Investigating the use of 3D full-waveform inversion to characterise the host rock at a geological disposal site
File(s)
Published version
OA Location
Author(s)
Bentham, Hannah
Morgan, JV
Angus, Douglas
Type
Journal Article
Abstract
The U.K. government has a policy to dispose of higher activity radioactive waste in a geological disposal facility (GDF), which will have multiple protective barriers to keep the waste isolated and to ensure no harmful quantities of radioactivity are able to reach the surface. Currently no specific GDF site in the United Kingdom has been chosen but, once it has, the site is likely to be investigated using seismic methods. In this study, we explore whether 3-D full-waveform inversion (FWI) of seismic data can be used to map changes in physical properties caused by the construction of the site, specifically tunnel-induced fracturing. We have built a synthetic model for a GDF located in granite at 1000 m depth below the surface, since granite is one of the candidate host rocks due to its high strength and low permeability and the GDF could be located at such a depth. We use an effective medium model to predict changes in P-wave velocity associated with tunnel-induced fracturing, within the spatial limits of an excavated disturbed zone (EdZ), modelled here as an increase in fracture density around the tunnel. We then generate synthetic seismic data using a number of different experimental geometries to investigate how they affect the performance of FWI in recovering subsurface P-wave velocity structure. We find that the location and velocity of the EdZ are recovered well, especially when data recorded on tunnel receivers are included in the inversion. Our findings show that 3-D FWI could be a useful tool for characterizing the subsurface and changes in fracture properties caused during construction, and make a suite of suggestions on how to proceed once a potential GDF site has been identified and the geological setting is known.
Date Issued
2018-12-01
Date Acceptance
2018-09-05
Citation
Geophysical Journal International, 2018, 215 (3), pp.2035-2046
ISSN
0956-540X
Publisher
Oxford University Press (OUP)
Start Page
2035
End Page
2046
Journal / Book Title
Geophysical Journal International
Volume
215
Issue
3
Copyright Statement
The Author(s) 2018. Published by Oxford University Press on behalf of The Royal Astronomical Society. This is an Open Access
article distributed under the terms of the Creative Commons Attribution License (
http://creativecommons.org/licenses/by/4.0/
), which
permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
article distributed under the terms of the Creative Commons Attribution License (
http://creativecommons.org/licenses/by/4.0/
), which
permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
Sponsor
BG International Limited
Sub Salt Solutions
Grant Number
4100005341
EACPR_P73721
Subjects
0404 Geophysics
0403 Geology
0909 Geomatic Engineering
Geochemistry & Geophysics
Publication Status
Published
Date Publish Online
2018-09-18