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Bayesian full-waveform inversion of tube waves to estimate fracture aperture and compliance

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Hunziker Jürg, Greenwood Andrew, Minato Shohei, Barbosa Nicolás Daniel, Caspari Eva, Holliger Klaus,
Project Exploration and characterization of deep underground reservoirs
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Original article (peer-reviewed)

Journal Solid Earth
Volume (Issue) 11(2)
Page(s) 657 - 668
Title of proceedings Solid Earth
DOI 10.5194/se-11-657-2020

Open Access

URL http://doi.org/10.5194/se-11-657-2020
Type of Open Access Publisher (Gold Open Access)

Abstract

Abstract. The hydraulic and mechanical characterization of fractures is crucial for a wide range of pertinent applications, such as geothermal energy production, hydrocarbon exploration, CO2 sequestration, and nuclear waste disposal. Direct hydraulic and mechanical testing of individual fractures along boreholes does, however, tend to be slow and cumbersome. To alleviate this problem, we propose to estimate the effective hydraulic aperture and the mechanical compliance of isolated fractures intersecting a borehole through a Bayesian Markov chain Monte Carlo (MCMC) inversion of full-waveform tube-wave data recorded in a vertical seismic profiling (VSP) setting. The solution of the corresponding forward problem is based on a recently developed semi-analytical solution. This inversion approach has been tested for and verified on a wide range of synthetic scenarios. Here, we present the results of its application to observed hydrophone VSP data acquired along a borehole in the underground Grimsel Test Site in the central Swiss Alps. While the results are consistent with the corresponding evidence from televiewer data and exemplarily illustrate the advantages of using a computationally expensive stochastic, instead of a deterministic inversion approach, they also reveal the inherent limitation of the underlying semi-analytical forward solver.
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