Chapter 23: Estimation of Chalk Heterogeneity from Stochastic Modeling Conditioned by Crosshole GPR Traveltimes and Log Data
Lars Nielsen, Majken C. Looms, Thomas M. Hansen, Knud S. Cordua, Lars Stemmerik, 2010. "Estimation of Chalk Heterogeneity from Stochastic Modeling Conditioned by Crosshole GPR Traveltimes and Log Data", Advances in Near-surface Seismology and Ground-penetrating Radar, Richard D. Miller, John H. Bradford, Klaus Holliger
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Rocks from the Chalk Group host important reservoirs of groundwater onshore Denmark and oil and gas in the North Sea. Fine-scale heterogeneity of rocks from the Chalk Group is investigated by stochastic modeling conditioned by first-arrival crosshole GPR traveltimes and lithology data from boreholes. The water-saturated carbonate-dominated rocks contain sharp contrasts among highly porous low-velocity carbonate, thin intercalations of flint, and hardened low-porosity carbonate of higher velocity. The stochastic simulation algorithm can model the contrasting lithologies effectively. It is found that bimodal distributions produce geologically plausible representations of the subsurface. Moreover, the variety of tested stochastic models that honors the specified data uncertainties and prior information provide a good overview of possible subsurface scenarios that the combined data set allows for. Results motivate future GPR-based tracer tests and time-lapse studies for generation of new knowledge of the dynamics of Chalk Group fluid flow.
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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.