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Martin J. Blunt - One of the best experts on this subject based on the ideXlab platform.

  • Pore-Scale Modeling: Effects of wettability on waterflood oil recovery
    Journal of Petroleum Science and Engineering, 2010
    Co-Authors: Xiucai Zhao, Martin J. Blunt
    Abstract:

    We study the effects of wettability on waterflood oil recovery using a capillary-controlled Pore-Scale network model. We validate the model against experimental data in the literature on mixed-wet Berea sandstone and then apply it to study multiphase flow through four networks extracted from different types of rock: a sand pack, a poorly consolidated sandstone from the Middle East, a granular carbonate and Berea sandstone. We study the effects of initial water saturation, contact angle distribution and oil-wet fraction on recovery. For a uniformly-wet system, where the contact angle everywhere falls within a relatively narrow range, recovery increases as the system becomes less water-wet and reaches a maximum for oil-wet conditions where recovery is approximately constant for average intrinsic contact angles above 100°. As the initial water saturation increases, recovery decreases in water-wet systems whereas in oil-wet systems it initially increases and then decreases. For mixed-wet systems that contain water-wet and oil-wet regions of the pore space, the oil-wet fraction plays a more important role in determining recovery than the contact angle in the oil-wet regions. Optimal recovery occurs when a small fraction of the system is water-wet. Pore structure plays a relatively minor role in the generic behavior, although it does influence the initial saturation for maximum recovery and the magnitude of the recovery. These results are explained in terms of Pore-Scale displacement mechanisms and fluid configurations.

  • Predictive Pore Scale Modeling: From 3D Images to Multiphase Flow Simulations
    All Days, 2008
    Co-Authors: Olumide Talabi, Martin J. Blunt, Saif Alsayari, Hu Dong, Xiucai Zhao
    Abstract:

    Abstract We demonstrate and validate predictive Pore-Scale Modeling: we start with three-dimensional images of small rock samples obtained using micro-CT scanning with a resolution of a few microns, extract networks from these images and then predict multiphase flow properties by simulating capillary-controlled displacement. We study two sand packs, a poorly consolidated sandstone, Berea sandstone and a carbonate. Single-phase flow properties can be computed on a binarized image directly: we calculate the absolute permeability, resistivity and NMR response. We also extract topologically equivalent networks of pores and throats using a maximal ball method. As a quality control we compare single-phase predictions on these networks with those obtained on the images and from experiment: the permeability and NMR response are similar although we tend to underestimate the resistivity. Networks representing consolidated media tend to over-estimate the magnetization decay in an NMR experiment. We then compute multiphase properties, including capillary pressure, relative permeability and NMR response as a function of wettability (the contact angle distribution assigned to pores and throats). Experimental data, where available, is used to validate our predictions; where we know the wettability and pore structure, we are able to predict multiphase flow properties accurately. We show how relative permeability and capillary pressure is affected by rock type - principally the coordination number of the pores and the pore size distribution - and wettability. We suggest that predictive Pore-Scale Modeling combined with micro-CT imaging is a useful tool, complementary to special core analysis, for the determination of single and multiphase flow properties. Introduction Three-dimensional (3D) images of rock microstructure are the basis for the prediction of rock flow properties. These images are commonly generated using X-ray computed tomography (Hazlet, 1995; Arns et al., 2004), stochastic microstructural Modeling, (Adler et al., 1990; Liang et al., 1998; Okabe and Blunt, 2004) or process-based simulation of rock forming processes (Bryant et al., 1993, Bakke and Øren, 1997; Øren and Bakke, 2003; Jin et al., 2003). These images are then used to compute macroscopic flow properties by solving numerically the continuum flow equations governing fluid transport. Several single-phase properties such as permeability, electrical resistivity and NMR response have been predicted from 3D images (Øren et al., 2002; Arns et al., 2004; Knackstedt et al., 2004, Sakellariou et al., 2007) and these have been shown to be in goodagreement with conventional laboratory measurements (Arns et. al., 2001; 2002 and 2004). An alternative approach to the prediction of transport properties directly on 3D images is the use of Pore-Scale network models (Fatt, 1956; Chatzis and Dullien, 1977; Bryant et al., 1993; Blunt et al., 2002). To make accurate predictions they should be derived from 3D images (Lindquist et al., 1996; Bakke and Øren, 1997; Delerue et al., 2002) so as to make them topologically similar to the original samples. Capillary pressure, relative permeability and formation factor have been predicted from network models and have been shown to be in good agreement with experimental data (Bakke and Øren, 1997; Øren and Bakke, 2003, Valvatne and Blunt, 2004, Piri and Blunt 2005b).

  • Pore-Scale Modeling of Rate Effects in Waterflooding
    Proceedings of International Petroleum Technology Conference, 2008
    Co-Authors: Nasiru Idowu, Martin J. Blunt
    Abstract:

    We develop a rate-dependent network model that accounts for viscous forces by solving for the wetting and non-wetting phase pressure and which allows wetting layer swelling near an advancing flood front. The model incorporates a new time-dependent algorithm by accounting for partial filling of elements. We use the model to study the effects of capillary number, mobility ratio and contact angle distribution on waterflood displacement patterns, saturation and velocity profiles. By using large networks, generated from a new stochastic network algorithm, we reproduce Buckley–Leverett profiles directly from Pore-Scale modelling thereby providing a bridge between Pore-Scale and macro-scale transport.

  • Predictive Pore-Scale Modeling of Single and Multiphase Flow
    Transport in Porous Media, 2005
    Co-Authors: Perh H. Valvatne, Mohammad Piri, Xavier Lopez, Martin J. Blunt
    Abstract:

    We show how to predict flow properties for a variety of rocks using Pore-Scale Modeling with geologically realistic networks. The pore space is represented by a topologically disordered lattice of pores connected by throats that have angular cross-sections. We successfully predict single-phase non-Newtonian rheology, and two and three-phase relative permeability for water-wet media. The pore size distribution of the network can be tuned to match capillary pressure data when a network representation of the system of interest is unavailable. The aim of this work is not simply to match experiments, but to use easily acquired data to estimate difficult to measure properties and to predict trends in data for different rock types or displacement sequences.

  • Predicting the Impact of Non-Newtonian Rheology on Relative Permeability Using Pore-Scale Modeling
    All Days, 2004
    Co-Authors: Xavier Lopez, Martin J. Blunt
    Abstract:

    Abstract Polymers are frequently used in waterflooding to ensure stable displacement and to control excessive water production. The viscosity of the polymer is a function of shear rate. Typically they are shear-thinning fluids whose apparent viscosity in a porous medium decreases with increasing flow rate. We use Pore-Scale network Modeling to predict the single- and multi-phase properties of shear thinning fluids in porous media. The model uses networks that represent the disordered topology of real rocks. For single-phase flow we can accurately predict experimentally measured relationships between apparent viscosity and flow rate. We simulate two-phase primary drainage and secondary imbibition in a water-wet system, where the wetting phase (polymer in aqueous solution) is non-Newtonian (shear-thinning) while the non-wetting phase (oil) remains Newtonian. We can predict the relative permeabilities for Newtonian fluids in Berea sandstone accurately. We then use the Pore-Scale model to predict trends in relative permeability as a function of flow rate in Berea sandstone for a non-Newtonian wetting phase. The relative permeability is defined as the ratio of the flow rate in multi-phase flow to the corresponding flow rate in single-phase flow with the same pressure gradient with the same shear-thinning fluid. The non-Newtonian phase relative permeability initially decreases with increasing pressure gradient before increasing again, while always remaining below the Newtonian values. This effect is most pronounced at low wetting phase saturation. When the wetting phase is confined to layers in the pore space, the shear rate is less than that experienced in single-phase flow when the pore is completely filled with fluid. This leads to higher effective viscosities and an apparent decrease in relative permeability. Introduction There are many aspects of hydrocarbon production processes where understanding the flow of non-Newtonian fluids in porous media is of great interest. These include well drilling and construction, reservoir stimulation and production1. In particular, complex polymeric solutions have been used for water-control purposes or to enhance oil recovery during secondary water flooding of reservoirs. Because of high viscosity and enhanced stability, these polymer-thickened solutions can act as effective mobility control during improved oil recovery applications2,3. For reservoir engineering purposes, one must have a prior knowledge of the macroscopic behavior, i.e. flow and transport properties, of such solutions in order to optimize any field application. Although there are other types of polymer used in the oil industry for hydrocarbon recovery, we will focus on the flow of Xanthan gum solutions in porous media that occurs in improved oil recovery processes. Xanthan biopolymer solutions are pseudo-plastic (shear-thinning) and show negligible elastic effects4. Assessing the efficiency of displacing oil by Xanthan polymer will normally require running field-scale reservoir simulations. However, the appropriate bulk and in-situ macroscopic behaviors of the polymeric solution must be given as input to the simulation model. We use Pore-Scale Modeling to describe and quantify the displacement mechanisms of Xanthan solutions in porous media. The approach uses networks based on real rocks that capture their complex geometry and topology as input to our flow model. By applying the right physics at the Pore-Scale, one can describe the macroscopic flow properties of polymer flooding and subsequently use these results to design field applications. Network Modeling In network Modeling, the void space of a rock is represented at the microscopic scale by a lattice of pores connected by throats. Macroscopic properties, such as capillary pressure or relative permeability, can be estimated across the network by applying the appropriate rules that govern the transport and arrangement of fluids at the Pore-Scale5–7.

Wen-quan Tao - One of the best experts on this subject based on the ideXlab platform.

  • Thermal conductivity of composite building materials: A pore scale Modeling approach
    International Journal of Heat and Mass Transfer, 2020
    Co-Authors: Mazhar Hussain, Wen-quan Tao
    Abstract:

    Abstract In this article the effective thermal conductivity (ETC) of a wide range of multiphase porous building materials has been estimated numerically. The numerical random generation macro-meso pores (RGMMP) method, which is based on the macroscopic statistical information, such as the porosity, volume fraction of macro-meso pores, is used here for the reconstruction of microstructures of various porous building materials. The distribution of macro-meso pores and their sizes are controlled by core distribution probability and porosity. The lattice Boltzmann method equipped with the conservation of energy and suitable boundary conditions at multiple interfaces is adopted for the numerical solution of energy transport equations through the porous media. After comparison with the benchmark of some theoretical solutions and existing experimental observations, it is employed for the estimation of ETC of different multiphase building materials. The resultant predictions through proposed model accord much better with the existing experimental data than the values obtained through traditional theoretical models. Moreover, comparison of the current reconstruction method, RGMMP, with previously proposed Quartet Structure Generation Set (QSGS) method indicated that predictions with present model is more accurate than those obtained with QSGS. Finally the method is applied for analyzing the variation of ETC with temperature and found that value of thermal conductivity rises with increase in temperature for all the mentioned building materials.

  • pore scale Modeling of multiphase reactive transport with phase transitions and dissolution precipitation processes in closed systems
    Physical Review E, 2013
    Co-Authors: Qinjun Kang, Li Chen, Bruce A Robinson, Wen-quan Tao
    Abstract:

    A Pore-Scale model based on the lattice Boltzmann (LB) method is developed for multiphase reactive transport with phase transitions and dissolution-precipitation processes. The model combines the single-component multiphase Shan-Chen LB model [X. Shan and H. Chen, Phys. Rev. E 47, 1815 (1993)], the mass transport LB model [S. P. Sullivan et al., Chem. Eng. Sci. 60, 3405 (2005)], and the dissolution-precipitation model [Q. Kang et al., J. Geophys. Res. 111, B05203 (2006)]. Care is taken to handle information on computational nodes undergoing solid-liquid or liquid-vapor phase changes to guarantee mass and momentum conservation. A general LB concentration boundary condition is proposed that can handle various concentration boundaries including reactive and moving boundaries with complex geometries. The Pore-Scale model can capture coupled nonlinear multiple physicochemical processes including multiphase flow with phase separations, mass transport, chemical reactions, dissolution-precipitation processes, and dynamic evolution of the pore geometries. The model is validated using several multiphase flow and reactive transport problems and then used to study the thermal migration of a brine inclusion in a salt crystal. Multiphase reactive transport phenomena with phase transitions between liquid-vapor phases and dissolution-precipitation processes of the salt in the closed inclusion are simulated and the effects of the initial inclusion size and temperature gradient on the thermal migration are investigated.

Moran Wang - One of the best experts on this subject based on the ideXlab platform.

  • Pore-Scale Modeling of chloride ion diffusion in cement microstructures
    Cement and Concrete Composites, 2018
    Co-Authors: Yuankai Yang, Moran Wang
    Abstract:

    Abstract Understanding the mechanism of chloride ion diffusion in cement is significant to improve the reliability of offshore reinforced concrete structures. The chloride ionic diffusivity in cement-based microstructures is predicted by Pore-Scale Modeling using a modified lattice Boltzmann method. Both the Nernst-Planck equation for ion diffusion and the Poisson equation for electrodynamic effect are fully solved. The predicted effective diffusivities in cement-based microstructures with different porosities are in good agreements with the experiment data. The results show that the pore size distribution and Zeta potential of cement-based microstructures directly influence the effective diffusivities of chloride ions. The cement-based microstructure with smaller pore size and higher negative Zeta potential hinders chloride ions corrosion more effectively. The electrokinetic effect on the chloride ionic transport is negligible when the ratio of the maximum-probability pore size and the Debye length is higher than 32 in the cement-based microstructure. For engineering applications, we provide a predictive and easy-to-use formula by up-scaling to correlate the effective chloride ion diffusivity with electrokinetic effect in cement paste.

  • Bonding Strength Effects in Hydro-Mechanical Coupling Transport in Granular Porous Media by Pore-Scale Modeling
    Computation, 2016
    Co-Authors: Zhiqiang Chen, Chiyu Xie, Yu Chen, Moran Wang
    Abstract:

    The hydro-mechanical coupling transport process of sand production is numerically investigated with special attention paid to the bonding effect between sand grains. By coupling the lattice Boltzmann method (LBM) and the discrete element method (DEM), we are able to capture particles movements and fluid flows simultaneously. In order to account for the bonding effects on sand production, a contact bond model is introduced into the LBM-DEM framework. Our simulations first examine the experimental observation of “initial sand production is evoked by localized failure” and then show that the bonding or cement plays an important role in sand production. Lower bonding strength will lead to more sand production than higher bonding strength. It is also found that the influence of flow rate on sand production depends on the bonding strength in cemented granular media, and for low bonding strength sample, the higher the flow rate is, the more severe the erosion found in localized failure zone becomes

  • Permeability of high-Kn real gas flow in shale and production prediction by Pore-Scale Modeling
    Journal of Natural Gas Science and Engineering, 2016
    Co-Authors: Ziyan Wang, Yangyu Guo, Moran Wang
    Abstract:

    Abstract Although shale gas has been commercially exploited, the gas transport mechanism in shale is still unclear. Because nanoscale pores are dominant in shale, the Knudsen number of the flow is relatively high so that the conventional Darcy's law fails. What is more, the shale gas in situ is under high pressure and high temperature so that the real gas (or non-ideal gas) effect is significant. Aiming at these two challenges, we did a Pore-Scale Modeling by using lattice Boltzmann method in this work. We developed a pore-field-iteration (PFI) method to bridge up the Pore-Scale Modeling results with the field-scale concerns, such as inflow performance relationship and decline curve analysis. Our results show that the high Knudsen effect leads to a higher gas flow rate, while the real gas effect causes lower gas flow rate. The gas production may be overestimated at early stage due to the real gas effect, while underestimated at late stage because of the high Knudsen number effect. These results may be very helpful for better understanding of gas transport mechanism in shale and for possible process optimization of shale gas developments in future.

Cho Lik Chan - One of the best experts on this subject based on the ideXlab platform.

David M Loveless - One of the best experts on this subject based on the ideXlab platform.

  • nanometer scale characterization of microscopic pores in shale kerogen by image analysis and pore scale Modeling
    Geochemistry Geophysics Geosystems, 2013
    Co-Authors: Cheng Chen, Donald Westacott, David M Loveless
    Abstract:

    [1] Nanometer-scale scanning electron microscopy was applied in visualizing the microscopic pores within shale kerogen. Geometrical information of all individual pores was extracted by image analysis. Image segmentation and separation showed that most of the intrakerogen pores are discrete and isolated from each other, having relatively spherical morphology. These isolated intrakerogen pores result in huge challenges in gas production, because they are not effectively connected to natural and hydraulic fractures. Statistical results showed that nanopores, which have diameters smaller than 100 nm, make up 92.7% of the total pore number, while they make up only 4.5% of the total pore volume. Intrakerogen porosity and specific surface area are 29.9% and 14.0 m2/g, respectively. Accurate visualization and measurement of intrakerogen pores are critical for evaluation of gas storage and optimization of hydraulic fracturing. By lattice Boltzmann simulations, permeabilities and tortuosities were simulated in the three principal directions. Long tails were observed in breakthrough curves, resulting from diffusion of solute particles from low-flow-velocity pores to larger conduits at late times. The long-tailing phenomena at the pore scale are qualitatively consistent with those observed in real productions. Understanding the Pore-Scale transport processes between microscopic pores within kerogen and large fracture systems is of great importance in predicting hydrocarbon production. Upscaling methods are needed to investigate larger-scale processes and properties in shale reservoirs.