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

Solid Earth ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 657-668 ◽  
Author(s):  
Jürg Hunziker ◽  
Andrew Greenwood ◽  
Shohei Minato ◽  
Nicolás Daniel Barbosa ◽  
Eva Caspari ◽  
...  
Keyword(s):  
Waveform Inversion ◽  
Test Site ◽  
Hydrocarbon Exploration ◽  
Swiss Alps ◽  
Fracture Aperture ◽  
Full Waveform ◽  
Wide Range ◽  
Hydraulic Aperture ◽  
Vsp Data ◽  
Tube Wave

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.

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

2019 ◽  
Author(s):  
Jürg Hunziker ◽  
Andrew Greenwood ◽  
Shohei Minato ◽  
Nicolas D. Barbosa ◽  
Eva Caspari ◽  
...  
Keyword(s):  
Waveform Inversion ◽  
Test Site ◽  
Hydrocarbon Exploration ◽  
Swiss Alps ◽  
Fracture Aperture ◽  
Full Waveform ◽  
Wide Range ◽  
Hydraulic Aperture ◽  
Vsp Data ◽  
Tube Wave

Abstract. The hydraulic and mechanical characterization of fractures is crucial for a wide range of pertinent applications, such as, for example, 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.

Crosshole GPR full-waveform inversion of waveguides acting as preferential flow paths within aquifer systems

Geophysics ◽  
2012 ◽  
Vol 77 (4) ◽  
pp. H57-H62 ◽  
Author(s):  
Anja Klotzsche ◽  
Jan van der Kruk ◽  
Giovanni Meles ◽  
Harry Vereecken
Keyword(s):  
Preferential Flow ◽  
Waveform Inversion ◽  
Clay Content ◽  
Test Site ◽  
Full Waveform Inversion ◽  
Depth Range ◽  
Low Velocity ◽  
Full Waveform ◽  
Aquifer Systems ◽  
Wide Range

High-contrast layers caused by porosity or clay content changes can have a dominant effect on hydraulic processes within an aquifer. These layers can act as low-velocity waveguides for GPR waves. We used a field example from a hydrological test site in Switzerland to show that full-waveform inversion of crosshole GPR signals could image a subwavelength thickness low-velocity waveguiding layer. We exploited the full information content of the data, whereas ray-based inversion techniques are not able to image such thin waveguide layers because they only exploit the first-arrival times and first-cycle amplitudes. This low-velocity waveguide layer is caused by an increase in porosity and indicates a preferential flow path within the aquifer. The waveguide trapping causes anomalously high amplitudes and elongated wavetrains to be observed for a transmitter within the waveguide and receivers straddling the waveguide depth range. The excellent fit of amplitudes and phase between the measured and modeled data confirms its presence. This new method enables detailed aquifer characterization to accurately predict transport and flow and can be applied to a wide range of geologic, hydrological, and engineering investigations.

Reflection full waveform inversion for VSP data

2018 ◽  
Author(s):  
Lifeng Deng ◽  
Ying Shi* ◽  
Weihong Wang ◽  
Wei Zhang ◽  
Xuan Ke
Keyword(s):  
Waveform Inversion ◽  
Full Waveform Inversion ◽  
Full Waveform ◽  
Vsp Data

Quantitative conductivity and permittivity estimation using full-waveform inversion of on-ground GPR data

Geophysics ◽  
2012 ◽  
Vol 77 (6) ◽  
pp. H79-H91 ◽  
Author(s):  
Sebastian Busch ◽  
Jan van der Kruk ◽  
Jutta Bikowski ◽  
Harry Vereecken
Keyword(s):  
Quantitative Estimation ◽  
Waveform Inversion ◽  
Measured Data ◽  
Optimization Approach ◽  
Full Waveform Inversion ◽  
Near Surface ◽  
Full Waveform ◽  
Novel Approach ◽  
Wide Range ◽  
Starting Model

Conventional ray-based techniques for analyzing common-midpoint (CMP) ground-penetrating radar (GPR) data use part of the measured data and simplified approximations of the reality to return qualitative results with limited spatial resolution. Whereas these methods can give reliable values for the permittivity of the subsurface by employing only the phase information, the far-field approximations used to estimate the conductivity of the ground are not valid for near-surface on-ground GPR, such that the estimated conductivity values are not representative for the area of investigation. Full-waveform inversion overcomes these limitations by using an accurate forward modeling and inverts significant parts of the measured data to return reliable quantitative estimates of permittivity and conductivity. Here, we developed a full-waveform inversion scheme that uses a 3D frequency-domain solution of Maxwell’s equations for a horizontally layered subsurface. Although a straightforward full-waveform inversion is relatively independent of the permittivity starting model, inaccuracies in the conductivity starting model result in erroneous effective wavelet amplitudes and therefore in erroneous inversion results, because the conductivity and wavelet amplitudes are coupled. Therefore, the permittivity and conductivity are updated together with the phase and the amplitude of the source wavelet with a gradient-free optimization approach. This novel full-waveform inversion is applied to synthetic and measured CMP data. In the case of synthetic single layered and waveguide data, where the starting model differs significantly from the true model parameter, we were able to reconstruct the obtained model properties and the effective source wavelet. For measured waveguide data, different starting values returned the same wavelet and quantitative permittivities and conductivities. This novel approach enables the quantitative estimation of permittivity and conductivity for the same sensing volume and enables an improved characterization for a wide range of applications.

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