Chapter 7: Multiple-scale-porosity Wavelet Simulation Using GPR Tomography and Hydrogeophysical Analogs
Erwan Gloaguen, Bernard Giroux, Denis Marcotte, Camille Dubreuil-Boisclair, Patrick Tremblay-Simard, 2010. "Multiple-scale-porosity Wavelet Simulation Using GPR Tomography and Hydrogeophysical Analogs", Advances in Near-surface Seismology and Ground-penetrating Radar, Richard D. Miller, John H. Bradford, Klaus Holliger
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A novel approach can be used to simulate porosity fields constrained by borehole-radar tomography images. The cornerstone of the method is statistical analysis of the approximation wavelet coefficients of a petrophysical analog scenario. The method is tested with a 2D synthetic porosity field generated from a digital picture of a real sand deposit. The porosity field is translated into electrical properties and a crosshole tomography synthetic survey is built using a finite-difference modeling algorithm. Hereafter, this synthetic survey is considered as the measured one. In parallel, an analog deposit is created based on geologic knowledge of the area under study. The analog porosity field is converted into electrical property fields using the same equation. A synthetic ground-penetrating-radar (GPR) tomography also is computed from the latter. Then, wavelet decomposition of both measured and analog tomography and porosity analog fields is calculated. Based on the assumption that geophysical data carry essentially large-scale information about the geology, statistical analysis of the approximation wavelet coefficients of each variable is carried out. From measured tomographic approximation coefficients and cross statistics evaluated on the analogs, approximation of the real porosity field is inferred. Finally, based on the statistical relationships between wavelet coefficients across the different scales, all porosity wavelet-detail coefficients are simulated using a standard geostatistical cosimulation algorithm. The wavelet coefficients then are back-transformed in the porosity space. The final simulated porosity fields contain the large wavelengths of the measured radar tomographic images and the texture of the analog porosity field.
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Near-surface seismology and ground-penetrating radar (GPR) have enjoyed success and increasing popularity among a wide range of geophysicists, engineers, and hydrologists since their emergence in the latter half of the twentieth century. With the common ground shared by near-surface seismology and GPR, their significant upside potential, and rapid developments in the methods, a book bringing together the most current trends in research and applications of both is fitting and timely. Conceptually, near-surface seismology and GPR are remarkably similar, and they share a range of attributes and compatibilities that provides opportunities to integrate processing and interpretation workflows, which makes them a perfect pair to share pages in a book.
With growth in numbers and professional emphasis have come sections, focus groups, and even professional societies specifically promoting near-surface geophysics. The emergence of near-surface geophysics groups, beginning in the late 1990s and extending into the early twenty-first century, has fueled a diversity of opportunities for professional collaborations. A range of workshops and shared publications has been the fruit of collaborative efforts. The near-surface community continues to extend and develop methods and approaches necessary to satisfy increasing demands in some of the socioeconomically pertinent disciplines such as civil and environmental engineering and hydrology. This book represents the first formal cooperative effort undertaken by the near-surface communities of the Society of Exploration Geophysicists, the American Geophysical Union, and the Environmental and Engineering Geophysical Society.