Imperial College London

Dr Qingyang Lin

Faculty of EngineeringDepartment of Earth Science & Engineering

Visiting Researcher
 
 
 
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Contact

 

+44 (0)20 7594 9982q.lin11 Website

 
 
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Location

 

RSM 440/7Royal School of MinesSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

73 results found

Pires LF, Ghanbarian B, Lin Q, 2024, Physical, topological and hydraulic properties of an Oxisol under conservation practices: X-ray tomography imaging and pore-network simulation, Soil and Tillage Research, Vol: 239, ISSN: 0167-1987

Pore structure plays an essential role in fluid flow and solute transport in soils. In this study, the physical, topological, and hydraulic properties of an Oxisol under two land uses, i.e., secondary forest (SF) and reduced tillage (RT), were characterized using a combination of X-ray computed tomography (XCT) imaging and pore network simulations. The SF was utilized as a baseline to assess changes in the pore structure of soils under the RT conditions. Tomographic images were obtained under three voxel sizes, i.e., 5.3, 35, and 60 μm. Porosity, surface area, Euler characteristic, and tortuosity were computed using image processing algorithms. The pore network of each soil sample was extracted to determine the pore-body radius, pore-throat radius, pore-throat length, and pore coordination number distributions as well as the absolute permeability. We found that the average pore-body radius, pore-throat radius, pore-throat length, and surface area increased with increasing voxel size for both land uses. No obvious differences in tortuosity and pore coordination number were observed between the 35 and 60 μm voxel sizes for both land uses but differ from those with 5.3 μm voxel size. Regarding pore connectivity, the images with 5.3 and 35 μm voxel sizes were similar, although they differed from the 60 μm images, whose samples were more connected. By analyzing the effect of land use, we found that, in general, there were little differences between the SF and RT at all voxel sizes examined. Exceptions occurred mainly for some of the physical properties determined on the images with the voxel size of 60 μm. The results of this study demonstrated the influence of different voxel sizes on the Oxisol properties. Despite the differences in image voxel sizes, distinctions between land uses were practically not found, which indicates that reduced tillage is an appropriate conservation system strategy to keep the soil physical structure quality.

Journal article

Qu ML, Yang J, Foroughi S, Zhang Y, Yu ZT, Blunt MJ, Lin Qet al., 2024, Pore-to-meter scale modeling of heat and mass transport applied to thermal energy storage: How local thermal and velocity fluctuations affect average thermal dispersivity, Energy, Vol: 296, ISSN: 0360-5442

We use a dual-network model to simulate heat and mass transfer in porous media. The model captures pore-scale information in meter-scale simulations and allows for non-equilibrium between the solid and pore space. We apply the model to predict the effective thermal diffusivity in networks representing Bentheimer sandstone, Estaillades limestone and two random packings of monodisperse spheres. Non-Fourier transport at early times can lead to both higher and lower thermal dispersivity than currently assumed using a volume-weighted average of fluid and solid properties. Furthermore, we quantify the mechanical dispersion coefficient caused by differences in local flow velocity, which further contributes to thermal dispersion of the plume. We discuss the results in the context of the design and management of ATES (aquifer thermal energy storage). Ignoring pore-scale velocity and temperature fluctuations in the estimation of averaged properties can lead to errors of more than 50%. The work provides a framework to predict thermal properties of porous media under different flow conditions for more accurate prediction and design of thermal energy storage.

Journal article

Lv X, Yang Y, Lv J, Ji L, Wang J, Wu X, Li Z, Li X, Liu Q, Qi Z, Lin Q, Wu A, Wu HBet al., 2024, Iodine-Mediated C─C Coupling in Neutral Flow Cell for Electrochemical CO<inf>2</inf> Reduction, Advanced Functional Materials, Vol: 34, ISSN: 1616-301X

Carbon utilization efficiency is of vital importance for electrochemical CO2 reduction systems. Proton exchange membrane (PEM) electrolyzers using nonalkaline electrolytes can prevent CO2 crossover and increase carbon utilization efficiency, yet they suffer from unfavored C─C coupling and severe hydrogen evolution. Herein, an iodine-mediated approach to facilitate C─C coupling on Cu-based catalysts toward multi-carbon products in a neutral PEM electrolyzer is reported. By in situ constructing an I-modified Cu surface, the hydrogenation of *CO is promoted and the C─C coupling process progresses through the *CO−*COH pathway with a low energy barrier. A high Faradaic efficiency of ≈72% and a high partial current density of 575 mA cm−2 are achieved for multi-carbon products. The present study demonstrates an efficient approach to developing advanced CO2 electrolyzers for high-value products with high efficiency.

Journal article

Chen S, Shi WK, Yong JY, Zhuang Y, Lin QY, Gao N, Zhang XJ, Jiang Let al., 2023, Numerical study on a structured packed adsorption bed for indoor direct air capture, Energy, Vol: 282, ISSN: 0360-5442

Direct air capture (DAC) for indoor CO2 removal can not only effectively regulate air quality but also improve the capture efficiency to a certain extent, which is a highly feasible win-win solution to decarbonization and human health. This paper proposes a W-shaped packed adsorption bed for indoor direct capture which is optimized and compared with the conventional bed. Firstly, the pressure drop of different adsorption beds is simulated by Darcy-Fochheimer law. The results demonstrate that pressure drop of the W-shaped bed performs better than the conventional adsorption bed. Then temperature swing adsorption process is investigated using an amine functionalization material. It is indicated that energy consumption of the conventional packed bed and the W-shaped packed bed are 236.2 kJ mol−1 and 167.9 kJ mol−1 for CO2 capture process, respectively. Because of the lower pressure drop of the W-shaped bed, energy consumption of fan could be greatly reduced from 88.7 kJ mol−1 to 15.1 kJ mol−1. Finally, a simple indoor CO2 concentration condition model coupled with the reactor CFD model is established to verify the performance of CO2 purification of the reactor, and it shows an excellent regulatory effect on indoor CO2. The concept can provide some valuable insights for DAC in buildings and have the potential of coupling application with various carbon capture systems.

Journal article

Feng R, Xu X, Yu ZT, Lin Qet al., 2023, A machine-learning assisted multi-cluster assessment for decarbonization in the chemical fiber industry toward net-zero: A case study in a Chinese province, Journal of Cleaner Production, Vol: 425, ISSN: 0959-6526

China has pledged to achieve carbon neutrality by 2060, requiring deep decarbonization in its manufacturing sector, aligning with sustainable development goals such as climate action and responsible production. Notably, China's chemical fiber industry contributes over 70% of global production, facing challenges in net-zero transition due to differences in enterprise scale and energy efficiency. This study proposed an assessment framework for the decarbonization pathway for this type of manufacturing industries, use the chemical fiber industry as a case study. A hybrid model based on machine learning was introduced to predict the industry's energy consumption, while multiple-cluster standards were established to assess energy efficiency improvement potential. Monte Carlo simulation was employed to analyze the carbon trading impact on industry decarbonization. Using a Chinese province's chemical fiber industry as a case, results suggest its carbon emissions could reach 1.58 × 107 tCO2 by 2030, and energy efficiency enhancements could reduce emissions by approximately 22.6%. Achieving carbon neutrality would cause the industry to reduce profits by approximately 10%∼15% on higher-priced emissions trading system (ETS), unless additional carbon reduction techniques are adopted. This assessment framework can be applied to study decarbonization transitions in other manufacturing industries.

Journal article

Ghanbarian B, Lin Q, Pires LF, 2023, Scale dependence of tortuosity in soils under contrasting cultivation conditions, Soil and Tillage Research, Vol: 233, ISSN: 0167-1987

Tortuosity is a parameter controlling flow and transport in soils. Under fully saturated and single-phase flow conditions, tortuosity depends not only on porosity but also on the sample volume (or dimension). However, most tortuosity models proposed in the literature ignore the effect of sample size. In this study, we address the scale dependence of tortuosity in soils under two cultivation conditions: conventional tillage (CT) and no tillage (NT). We apply a theoretical model linking tortuosity to porosity (ϕ), critical porosity (ϕc), some fundamental length scale (C), and optimal path fractal dimension (Dopt). To evaluate the theory, we compare theoretical estimations with tortuosity values measured on X-ray microcomputed tomography images of various linear sizes from L = 736.8–36,887.7 µm on 12 soil samples. We demonstrate that the proposed approach accurately estimates the scale dependence of tortuosity in soils. We also find that the theoretical estimations are more accurate for the CT samples than the NT ones. The accuracy of the proposed model is also compared to that of another model derived by assuming that a porous medium consisted of two-dimensional square solid particles. We find that the percolation-based theoretic model estimates tortuosity more precisely than the other model. Our results show that the effect of scale on tortuosity is more profound for the NT samples than the CT ones.

Journal article

Qu M-L, Blunt MJ, Fan X, Foroughi S, Yu Z-T, Lin Qet al., 2023, Pore-to-mesoscale network modeling of heat transfer and fluid flow in packed beds with application to process design, AICHE JOURNAL, ISSN: 0001-1541

Journal article

Xin Q, Yang Y, Liu S, Zhang X, Zheng C, Lin Q, Gao Xet al., 2023, Mass transfer of multi-pollutants over titania-based SCR catalyst: A molecular dynamics study, Applied Energy, Vol: 331, Pages: 1-9, ISSN: 0306-2619

Mass transfer can significantly affect the SCR process which is designed for NOx removal. However, it is still challenging to characterize the transport of gaseous species involved in the process, especially at nano-scale. This work probes into the application of non-equilibrium molecular dynamics (NEMD) simulations to study the mass transfer of multi-pollutants over a titania-based catalyst. A dual control-volume (DCV) model was proposed to simulate transport of typical gaseous molecules (e.g. NO, NH3 and SO2). The impacts of temperature, pore width, hydroxyl sites and competitive diffusion on diffusivity of objective molecules were studied in details. The results showed that temperature and surface sites could affect NH3 more significantly than NO and SO2, yet the influence of surface sites was strongly size-dependent. The reduction in NH3 diffusivity caused by the presence of surface sites decreased from 32.37 % to 2.97 % when the pore width grows from 25 Å to 75 Å. The competitive transport between NH3 and SO2 has also mitigated the impacts of surface sites on both molecules.

Journal article

Blunt MJ, Lin Q, 2022, Flow in Porous Media in the Energy Transition, ENGINEERING, Vol: 14, Pages: 10-14, ISSN: 2095-8099

Journal article

Lin Q, Zhang X, Wang T, Zheng C, Gao Xet al., 2022, Technical Perspective of Carbon Capture, Utilization, and Storage, ENGINEERING, Vol: 14, Pages: 27-32, ISSN: 2095-8099

Journal article

Qu M-L, Lu S-Y, Lin Q, Foroughi S, Yu Z-T, Blunt MJet al., 2022, Characterization of Water Transport in Porous Building Materials Based on an Analytical Spontaneous Imbibition Model, TRANSPORT IN POROUS MEDIA, Vol: 143, Pages: 417-432, ISSN: 0169-3913

Journal article

Garfi G, John CM, Rucker M, Lin Q, Spurin C, Berg S, Krevor Set al., 2022, Determination of the spatial distribution of wetting in the pore networks of rocks, JOURNAL OF COLLOID AND INTERFACE SCIENCE, Vol: 613, Pages: 786-795, ISSN: 0021-9797

Journal article

Zhang Y, Lin Q, Raeini AQ, Onaka Y, Iwama H, Takabayashi K, Blunt MJ, Bijeljic Bet al., 2022, Pore-scale imaging of asphaltene deposition with permeability reduction and wettability alteration, Fuel, Vol: 316, Pages: 1-9, ISSN: 0016-2361

To better understand asphaltene deposition mechanisms and their influence on rock permeability and wettability, we have developed an in situ micro-CT imaging capability to observe asphaltene precipitation during multiphase flow at high resolution in three dimensions. Pure heptane and crude oil were simultaneously injected to induce asphaltene precipitation in the pore space of a sandstone rock sample. The heptane permeability across the sample was nine times lower after the first asphaltene precipitation, while it was reduced by a factor of ninety due to asphaltene migration and growth after subsequent brine injection. Furthermore, through quantifying the curvatures and contact angles on the images before and after asphaltene precipitation, we observed that the wettability of the porous medium changed from water-wet to mixed-wet. Overall, we demonstrate a micro-CT imaging and analysis workflow to quantify asphaltene deposition, permeability reduction and wettability change which can be used for reservoir characterisation and remediation.

Journal article

Wan C, Bao H, Chen Z, Lin Q, Liu S, Wu W, Song H, Yang Yet al., 2022, The prediction of nitric oxide conversion by dielectric barrier discharge using an artificial neural network model, JOURNAL OF THE ENERGY INSTITUTE, Vol: 101, Pages: 96-110, ISSN: 1743-9671

Journal article

Garfi G, John C, Rücker M, Lin Q, Spurin C, Berg S, Krevor Set al., 2022, Determination of the spatial distribution of wetting in the pore networks of rocks

<jats:p>The macroscopic movement of subsurface fluids involved in CO2 storage, groundwater, and petroleum engineering applications is controlled by interfacial forces in the pores of rocks, micrometre to millimetre in length scale. Recent advances in physics based models of these systems has arisen from approaches simulating flow through a digital representation of the complex pore structure. However, further progress is limited by a lack of approaches to characterising the spatial distribution of the wetting state within the pore structure. In this work, we show how observations of the fluid coverage of mineral surfaces within the pores of rocks can be used as the basis for a quantitative 3D characterisation of heterogeneous wetting states throughout rock pore structures. We demonstrate the approach with water-oil fluid pairs on rocks with distinct lithologies (sandstone and carbonate) and wetting states (hydrophilic, intermediate wetting, or heterogeneously wetting). The resulting 3D maps can be used as a deterministic input to pore scale modelling workflows and applied to all multiphase flow problems in porous media ranging from soil science to fuel cells.</jats:p>

Journal article

Alhosani A, Selem AM, Lin Q, Bijeljic B, Blunt MJet al., 2021, Disconnected gas transport in steady‐state three‐phase flow, Water Resources Research, Vol: 57, Pages: 1-26, ISSN: 0043-1397

We use high-resolution three-dimensional X-ray microtomography to investigate fluid displacement during steady-state three-phase flow in a cm-sized water-wet sandstone rock sample. The pressure differential across the sample is measured which enables the determination of relative permeability; capillary pressure is also estimated from the interfacial curvature. Though the measured relative permeabilities are consistent, to within experimental uncertainty, with values obtained without imaging on larger samples, we discover a unique flow dynamics. The most non-wetting phase (gas) is disconnected across the system: gas flows by periodically opening critical flow pathways in intermediate-sized pores. While this phenomenon has been observed in two-phase flow, here it is significant at low flow rates, where capillary forces dominate at the pore-scale. Gas movement proceeds in a series of double and multiple displacement events. Implications for the design of three-phase flow processes and current empirical models are discussed: the traditional conceptualization of three-phase dynamics based on analogies to two-phase flow vastly over-estimates the connectivity and flow potential of the gas phase.

Journal article

Mularczyk A, Lin Q, Niblett D, Vasile A-P, Blunt MJ, Niasar VJ, Marone F, Schmidt TJ, Buechi FN, Eller Jet al., 2021, Capillary Pressure Evolution in Operating Polymer Electrolyte Fuel Cells, ECS Meeting Abstracts, Vol: MA2021-02, Pages: 1027-1027

Journal article

Lin Q, Bijeljic B, Raeini AQ, Rieke H, Blunt MJet al., 2021, Drainage capillary pressure distribution and fluid displacement in a heterogeneous laminated sandstone, Geophysical Research Letters, Vol: 48, Pages: 1-11, ISSN: 0094-8276

We applied three-dimensional X-ray microtomography to image a capillary drainage process (0–1,000 kPa) in a cm-scale heterogeneous laminated sandstone containing three distinct regions with different pore sizes to study the capillary pressure. We used differential imaging to distinguish solid, macropore, and five levels of subresolution pore phases associated with each region. The brine saturation distribution was computed based on average CT values. The nonwetting phase displaced the wetting phase in order of pore size and connectivity. The drainage capillary pressure in the highly heterogeneous rock was dependent on the capillary pressures in the individual regions as well as distance to the boundary between regions. The complex capillary pressure distribution has important implications for accurate water saturation estimation, gas and/or oil migration and the capillary rise of water in heterogeneous aquifers.

Journal article

Mularczyk A, Lin Q, Niblett D, Vasile A, Blunt MJ, Niasar V, Marone F, Schmidt TJ, Büchi FN, Eller Jet al., 2021, Operando liquid pressure determination in polymer electrolyte fuel cells., ACS Applied Materials and Interfaces, Vol: 13, Pages: 34003-34011, ISSN: 1944-8244

Extending the operating range of fuel cells to higher current densities is limited by the ability of the cell to remove the water produced by the electrochemical reaction, avoiding flooding of the gas diffusion layers. It is therefore of great interest to understand the complex and dynamic mechanisms of water cluster formation in an operando fuel cell setting as this can elucidate necessary changes to the gas diffusion layer properties with the goal of minimizing the number, size, and instability of the water clusters formed. In this study, we investigate the cluster formation process using X-ray tomographic microscopy at 1 Hz frequency combined with interfacial curvature analysis and volume-of-fluid simulations to assess the pressure evolution in the water phase. This made it possible to observe the increase in capillary pressure when the advancing water front had to overcome a throat between two neighboring pores and the nuanced interactions of volume and pressure evolution during the droplet formation and its feeding path instability. A 2 kPa higher breakthrough pressure compared to static ex situ capillary pressure versus saturation evaluations was observed, which suggests a rethinking of the dynamic liquid water invasion process in polymer electrolyte fuel cell gas diffusion layers.

Journal article

Lin Q, Bijeljic B, Foroughi S, Berg S, Blunt MJet al., 2021, Pore-scale imaging of displacement patterns in an altered-wettability carbonate, Chemical Engineering Science, Vol: 235, Pages: 1-12, ISSN: 0009-2509

High-resolution X-ray imaging combined with a steady-state flow experiment is used to demonstrate how pore-scale displacement affects macroscopic properties in an altered-wettability microporous carbonate, where porosity and fluid saturation can be directly obtained from the grey-scale micro-CT images. The resolvable macro pores are largely oil-wet with an average thermodynamic contact angle of 120°. The pore-by-pore analysis shows locally either oil or brine almost fully occupied the macro pores, with some oil displacement in the micro-porosity. We observed a typical oil-wet behaviour consistent with the contact angle measurement. The brine tended to occupy the larger macro pores, leading to a higher brine relative permeability, lower residual oil saturation, than under water-wet conditions and in a mixed-wet sandstone. The capillary pressure was negative and seven times larger in the carbonate than the sandstone, despite having a similar average pore size. These different displacement patterns are principally determined by the difference in wettability.

Journal article

Zhang Y, Bijeljic B, Gao Y, Lin Q, Blunt MJet al., 2021, Quantification of non‐linear multiphase flow in porous media, Geophysical Research Letters, Vol: 48, Pages: 1-7, ISSN: 0094-8276

We measure the pressure difference during two‐phase flow across a sandstone sample for a range of injection rates and fractional flows of water, the wetting phase, during an imbibition experiment. We quantify the onset of a transition from a linear relationship between flow rate and pressure gradient to a nonlinear power‐law dependence. We show that the transition from linear (Darcy) to nonlinear flow and the exponent in the power‐law is a function of fractional flow. We use energy balance to accurately predict the onset of intermittency for a range of fractional flows, fluid viscosities, and different rock types.

Journal article

Alhosani A, Lin Q, Scanziani A, Andrews E, Zhang K, Bijeljic B, Blunt MJet al., 2021, Pore-scale characterization of carbon dioxide storage at immiscible and near-miscible conditions in altered-wettability reservoir rocks, International Journal of Greenhouse Gas Control, Vol: 105, Pages: 1-15, ISSN: 1750-5836

Carbon dioxide storage combined with enhanced oil recovery (CCS-EOR) is an important approach for reducing greenhouse gas emissions. We use pore-scale imaging to help understand CO2 storage and oil recovery during CCS-EOR at immiscible and near-miscible CO2 injection conditions. We study in situ immiscible CO2 flooding in an oil-wet reservoir rock at elevated temperature and pressure using X-ray micro-tomography. We observe the predicted, but hitherto unreported, three-phase wettability order in strongly oil-wet rocks, where water occupies the largest pores, oil the smallest, while CO2 occupies pores of intermediate size. We investigate the pore occupancy, existence of CO2 layers, recovery and CO2 trapping in the oil-wet rock at immiscible conditions and compare to the results obtained on the same rock type under slightly more weakly oil-wet near-miscible conditions, with the same wettability order. CO2 spreads in connected layers at near-miscible conditions, while it exists as disconnected ganglia in medium-sized pores at immiscible conditions. Hence, capillary trapping of CO2 by oil occurs at immiscible but not at near-miscible conditions. Moreover, capillary trapping of CO2 by water is not possible in both cases since CO2 is more wetting to the rock than water. The oil recovery by CO2 injection alone is reduced at immiscible conditions compared to near-miscible conditions, where low gas-oil capillary pressure improves microscopic displacement efficiency. Based on these results, to maximize the amount of oil recovered and CO2 stored at immiscible conditions, a water-alternating-gas injection strategy is suggested, while a strategy of continuous CO2 injection is recommended at near-miscible conditions.

Journal article

Blunt MJ, Alhosani A, Lin Q, Scanziani A, Bijeljic Bet al., 2021, Determination of contact angles for three-phase flow in porous media using an energy balance, Journal of Colloid and Interface Science, Vol: 582, Pages: 283-290, ISSN: 0021-9797

HYPOTHESIS: We define contact angles, θ, during displacement of three fluid phases in a porous medium using energy balance, extending previous work on two-phase flow. We test if this theory can be applied to quantify the three contact angles and wettability order in pore-scale images of three-phase displacement. THEORY: For three phases labelled 1, 2 and 3, and solid, s, using conservation of energy ignoring viscous dissipation (Δa1scosθ12-Δa12-ϕκ12ΔS1)σ12=(Δa3scosθ23+Δa23-ϕκ23ΔS3)σ23+Δa13σ13, where ϕ is the porosity, σ is the interfacial tension, a is the specific interfacial area, S is the saturation, and κ is the fluid-fluid interfacial curvature. Δ represents the change during a displacement. The third contact angle, θ13 can be found using the Bartell-Osterhof relationship. The energy balance is also extended to an arbitrary number of phases. FINDINGS: X-ray imaging of porous media and the fluids within them, at pore-scale resolution, allows the difference terms in the energy balance equation to be measured. This enables wettability, the contact angles, to be determined for complex displacements, to characterize the behaviour, and for input into pore-scale models. Two synchrotron imaging datasets are used to illustrate the approach, comparing the flow of oil, water and gas in a water-wet and an altered-wettability limestone rock sample. We show that in the water-wet case, as expected, water (phase 1) is the most wetting phase, oil (phase 2) is intermediate wet, while gas (phase 3) is most non-wetting with effective contact angles of θ12≈48° and θ13≈44°, while θ23=0 since oil is always present in spreading layers. In contrast, for the altered-wettability case, oil is most wetting, gas is intermediate-wet, while water is most non-wetting with contact angles of θ12=134°±~10°,θ13=119°&p

Journal article

Blunt M, Kearney L, Alhosani A, Lin Q, Bijeljic Bet al., 2021, Wettability characterization from pore-scale images using topology and energy balance with implications for recovery and storage

We present two methods to measure contact angles inside porous media using high-resolution images. The direct determination of contact angle at the three-phase contact line is often ambiguous due to uncertainties with image segmentation. Instead, we propose two alternative approaches that provide an averaged assessment of wettability. The first uses fundamental principles in topology to relate the contact angle to the integral of the Gaussian curvature over the fluid-fluid meniscus. The advantage of this approach is that it replaces the uncertain determination of an angle at a point with a more accurate determination of an integral over a surface. However, in mixed-wet porous media, many interfaces are pinned with a hinging contact angle. For predictive pore-scale models, we need to determine the contact angle at which displacement occurs when the interfaces move. To address this problem we apply an energy balance, ignoring viscous dissipation, to estimate the contact angle from the meniscus curvature and changes in interfacial areas and saturation. We apply these methods to characterize wettability on pore-scale images of two- and three-phase flow. We also discuss the implications of the results for recovery and storage applications.

Conference paper

Lin Q, Akai T, Blunt MJ, Bijeljic B, Iwama H, Takabayashi K, Onaka Y, Yonebayashi Het al., 2021, Pore-scale imaging of asphaltene-induced pore clogging in carbonate rocks, Fuel, Vol: 283, ISSN: 0016-2361

We propose an experimental methodology to visualize asphaltene precipitation in the pore space of rocks and assess the reduction in permeability. We perform core flooding experiments integrated with X-ray microtomography (micro-CT). The simultaneous injection of pure heptane and crude oil containing asphaltene induces the precipitation of asphaltene in the pore space. The degree of precipitation is controlled by the measurement of differential pressure across the sample. After precipitation, doped heptane is injected to replace the fluid to enhance the contrast between precipitated asphaltene and doped heptane. The micro-CT images are segmented into three phases: void, precipitated asphaltene, and rock. In the experiment, we observed that the precipitated asphaltene which occupied 39.1% of the pore volume caused a 29-fold reduction in permeability. Furthermore, we analyze the spatial distribution of precipitated asphaltene which showed that the asphaltene tended to clog the larger pores. We also computed the flow field numerically on the images and obtained good agreement between simulated and measured permeability. The distribution of local velocity showed that after precipitation the flow was confined to narrow channels in the pore space. This method can be applied to any type of porous system with precipitation.

Journal article

Selem A, Agenet N, Gao Y, Lin Q, Blunt MJ, Bijeljic Bet al., 2021, PORE-SCALE IMAGING OF CONTROLLED-SALINITY WATERFLOODING IN A HETEROGENEOUS CARBONATE ROCK AT RESERVOIR CONDITIONS, Pages: 2272-2276

Controlled salinity water-flooding (CSW) is a promising enhanced oil recovery technique, yet the pore-scale mechanisms that control the process remain poorly understood especially in carbonate rocks. The aim of this experimental study is, therefore, to gain novel insights into CSW and characterize oil, water and the pore space in carbonates. X-ray imaging combined with a high-pressure high-temperature flow apparatus was used to image and study in situ CSW in a complex carbonate rock. To establish the conditions found in oil reservoirs, the Estaillades limestone core sample (5.9 mm in diameter and 10 mm in length) was aged for three weeks at 11 MPa and 80°C. This weakly oil-wet sample was then flooded by injecting low salinity brine at a range of increasing flow rates. Tomographic images were acquired at 2.9-micron spatial resolution after each flow rate. A total of 60 pore volumes of low salinity brine were injected recovering 85% of the oil initially in place in macro-pores. Contact angles and brine-oil curvatures were obtained to characterize wettability changes within the rock pore space. Our analysis shows that wettability alteration towards a mixed wet system caused by low salinity brine was the main mechanism for increased oil recovery.

Conference paper

Alhosani A, Scanziani A, Lin Q, Selem A, Pan Z, Blunt MJ, Bijeljic Bet al., 2020, Three-phase flow displacement dynamics and Haines jumps in a hydrophobic porous medium, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol: 476, ISSN: 1364-5021

We use synchrotron X-ray micro-tomography to investigate the displacement dynamics during three-phase—oil, water and gas—flow in a hydrophobic porous medium. We observe a distinct gas invasion pattern, where gas progresses through the pore space in the form of disconnected clusters mediated by double and multiple displacement events. Gas advances in a process we name three-phase Haines jumps, during which gas re-arranges its configuration in the pore space, retracting from some regions to enable the rapid filling of multiple pores. The gas retraction leads to a permanent disconnection of gas ganglia, which do not reconnect as gas injection proceeds. We observe, in situ, the direct displacement of oil and water by gas as well as gas–oil–water double displacement. The use of local in situ measurements and an energy balance approach to determine fluid–fluid contact angles alongside the quantification of capillary pressures and pore occupancy indicate that the wettability order is oil–gas–water from most to least wetting. Furthermore, quantifying the evolution of Minkowski functionals implied well-connected oil and water, while the gas connectivity decreased as gas was broken up into discrete clusters during injection. This work can be used to design CO2 storage, improved oil recovery and microfluidic devices.

Journal article

Akai T, Lin Q, Bijeljic B, Blunt MJet al., 2020, Using energy balance to determine pore-scale wettability, Journal of Colloid and Interface Science, Vol: 576, Pages: 486-495, ISSN: 0021-9797

HypothesisBased on energy balance during two-phase displacement in porous media, it has recently been shown that a thermodynamically consistent contact angle can be determined from micro-tomography images. However, the impact of viscous dissipation on the energy balance has not been fully understood. Furthermore, it is of great importance to determine the spatial distribution of wettability. We use direct numerical simulation to validate the determination of the thermodynamic contact angle both in an entire domain and on a pore-by-pore basis.SimulationsTwo-phase direct numerical simulations are performed on complex 3D porous media with three wettability states: uniformly water-wet, uniformly oil-wet, and non-uniform mixed-wet. Using the simulated fluid configurations, the thermodynamic contact angle is computed, then compared with the input contact angles.FindingsThe impact of viscous dissipation on the energy balance is quantified; it is insignificant for water flooding in water-wet and mixed-wet media, resulting in an accurate estimation of a representative contact angle for the entire domain even if viscous effects are ignored. An increasing trend in the computed thermodynamic contact angle during water injection is shown to be a manifestation of the displacement sequence. Furthermore, the spatial distribution of wettability can be represented by the thermodynamic contact angle computed on a pore-by-pore basis.

Journal article

Scanziani A, Alhosani A, Lin Q, Spurin C, Garfi G, Blunt MJ, Bijeljic Bet al., 2020, In situ characterization of three‐phase flow in mixed‐wet porous media using synchrotron imaging, Water Resources Research, Vol: 56, ISSN: 0043-1397

We use fast synchrotron X‐ray microtomography to understand three‐phase flow in mixed‐wet porous media to design either enhanced permeability or capillary trapping. The dynamics of these phenomena are of key importance in subsurface hydrology, carbon dioxide storage, oil recovery, food and drug manufacturing, and chemical reactors. We study the dynamics of a water‐gas‐water injection sequence in a mixed‐wet carbonate rock. During the initial waterflooding, water displaced oil from pores of all size, indicating a mixed‐wet system with local contact angles both above and below 90°. When gas was injected, gas displaced oil preferentially with negligible displacement of water. This behavior is explained in terms of the gas pressure needed for invasion. Overall, gas behaved as the most nonwetting phase with oil as the most wetting phase; however, pores of all size were occupied by oil, water, and gas, as a signature of mixed‐wet media. Thick oil wetting layers were observed, which increased oil connectivity and facilitated its flow during gas injection. A chase waterflooding resulted in additional oil flow, while gas was trapped by oil and water. Furthermore, we quantified the evolution of the surface areas and both Gaussian and the total curvature, from which capillary pressure could be estimated. These quantities are related to the Minkowski functionals which quantify the degree of connectivity and trapping. The combination of water and gas injection, under mixed‐wet immiscible conditions, leads to both favorable oil flow and significant trapping of gas, which is advantageous for storage applications.

Journal article

Zhang Y, Bijeljic B, Gao Y, Lin Q, Blunt Met al., 2020, Quantification of non-linear multiphase flow in porous media

Working paper

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