundle of parallel pores in series ; blob ; ganglia ; dissolution rate coefficient ; dissolution ; NAPL
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The design of remediation strategies for nonaqueous phase liquid (NAPL) contaminants involves predicting the rate of NAPL dissolution. A physically based model of an idealized pore geometry was developed to predict nonaqueous phase liquid dissolution rate coefficients. A bundle of parallel pores in series model is used to represent NAPL dissolution as a function of three processes: pore diffusion, corner diffusion, and mixing and multiple contact. The dissolution rate coefficient is expressed in terms of the modified Sherwood number (Sh′) and is a function of Peclet (Pe) number. The model captures the complex behavior of Sh′ versus Pe data for both water-wet (Powers, 1992) and NAPL-wet (Parker et al., 1991) media. For water-wet media, the observed behavior can be broken down into four distinct regions. Each region represents a different physical process controlling NAPL dissolution: the low-Pe region is controlled by pore diffusion; the low- to moderate-Pe region is a transition zone; the moderate-Pe region is controlled by mixing and multiple contact; and the high-Pe region is controlled by corner diffusion. For the high-Pe conditions typical of most column experiments, the model involves only one fitting parameter. For NAPL-wet media, NAPL dissolution is governed exclusively by corner diffusion, and the model again involves only one fitting parameter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006693126316
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  • 6
    Electronic Resource
    Electronic Resource
    The Effect of Wettability on Three-Phase Relative Permeability (2000)
    Springer
    Transport in porous media 39 (2000), S. 347-366 
    Details
    ISSN: 1573-1634
    Keywords: wettability ; relative permeability ; multiphase flow ; CT scanning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract We study three-phase flow in water-wet, oil-wet, and fractionally-wet sandpacks. We use CT scanning to measure directly the oil and water relative permeabilites for three-phase gravity drainage. In an analogue experiment, we measure pressure gradients in the gas phase to determine the gas relative permeability. Thus we find all three relative permeabilities as a function of saturation. We find that the gas relative permeability is approximately half as much in a oil-wet medium than in an water-wet medium at the same gas saturation. The water relative permeability in the water-wet medium and the oil relative permeability in the oil-wet medium are similar. In the water-wet medium the oil relative permeability scales as k ro ∼ S o 4 for S o 〉 S or, where S or is the waterflood residual oil saturation. With octane as the oil phase, k ro ∼ S o 2 for S o 〈 S or, while with decane as the oil phase, k ro falls sharply for S o 〈 S or. The water relative permeability in the oil-wet medium resembles the oil relative permeability in the water-wet medium for a non-spreading oil such as decane. These observations can be explained in terms of wetting, spreading, and the pore scale configurations of fluid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006653323374
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  • 7
    Electronic Resource
    Electronic Resource
    Quantifying uncertainty in reservoir performance using streamtubes (1996)
    Springer
    Mathematical geology 28 (1996), S. 843-856 
    Details
    ISSN: 1573-8868
    Keywords: reservoir simulation ; production forecasting ; streamtubes ; streamlines ; stochastic generation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract We present the use of a streamtube approach to study the uncertainty in reservoir performance resulting from a stochastic description of the flow domain. The streamtube technique is an efficient numerical method which is particularly effective for modeling convective displacements that are dominated by large-scale heterogeneities. Stable, numerical-diffusion-free solutions can be obtained in a fraction of the time taken by conventional finite difference simulators, thereby allowing a statistical approach to reservoir simulation and forecasting.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02066004
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  • 8
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    Dynamic fluid connectivity during steady-state multiphase flow in a sandstone (2017)
    National Academy of Sciences
    Details
    Publication Date: 2017-07-17
    Description: The current conceptual picture of steady-state multiphase Darcy flow in porous media is that the fluid phases organize into separate flow pathways with stable interfaces. Here we demonstrate a previously unobserved type of steady-state flow behavior, which we term “dynamic connectivity,” using fast pore-scale X-ray imaging. We image the flow of N2 and brine through a permeable sandstone at subsurface reservoir conditions, and low capillary numbers, and at constant fluid saturation. At any instant, the network of pores filled with the nonwetting phase is not necessarily connected. Flow occurs along pathways that periodically reconnect, like cars controlled by traffic lights. This behavior is consistent with an energy balance, where some of the energy of the injected fluids is sporadically converted to create new interfaces.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 9
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    Wettability in complex porous materials, the mixed-wet state, and its relationship to surface roughness (2018)
    National Academy of Sciences
    Details
    Publication Date: 2018-08-17
    Description: A quantitative in situ characterization of the impact of surface roughness on wettability in porous media is currently lacking. We use reservoir condition micrometer-resolution X-ray tomography combined with automated methods for the measurement of contact angle, interfacial curvature, and surface roughness to examine fluid/fluid and fluid/solid interfaces inside a porous material. We study oil and water in the pore space of limestone from a giant producing oilfield, acquiring millions of measurements of curvature and contact angle on three millimeter-sized samples. We identify a distinct wetting state with a broad distribution of contact angle at the submillimeter scale with a mix of water-wet and water-repellent regions. Importantly, this state allows both fluid phases to flow simultaneously over a wide range of saturation. We establish that, in media that are largely water wet, the interfacial curvature does not depend on solid surface roughness, quantified as the local deviation from a plane. However, where there has been a significant wettability alteration, rougher surfaces are associated with lower contact angles and higher interfacial curvature. The variation of both contact angle and interfacial curvature increases with the local degree of roughness. We hypothesize that this mixed wettability may also be seen in biological systems to facilitate the simultaneous flow of water and gases; furthermore, wettability-altering agents could be used in both geological systems and material science to design a mixed-wetting state with optimal process performance.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 10
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    Signature of Non-Fickian Solute Transport in Complex Heterogeneous Porous Media (2011)
    American Physical Society
    Details
    Publication Date: 2011-11-08
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society
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