Representative Elementary Volume Determination for Permeability and Porosity Using Numerical Three-Dimensional Experiments in Microtomography Data

ABSTRACT. Characterization of carbonate rocks presents several challenges regarding the acquisition of petrophysical parameters and the understanding of fluid-flow dynamics in their pore system. To face these challenges, techniques such as X-ray microtomography, three-dimensional digital model reconstruction and fluid-flow numerical simulations have been continuously developed and improved. This study analyzes the representative elementary volume (REV) of a region of interest (ROI) of a highly heterogeneous stromatolite sample. Porosity and permeability are estimated for different subvolumes of the sample based on digital petrophysics. All necessary steps for reconstruction and segmentation of the complex pore system of the sample, as well as numerical simulations of fluid flow, are presented and discussed. The workflow is promising for reservoir evaluation because it can be applied to any type of carbonate rock.Keywords: Stromatolite, mCT, segmentation, REV, digital petrophysicsRESUMO. A caracterização de rochas carbonáticas apresenta diversos desafios quanto à determinação de seus parâmetros petrofísicos e o entendimento da dinâmica de escoamento de fluidos em seus sistemas porosos. Técnicas como a microtomografia de raios X, a modelagem digital tridimensional e a simulação numérica do escoamento de fluidos têm sido continuamente desenvolvidas e aprimoradas para superar esses desafios. Este estudo analisa o volume elementar representativo (REV) em uma região de interesse (ROI) de uma amostra de estromatólito altamente heterogênea. A porosidade e a permeabilidade são estimadas em diferentes subvolumes da amostra através da petrofísica digital. São apresentadas e discutidas todas as etapas necessárias para a reconstrução e segmentação do sistema poroso e a simulação numérica do escoamento de fluidos. A metodologia é promissora para avalição de reservatórios visto que o fluxo de trabalho pode ser aplicado a qualquer tipo de rocha carbonática.Palavras-chave: Estromatólitos, mCT, segmentação, REV, petrofísica digital

Download Full-text

Effect of Saturation and Image Resolution on Representative Elementary Volume and Topological Quantification: An Experimental Study on Bentheimer Sandstone Using Micro-CT

Transport in Porous Media ◽

10.1007/s11242-021-01571-9 ◽

2021 ◽

Author(s):

Ruotong Huang ◽

Anna L. Herring ◽

Adrian Sheppard

Keyword(s):

Experimental Study ◽

Representative Elementary Volume ◽

Image Resolution ◽

Micro Ct ◽

Elementary Volume

Download Full-text

New insights on homogenization for hexagonal-shaped composites as Cosserat continua

Meccanica ◽

10.1007/s11012-021-01355-x ◽

2021 ◽

Author(s):

Marco Colatosti ◽

Nicholas Fantuzzi ◽

Patrizia Trovalusci ◽

Renato Masiani

Keyword(s):

Continuum Theory ◽

Representative Elementary Volume ◽

Elementary Volume ◽

Displacement Fields ◽

Micropolar Continuum ◽

Rigid Particles ◽

Hexagonal Shape ◽

Classical Models ◽

Elastic Interfaces ◽

Cosserat Continua

AbstractIn this work, particle composite materials with different kind of microstructures are analyzed. Such materials are described as made of rigid particles and elastic interfaces. Rigid particles of arbitrary hexagonal shape are considered and their geometry is described by a limited set of parameters. Three different textures are analyzed and static analyses are performed for a comparison among the solutions of discrete, micropolar (Cosserat) and classical models. In particular, the displacements of the discrete model are compared to the displacement fields of equivalent micropolar and classical continua realized through a homogenization technique, starting from the representative elementary volume detected with a numeric approach. The performed analyses show the effectiveness of adopting the micropolar continuum theory for describing such materials.

Download Full-text

Estimating the Effect of Fractal Dimension on Representative Elementary Volume of Randomly Distributed Rock Fracture Networks

Geofluids ◽

10.1155/2018/7206074 ◽

2018 ◽

Vol 2018 ◽

pp. 1-13 ◽

Cited By ~ 1

Author(s):

Jing Zhang ◽

Liyuan Yu ◽

Hongwen Jing ◽

Richeng Liu

Keyword(s):

Fractal Dimension ◽

Functional Relationship ◽

Rock Fracture ◽

Representative Elementary Volume ◽

Width Ratio ◽

Elementary Volume ◽

Equivalent Permeability ◽

Length Width ◽

Rock Fracture Networks

The effect of fractal dimension (Df) on the determination of representative elementary volume (REV) was investigated through numerical experimentations, in which a new method was adopted to extract submodels that have different length-width ratios from original discrete facture networks (DFNs). Fluid flow in 1610 DFNs with different geometric characteristics of fractures and length-width ratios was simulated, and the equivalent permeability was calculated. The results show that the average equivalent permeability (KREV) at the REV size for DFNs increases with the increase in Df. The KREV shows a downward trend with increasing length-width ratio of the submodel. A strong exponent functional relationship is found between the REV size and Df. The REV size decreases with increasing Df. With the increment of the length-width ratio of submodels, the REV size shows a decreasing trend. The effects of length-width ratio and Df on the REV size can be negligible when Df≥1.5, but are significant when Df<1.5.

Download Full-text

Determination of representative elementary volume (REV) for jointed rock masses exhibiting scale-dependent behavior: A numerical investigation

10.21203/rs.3.rs-847473/v1 ◽

2021 ◽

Author(s):

Mehmet Sari

Keyword(s):

Jointed Rock ◽

Representative Elementary Volume ◽

Elementary Volume ◽

Rock Masses ◽

Continuum Approach ◽

Joint Spacing ◽

Jointed Rock Masses ◽

Equivalent Continuum ◽

Equivalent Continuum Approach

Abstract Representative elementary volume (REV) is defined as the usual size of a rock mass structure beyond which its mechanical properties are homogenous and isotropic, and its behavior can be modeled using the equivalent continuum approach. Determination of REV is a complex problem in rock engineering due to its definition ambiguity and application area. This study is one of the first attempts to define a REV for jointed rock masses using the equivalent continuum approach. It is aimed to numerically search a ratio between the characteristic size of an engineering structure and pre-existing joint spacing, which are the two most important contributing elements in assessing REV. For this purpose, four hypothetical engineering cases were investigated using the RS2 (Phase2 v. 9.0) finite element (FE) analysis program. An underground circular opening with a constant diameter, an open-pit mine with varying bench heights, a single bench with a constant height, and an underground powerhouse cavern with a known dimension were executed for possible changes in the safety factor and total displacement measurements under several joint spacing values. Different cut-off REVs were calculated for FE models depending on the type of excavation and measurement method. An average REV size of 19.0, ranging between a minimum of 2 for tunnels and a maximum of 48 for slopes, was found in numerical analysis. The calculated sizes of REV were significantly larger than the range of values (5 to 10) commonly reported in the relevant geotechnical literature.

Download Full-text

Upscaling of elastic properties in carbonates: A modeling approach based on a multiscale geophysical data set

10.5194/egusphere-egu2020-18106 ◽

2020 ◽

Author(s):

Jerome Fortin ◽

Cedric Bailly ◽

Mathilde Adelinet ◽

Youri Hamon

Keyword(s):

Elastic Properties ◽

Wave Velocity ◽

Representative Elementary Volume ◽

P Wave ◽

Elementary Volume ◽

Data Set ◽

Wave Velocities ◽

P Wave Velocity ◽

Ultrasonic Measurements ◽

Seismic Scale

<p>Linking ultrasonic measurements made on samples, with sonic logs and seismic subsurface data, is a key challenge for the understanding of carbonate reservoirs. To deal with this problem, we investigate the elastic properties of dry lacustrine carbonates. At one study site, we perform a seismic refraction survey (100 Hz), as well as sonic (54 kHz) and ultrasonic (250 kHz) measurements directly on outcrop and ultrasonic measurements on samples (500 kHz). By comparing the median of each data set, we show that the P wave velocity decreases from laboratory to seismic scale. Nevertheless, the median of the sonic measurements acquired on outcrop surfaces seems to fit with the seismic data, meaning that sonic acquisition may be representative of seismic scale. To explain the variations due to upscaling, we relate the concept of representative elementary volume with the wavelength of each scale of study. Indeed, with upscaling, the wavelength varies from millimetric to pluri-metric. This change of scale allows us to conclude that the behavior of P wave velocity is due to different geological features (matrix porosity, cracks, and fractures) related to the different wavelengths used. Based on effective medium theory, we quantify the pore aspect ratio at sample scale and the crack/fracture density at outcrop and seismic scales using a multiscale representative elementary volume concept. Results show that the matrix porosity that controls the ultrasonic P wave velocities is progressively lost with upscaling, implying that crack and fracture porosity impacts sonic and seismic P wave velocities, a result of paramount importance for seismic interpretation based on deterministic approaches.</p><p>Bailly, C., Fortin, J., Adelinet, M., & Hamon, Y. (2019). Upscaling of elastic properties in carbonates: A modeling approach based on a multiscale geophysical data set. Journal of Geophysical Research: Solid Earth, 124. https://doi.org/10.1029/2019JB018391</p>

Download Full-text