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Collaborating Authors
Giroux, Bernard
Understanding the effects of permafrost degradation through a multi-physics approach
Vosoughi, Ehsan (Institut National de la Recherche Scientifique (INRS)) | Giroux, Bernard (Institut National de la Recherche Scientifique (INRS)) | Duchesne, Mathieu J. (Geological Survey of Canada) | Dupuis, J. Christian (Universit Laval)
Permafrost is a multiphase porous media that can host matter in all three states (solid, liquid, and gas). The equilibrium between the states of matter within the pore space is largely driven by salinity, pressure, and temperature. The complex interactions between the different thermodynamic processes can lead to a complex pore system that is altered at each subsequent thaw and freeze cycle. The dynamic changes imposed on this porous media alter the mechanical and electrical properties of the samples. These changes can thus be quantified and monitored using ultrasonic and electrical resistivity measurements. The experimental results presented in this work document the impacts of a thawing event on unconsolidated quartz sand samples that were partially saturated with a brine solution. The electrical resistivity and ultrasonic data were acquired simultaneously throughout the experiment and the spatiotemporal changes within the solid matrix were captured by time-lapse X-ray Computed Tomography. A total of 39 different samples were investigated. The two independent variables chosen for this study were the grain size and the salinity of the brines. The results show a clear transition in electrical and elastic properties as the material in the pore space transitions between two different states. Further results show that these transitions are the result of the alteration of the pore network itself. Also, the study of P-wave velocity, ice fraction, and X-ray computed tomography of two different types of ice that coexist within the pore network is documented. Given the distinct impact of two different types of ice on this cryogenic porous media, it is imperative to thoroughly comprehend the existence of different ice types before undertaking the electro-elastic investigation of permafrost.
- Research Report > New Finding (0.86)
- Research Report > Experimental Study (0.54)
- Geophysics > Seismic Surveying (1.00)
- Geophysics > Borehole Geophysics (1.00)
- Energy > Oil & Gas > Upstream (1.00)
- Materials > Chemicals > Commodity Chemicals > Petrochemicals (0.92)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Open hole/cased hole log analysis (1.00)
- Data Science & Engineering Analytics > Information Management and Systems > Artificial intelligence (0.92)
Robust quantitative estimation of the seismic attenuation from shallow geotechnical borehole VSP data
Nasr, Maher (Institut National de la Recherche Scientifique) | Giroux, Bernard (Institut National de la Recherche Scientifique) | Fabien-Ouellet, Gabriel (รcole Polytechnique Montrรฉal) | Vergniault, Christophe (รlectricitรฉ De France) | Simon, Cyril (รlectricitรฉ De France)
ABSTRACT Estimating seismic attenuation from shallow geotechnical borehole surveys can be a delicate task. Measured data are often collected within the source near-field domain and the classic inverse-distance correction of the geometric spreading (GS) is inappropriate at this scale. We develop a novel approach based on a 3D full-waveform modeling to substitute the inverse-distance correction. It consists of scaling the picked amplitudes using their counterparts obtained from an elastic simulation carried out under conditions mimicking the data acquisition. The seismic attenuation may be inferred from the corrected amplitudes using either a piecewise regression or a ray-based inversion. Numerical experiments involving P- and S-wave synthetic data indicate that our correction better compensates for the GS effect than the inverse-distance correction. For a synthetic example with 5% noise, the Q-factor values derived from amplitude corrected via the proposed approach have a relative error of approximately 10% compared with 40% for the traditional correction. We investigate the effect of the velocity and density uncertainty upon the calculated correction terms and show that our approach is unbiased and stable. Finally, the robustness of our workflow is assessed on a real case study involving a P-wave data set acquired in a geotechnical borehole.
- North America > United States (0.68)
- North America > Canada > Quebec (0.28)
- Geology > Geological Subdiscipline (0.67)
- Geology > Structural Geology > Tectonics > Plate Tectonics > Earthquake (0.47)
- Geology > Rock Type > Sedimentary Rock (0.46)
Robust quantitative estimation of the seismic attenuation from shallow geotechnical borehole VSP data
Nasr, Maher (Institut National de la Recherche Scientifique) | Giroux, Bernard (Institut National de la Recherche Scientifique) | Fabien-Ouelle, Gabriel (cole Polytechnique Montral) | Vergniault, Christophe (lectricit De France) | Simon, Cyril (lectricit De France)
Estimating the seismic attenuation from shallow geotechnical borehole surveys can be a delicate task. Measured data are often collected within the source near-field domain and the classic inverse-distance correction of the geometrical spreading is inappropriate at this scale. We propose a novel approach based on a 3D full waveform modeling to substitute the inverse-distance correction. It consists in scaling the picked amplitudes using their counterparts obtained from an elastic simulation carried out under conditions mimicking the data acquisition. The seismic attenuation may be inferred from the corrected amplitudes using either a piecewise regression or a ray-based inversion. Numerical experiments involving P- and S-wave synthetic data show that the proposed correction better compensates for the geometrical spreading effect than the inverse-distance correction. For a synthetic example with 5% noise, the Q-factor values derived from amplitude corrected via the proposed approach have a relative error of about 10%, compared to 40% for the traditional correction. We investigate the effect of the velocity and density uncertainty upon the calculated correction terms and show that our approach is unbiased and stable. Finally, the robustness of the proposed workflow is assessed on a real case study involving a P-wave dataset acquired in a geotechnical borehole.
- North America > United States (0.93)
- North America > Canada > Quebec (0.28)
- Geology > Geological Subdiscipline (0.67)
- Geology > Structural Geology > Tectonics > Plate Tectonics > Earthquake (0.46)
- Geology > Rock Type > Sedimentary Rock (0.46)
ABSTRACT As seismic data can contain information over a large spatial area and are sensitive to changes in the properties of the subsurface, seismic imaging has become the standard geophysical monitoring method for many applications such as carbon capture and storage and reservoir monitoring. The availability of practical tools such as full-waveform inversion (FWI) makes time-lapse seismic FWI a promising method for monitoring subsurface changes. However, FWI is a highly ill-posed problem that can generate artifacts. Because the changes in the earthโs properties are typically small in terms of magnitude and spatial extent, discriminating the true time-lapse signature from noise can be challenging. Different strategies have been proposed to address these difficulties. In this study, we propose a weighted-average (WA) inversion to better control the effects of artifacts and differentiate them from the true 4D changes. We further compare five related strategies with synthetic tests on clean and noisy data. The effects of seawater velocity variation on different strategies also are studied as one of the main sources of nonrepeatability. We tested different strategies of time-lapse FWI (TL-FWI) using the Marmousi and the SEG Advanced Modeling time-lapse models. The results indicate that the WA method can provide the best compromise between accuracy and computation time. This method also provides a range of possible answers of other TL-FWI strategies.
- North America > Canada (0.28)
- North America > United States (0.28)
- North America > United States > Gulf of Mexico > Central GOM > East Gulf Coast Tertiary Basin > Green Canyon > Block 205 > Genesis Field > Neb Formation (0.99)
- Europe > Norway > North Sea > Central North Sea > Central Graben > Block 2/8 > Valhall Field > Tor Formation (0.99)
- Europe > Norway > North Sea > Central North Sea > Central Graben > Block 2/8 > Valhall Field > Hod Formation (0.99)
- (2 more...)
- Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)
- Reservoir Description and Dynamics > Reservoir Characterization > Four-dimensional and four-component seismic (1.00)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Seismic (four dimensional) monitoring (1.00)
We present a new single-level method for microseismic event detection and first-break picking. The method is added to the arsenal of window-based techniques that are available to deal with multicomponent data. It was conceived to be less time consuming and easy to parameterize. The proposed method estimates the linear polarization level through a new rectilinearity function that analyzes the signal polarization using the correlation matrix. This innovative approach allows users to establish a meaningful set of metrics for the interpretation of rectilinearity. These metrics facilitate the choice of thresholds used to distinguish seismic events from ambient noise. The performance of this novel time-domain approach is presented for synthetic and real microseismic data. Results show that the proposed method can be an efficient alternative to more traditional schemes.
- Research Report > Experimental Study (0.48)
- Overview > Innovation (0.34)
We present preliminary results of simultaneous laboratory experiments to measure the impact of permafrost thawing on geophysical properties of partially-saturated frozen sediment samples. Coincident acoustic, electrical resistivity and X-ray computed tomography measurements are conducted on synthetic permafrost samples to determine the behavior of the fluid and the matrix during thawing. Results suggest that attenuation for sample with the higher salinity increased by 15 dB in comparison to the lower salinity sample. Also, according to electrical resistivity, temperature variation has a greater influence on the low salinity sample. CT images showed that permafrost degradation reduced the cohesiveness of the sediments. This increases attenuation and porosity. Finally, fine-scale and complex interactions between the matrix and saline fluids affecting effective porosity, are suspected during permafrost thaw. However, this requires further analyses before it can be confirmed.
- Research Report > New Finding (0.48)
- Research Report > Experimental Study (0.48)
- Geophysics > Seismic Surveying (0.97)
- Geophysics > Borehole Geophysics (0.60)
ABSTRACT Polarization filters (PFs) are widely used for denoising seismic data. These filters are applied in the fields of seismology, microseismic monitoring, vertical seismic profiling, and subsurface imaging. They are primarily useful to suppress ground roll in seismic reflection data and enhance P- and S-wave arrivals. Traditional implementations of PFs involved the analysis of the covariance matrix or the singular value decomposition (SVD) of a 3C seismogram matrix. The linear polarization level, known as rectilinearity, is expressed as a function of the covariance matrix eigenvalues or by the data matrix singular values. Wavefield records that are linearly polarized are amplified, whereas others are attenuated. Besides the described implementations, we have developed a new time-domain PF based on the analysis of the seismic data correlation matrix. The principal idea is to extend the notion of the correlation coefficient in 3D space. This new filter avoids the need for diagonalization of the covariance matrix or SVD of data matrix, which are often time-consuming. The new implementation facilitates the choice of the rectilinearity threshold: We determine that linear polarization in three dimensions can be represented as three classic 2D correlations. A good linear polarization is detected when a high linear correlation between the three seismogram components is mutually observed. The tuning parameters of the new filter are the length of the time window, the filter order, and the rectilinearity threshold. Tests using synthetic seismograms indicate that optimal results are reached with a filter order that spans between 2 and 4, a rectilinearity threshold between 0.3 and 0.7, and a window length that is equivalent to one to three times the period of the signal wavelet. Compared with covariance-based filters, the new filter can enhance the signal-to-noise ratio by 6โ20ย dB and reduces computational costs by 25%.
- Geophysics > Seismic Surveying > Seismic Processing (1.00)
- Geophysics > Seismic Surveying > Borehole Seismic Surveying > Vertical Seismic Profile (VSP) (1.00)
- Geophysics > Seismic Surveying > Passive Seismic Surveying > Microseismic Surveying (0.68)
- Geophysics > Seismic Surveying > Passive Seismic Surveying > Earthquake Seismology (0.66)
ABSTRACT We present an optimized method to calculate traveltimes for seismic inversion. It is a hybrid version of the shortest path approach. The main improvements consist in computing traveltimes using the seismic ray paths and using temporary secondary nodes in vicinity of the source. The proposed method is done following two sequential steps. In the first step, traveltimes are computed for all nodes using the modified shortest path method. Ray paths are then traced back for all source-receiver couples and traveltimes for each receiver are updated using nodes along the ray path. Tests have shown that this approach can improve the accuracy by an order of magnitude and save up to a third of the computation time when compared to the standard shortest path algorithm. Presentation Date: Thursday, October 18, 2018 Start Time: 8:30:00 AM Location: 211A (Anaheim Convention Center) Presentation Type: Oral
ABSTRACT In this paper, we study the performance of joint time-lapse inversion of borehole ERT and magnetometric resistivity data in the context of quantitative monitoring of CO storage. We have considered the injection of CO in a thick sandstone aquifer at a depth of 75 m. The CO plume extension is modeled as a resistive zone with increased lateral extensions. Inversion results show that joint MMR and ERT data is a more robust tool to follow the evolution of CO plume propagation than the separate inversions. Presentation Date: Monday, September 25, 2017 Start Time: 4:45 PM Location: 362A Presentation Type: ORAL
- Geophysics > Electromagnetic Surveying (1.00)
- Geophysics > Magnetic Surveying (0.87)
- Geophysics > Borehole Geophysics (0.85)
- Facilities Design, Construction and Operation > Unconventional Production Facilities > CO2 capture and management (0.84)
- Reservoir Description and Dynamics > Reservoir Characterization (0.71)
- Reservoir Description and Dynamics > Formation Evaluation & Management > Open hole/cased hole log analysis (0.70)
A stochastic L-BFGS approach for full-waveform inversion
Fabien-Ouellet, Gabriel (INRS) | Gloaguen, Erwan (INRS) | Giroux, Bernard (INRS)
ABSTRACT Speeding-up convergence rates and reducing the computational burden of Full Waveform Inversion (FWI) is increasingly important as we move toward large-scale 3D multi-parameter inversion. To this end, second-order optimization algorithms like L-BFGS or the truncated Newton method allow a much faster convergence rate at minimal computational costs. In the same fashion, stochastic source subsampling approaches have been shown to reduce the computational cost of FWI. In this study, we propose to combine these two strategies and present how the L-BFGS algorithm can be used along with the stochastic source subsampling strategy, or what we call the stochastic L-BFGS algorithm. Presentation Date: Tuesday, September 26, 2017 Start Time: 2:40 PM Location: Exhibit Hall C, E-P Station 3 Presentation Type: EPOSTER
- Information Technology > Artificial Intelligence > Representation & Reasoning > Mathematical & Statistical Methods (0.38)
- Information Technology > Artificial Intelligence > Representation & Reasoning > Optimization (0.34)
- Information Technology > Artificial Intelligence > Machine Learning > Statistical Learning (0.32)