Anchoring Multi‐Scale Models to Micron‐Scale Imaging of Multiphase Flow in Rocks

Wang, Shan; Ruspini, Leonardo C.; Øren, Pål‐Eric; Offenwert, Stefanie Van; Bultreys, Tom

doi:10.1029/2021wr030870

Cited by 13 publications

(16 citation statements)

References 52 publications

(79 reference statements)

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“…In order to reduce segmentation errors, macropores were first segmented manually on the dry scan using histogram thresholding. The differential imaging method (subtracting dry scans from brine-saturated scans) (Lin et al, 2016;Wang et al, 2022) was used to identify microporous regions. Then, the rest of the voxels in the dry scan were assigned as solid grain phase.…”

Section: Image Processingmentioning

confidence: 99%

“…Figure 2 shows the three phase segmentation results. For multiphase scans, manuscript submitted to Water Resources Research 9 the decane and brine within macropores were also classified with histogram thresholding, on which the labelled macro-pore space was used as a mask (Wang et al, 2022).…”

Section: Image Processingmentioning

confidence: 99%

“…Similarly, the saturation distribution map can also be obtained with multiphase-dry differential image. The full details are provided in our previous publication (Wang et al, 2022).…”

Section: Image Processingmentioning

confidence: 99%

“…Therefore, the presence manuscript submitted to Water Resources Research 22 of microporosity increases the complexity of the pore space architecture, which may play an important role in the multiphase flow. For the determination of the rock type map, we introduced a method based on micro-CT images of obtained during capillary pressure experiments in (Wang et al, 2022). The method was validated to be a promising approach in decreasing the uncertainty of modelling, and was therefore used here.…”

Section: Multi-scale Pore Network Extractionmentioning

confidence: 99%

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Imaging and modelling the impact of multi-scale pore connectivity on two-phase flow in mixed-wet rock

Wang

Mascini

Ruspini

et al. 2022

Preprint

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The wetting properties of pore walls have a strong effect on multiphase flow through porous media. However, the fluid flow behaviour in porous materials with both complex pore structures and non-uniform wettability are still unclear. Here, we performed unsteady-state quasi-static oil- and waterflooding experiments to study multiphase flow in two sister heterogeneous sandstones with variable wettability conditions (i.e. one natively water-wet and one chemically treated to be mixed-wet). The pore-scale fluid distributions during this process were imaged by laboratory-based X-ray micro-computed tomography (micro-CT). In the mixed-wet case, we observed pore filling events where the fluid interface appeared to be at quasi-equilibrium at every position along the pore body (13% by volume), in contrast to capillary instabilities typically associated with slow drainage or imbibition. These events corresponded to slow displacements previously observed in unsteady-state experiments, explaining the wide range of displacement time scales in mixed-wet samples. Our new data allowed us to quantify the fluid saturations below the image resolution, indicating that slow events were caused by the presence of microporosity and the wetting heterogeneity. Finally, we investigated the sensitivity of the multi-phase flow properties to the slow filling events using a state-of-the-art multi-scale pore network model. This indicated that pores where such events took place contributed up to 19% of the sample’s total absolute permeability, but that the impact on the relative permeability may be smaller. Our study sheds new light on poorly understood multiphase fluid dynamics in complex rocks, of interest to e.g. groundwater remediation and subsurface CO2 storage.

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Section: Image Processingmentioning

confidence: 99%

Section: Image Processingmentioning

confidence: 99%

“…Similarly, the saturation distribution map can also be obtained with multiphase-dry differential image. The full details are provided in our previous publication (Wang et al, 2022).…”

Section: Image Processingmentioning

confidence: 99%

Section: Multi-scale Pore Network Extractionmentioning

confidence: 99%

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Imaging and modelling the impact of multi-scale pore connectivity on two-phase flow in mixed-wet rock

Wang

Mascini

Ruspini

et al. 2022

Preprint

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“…Furthermore, the DRP technique can be employed to simulate multiphase flow in core samples (Ruspini et al, 2021;S. Wang et al, 2022).…”

mentioning

confidence: 99%

Predictive Soft Computing Methods for Building Digital Rock Models Verified by Positron Emission Tomography Experiments

Ebadi

Armstrong

Mostaghimi

et al. 2022

Water Resources Research

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The influence of core‐scale heterogeneity on continuum‐scale flow and laboratory measurements are not well understood. To address this issue, we propose a fully automated workflow based on soft computing to characterize the heterogeneous flow properties of cores for predictive continuum‐scale models. While the proposed AI‐based workflow inherently has no trained knowledge of rock petrophysical properties, our results demonstrate that image features and morphological properties provide sufficient measures for petrophysical classification. Micro X‐ray computed tomography (μxCT) image features were extracted from full core plug images by using a Convolutional Neural Network and Minkowski functional measurements. The features were then classified into specific classes using Principal Component Analysis followed by K‐means clustering. Next, the petrophysical properties of each class were evaluated using pore‐scale simulations to substantiate that unique classes were identified. The μxCT image was then up‐scaled to a continuum‐scale grid based on the defined classes. Last, simulation results were evaluated against real‐time flooding data monitored by Positron Emission Tomography. Both homogeneous sandstone and heterogeneous carbonate were tested. Simulation and experimental saturation profiles compared well, demonstrating that the workflow provided high‐fidelity characterization. Overall, we provided a novel workflow to build digital rock models in a fully automated way to better understand the impacts of heterogeneity on flow.

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A Closed-Form Equation for Capillary Pressure in Porous Media for All Wettabilities

Foroughi

Bijeljic²,

Blunt³

2022

Transp Porous Med

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A saturation–capillary pressure relationship is proposed that is applicable for all wettabilities, including mixed-wet and oil-wet or hydrophobic media. This formulation is more flexible than existing correlations that only match water-wet data, while also allowing saturation to be written as a closed-form function of capillary pressure: we can determine capillary pressure explicitly from saturation, and vice versa. We propose $$P_{{\text{c}}} = A + B\tan \left( {\frac{\pi }{2} - \pi S_{e}^{C} } \right)\,{\text{for}}\,0 \le S_{{\text{e}}} \le 1,$$ P c = A + B tan π 2 - π S e C for 0 ≤ S e ≤ 1 , where $$S_{{\text{e}}}$$ S e is the normalized saturation. A indicates the wettability: $$A>0$$ A > 0 is a water-wet medium, $$A<0$$ A < 0 is hydrophobic while small A suggests mixed wettability. B represents the average curvature and pore-size distribution which can be much lower in mixed-wet compared to water-wet media with the same pore structure if the menisci are approximately minimal surfaces. C is an exponent that controls the inflection point in the capillary pressure and the asymptotic behaviour near end points. We match the model accurately to 29 datasets in the literature for water-wet, mixed-wet and hydrophobic media, including rocks, soils, bead and sand packs and fibrous materials with over four orders of magnitude difference in permeability and porosities from 20% to nearly 90%. We apply Leverett J-function scaling to make the expression for capillary pressure dimensionless and discuss the behaviour of analytical solutions for spontaneous imbibition.

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Anchoring Multi‐Scale Models to Micron‐Scale Imaging of Multiphase Flow in Rocks

Cited by 13 publications

References 52 publications

Imaging and modelling the impact of multi-scale pore connectivity on two-phase flow in mixed-wet rock

Imaging and modelling the impact of multi-scale pore connectivity on two-phase flow in mixed-wet rock

Predictive Soft Computing Methods for Building Digital Rock Models Verified by Positron Emission Tomography Experiments

A Closed-Form Equation for Capillary Pressure in Porous Media for All Wettabilities

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