Multiphase-flow properties of fractured porous media

Rangel-German, Edgar; Akın, Serhat; Castanier, L.M.

doi:10.1016/j.petrol.2005.12.010

Cited by 33 publications

(7 citation statements)

References 13 publications

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“…In the past, in situ imaging of experiments based on CT technologies was applied to a wide range of studies including geomechanical behavior of fractures (Re and Scavia, 1999), evaluations of triaxial tests (Feng et al, 2004;Ge et al, 2001;Lenoir et al, 2007;Ren and Ge, 2004;Vinegar et al, 1991;Zhou et al, 2008), shear tests (Tatone and Grasselli, 2015), sand production experiments (Santos et al, 2010) as well as various single-/multi-phase core-flooding experiments in fractured and unfractured rocks (Huo and Benson, 2015;Krevor et al, 2012;Oh et al, 2013;Perrin and Benson, 2010;Pini and Benson, 2013;Pini et al, 2012;Rangel-German et al, 2006;Schembre and Kovscek, 2003;Shi et al, 2009;Watanabe et al, 2011). CT technology generally represents a 3-D non-destructive method to image material contrasts in high resolution and, therefore, is well suited to reproduce dynamic processes in situ and in "real time".…”

Section: Introductionmentioning

confidence: 99%

Simulating stress-dependent fluid flow in a fractured core sample using real-time X-ray CT data

et al. 2016

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Abstract. Various geoscientific applications require a fast prediction of fracture permeability for an optimal workflow. Hence, the objective of the current study is to introduce and validate a practical method to characterize and approximate single flow in fractures under different stress conditions by using a core-flooding apparatus, in situ X-ray computed tomography (CT) scans and a finite-volume method solving the Navier-Stokes-Brinkman equations. The permeability of the fractured sandstone sample was measured stepwise during a loading-unloading cycle (0.7 to 22.1 MPa and back) to validate the numerical results. Simultaneously, the pressurized core sample was imaged with a medical X-ray CT scanner with a voxel dimension of 0.5 × 0.5 × 1.0 mm 3 . Fracture geometries were obtained by CT images based on a modification of the simplified missing attenuation (MSMA) approach. Simulation results revealed both qualitative plausibility and a quantitative approximation of the experimentally derived permeabilities. The qualitative results indicate flow channeling along several preferential flow paths with less pronounced tortuosity. Significant changes in permeability can be assigned to temporal and permanent changes within the fracture due to applied stresses. The deviations of the quantitative results appear to be mainly caused by both local underestimation of hydraulic properties due to compositional matrix heterogeneities and the low CT resolution affecting the accurate capturing of sub-grid-scale features. Both affect the proper reproduction of the actual connectivity and therefore also the depiction of the expected permeability hysteresis. Furthermore, the threshold value CT mat (1862.6 HU) depicting the matrix material represents the most sensitive input parameter of the simulations. Small variations of CT mat can cause enormous changes in simulated permeability by up to a factor of 2.6 ± 0.1 and, thus, have to be defined with caution. Nevertheless, comparison with further CT-based flow simulations indicates that the proposed method represents a valuable method to approximate actual permeabilities, particularly for smooth fractures (< 35 µm). However, further systematic investigations concerning the applicability of the method are essential for future studies. Thus, some recommendations are compiled by also including suggestions of comparable studies.

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Section: Introductionmentioning

confidence: 99%

Simulating stress-dependent fluid flow in a fractured core sample using real-time X-ray CT data

et al. 2016

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“…In Section 3.3, we examine fracture geometries by evaluating the distributions of the fracture aperture and the total void volume of the fracture. Aperture distributions are relevant because these distributions provide insights about permeability evolution [20], channelization [55], geomechanical strain [77], and fluid imbibition and drainage [78] in fractured core experiments. As to the fracture void volume, it provides insights about mineral dissolution in reactive flow experiments [40].…”

Section: Resultsmentioning

confidence: 99%

Quantifying fracture geometry with X-ray tomography: Technique of Iterative Local Thresholding (TILT) for 3D image segmentation

2016

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This paper presents a new method-the Technique of Iterative Local Thresholding (TILT)-for processing 3D X-ray computed tomography (xCT) images for visualization and quantification of rock fractures. The TILT method includes the following advancements. First, custom masks are generated by a fracture-dilation procedure, which significantly amplifies the fracture signal on the intensity histogram used for local thresholding. Second, TILT is particularly well suited for fracture characterization in granular rocks because the multi-scale Hessian fracture (MHF) filter has been incorporated to distinguish fractures from pores in the rock matrix. Third, TILT wraps the thresholding and fracture isolation steps in an optimized iterative routine for binary segmentation, minimizing human intervention and enabling automated processing of large 3D datasets. As an illustrative example, we applied TILT to 3D xCT images of reacted and unreacted fractured limestone cores. Other segmentation methods were also applied to provide insights regarding variability in image processing. The results show that TILT significantly enhanced separability of grayscale intensities, outperformed the other methods in automation, and was successful in isolating fractures from the porous rock matrix. Because the other methods are more likely to misclassify fracture edges as void and/or have limited capacity in distinguishing fractures from pores, those methods estimated larger fracture volumes (up to 80 %), surface areas (up to 60 %), and roughness (up to a factor of 2). These differences in fracture geometry would lead to significant disparities in hydraulic permeability predictions, as determined by 2D flow simulations.

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“…Pan et al [49] suggested that the slope of 0.6 for air and 0.7 for water relative permeability functions give rise to better match to experimental data. While, Rangel-German et al [50] obtained the slope of 0.6 for both air and water relative permeabilities. Replacement of the unity slope of the X-curve model by smaller slopes in these works is an indication of occurrence of higher flow resistance in fractures because of strong interference between the flowing phases.…”

Section: Literature Reviewmentioning

confidence: 91%

Analytical Estimation of Water-Oil Relative Permeabilities through Fractures

Saboorian‐Jooybari

2015

Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles

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-Modeling multiphase flow through fractures is a key issue for understanding flow mechanism and performance prediction of fractured petroleum reservoirs, geothermal reservoirs, underground aquifers and carbon-dioxide sequestration. One of the most challenging subjects in modeling of fractured petroleum reservoirs is quantifying fluids competition for flow in fracture network (relative permeability curves). Unfortunately, there is no standard technique for experimental measurement of relative permeabilities through fractures and the existing methods are very expensive, time consuming and erroneous. Although, several formulations were presented to calculate fracture relative permeability curves in the form of linear and power functions of flowing fluids saturation, it is still unclear what form of relative permeability curves must be used for proper modeling of flow through fractures and consequently accurate reservoir simulation. Basically, the classic linear relative permeability (X-type) curves are used in almost all of reservoir simulators. In this work, basic fluid flow equations are combined to develop a new simple analytical model for water-oil two phase flow in a single fracture. The model gives rise to simple analytic formulations for fracture relative permeabilities. The model explicitly proves that water-oil relative permeabilities in fracture network are functions of fluids saturation, viscosity ratio, fluids density, inclination of fracture plane from horizon, pressure gradient along fracture and rock matrix wettability, however they were considered to be only functions of saturations in the classic X-type and power (Corey [35] and Honarpour et al. [28,29]) models. Eventually, validity of the proposed formulations is checked against literature experimental data. The proposed fracture relative permeability functions have several advantages over the existing ones. Firstly, they are explicit functions of the parameters which are known for each of simulation computational cells or easy to measure in laboratory. It is also the first model that takes gravity effects and wettability of fracture walls into consideration and individually developed for water and oil-wet systems. Furthermore, the newly developed formulations are simple, efficient and accurate. Thus, they are recommended for implementation in dual and multiple continuum commercial reservoir simulators.Résumé -Estimation analytique des perméabilités relatives de l'eau et de l'huile d'un réseau de fractures -La modélisation de l'écoulement multiphasique à travers des fractures est un sujet-clé pour mieux modéliser les écoulements au sein des réservoirs pétroliers/géothermiques, des aquifères souterrains ou lors de la séquestration de dioxyde de carbone. Cette étape est essentielle pour évaluer la production d'un réservoir, la capacité de stockage ou prédire les productions futures. Un des sujets les plus difficiles dans la modélisation des réservoirs pétroliers fracturés est de quantifier l'interaction de différents fluides lorsqu'ils s'é...

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Multiphase-flow properties of fractured porous media

Cited by 33 publications

References 13 publications

Simulating stress-dependent fluid flow in a fractured core sample using real-time X-ray CT data

Simulating stress-dependent fluid flow in a fractured core sample using real-time X-ray CT data

Quantifying fracture geometry with X-ray tomography: Technique of Iterative Local Thresholding (TILT) for 3D image segmentation

Analytical Estimation of Water-Oil Relative Permeabilities through Fractures

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