Autoren:	Kling, Tobias Huo, Da Schwarz, Jens-Oliver Enzmann, Frieder Benson, Sally Blum, Philipp
Titel:	Simulating stress-dependent fluid flow in a fractured core sample using real-time X-ray CT data
Online-Publikationsdatum:	2-Aug-2016
Erscheinungsdatum:	2016
Sprache des Dokuments:	Englisch
Zusammenfassung/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 mm3. 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 CTmat (1862.6 HU) depicting the matrix material represents the most sensitive input parameter of the simulations. Small variations of CTmat 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.
DDC-Sachgruppe:	550 Geowissenschaften 550 Earth sciences
Veröffentlichende Institution:	Johannes Gutenberg-Universität Mainz
Organisationseinheit:	FB 09 Chemie, Pharmazie u. Geowissensch.
Veröffentlichungsort:	Mainz
ROR:	https://ror.org/023b0x485
DOI:	http://doi.org/10.25358/openscience-685
URN:	urn:nbn:de:hebis:77-publ-545061
Version:	Published version
Publikationstyp:	Zeitschriftenaufsatz
Nutzungsrechte:	CC BY
Informationen zu den Nutzungsrechten:	https://creativecommons.org/licenses/by/3.0/
Zeitschrift:	Solid earth 7 4
Seitenzahl oder Artikelnummer:	1109 1124
Verlag:	Copernicus Publ.
Verlagsort:	Göttingen
Erscheinungsdatum:	2016
ISSN:	1869-9529 1869-9510
URL der Originalveröffentlichung:	http://dx.doi.org/10.5194/se-7-1109-2016
DOI der Originalveröffentlichung:	10.5194/se-7-1109-2016
Enthalten in den Sammlungen:	JGU-Publikationen