Numerical modeling of 3D zero-offset laboratory data by a discretized Kirchhoff integral method

Abstract

International audienceAccurate simulation of seismic wave propagation in complex geologic structures is of particular interest nowadays. However, difficulties arise for complex geologic structures with great and rapid structural changes, due, for instance, to the presence of shadow zones, head waves, diffractions and/or edge effects. Different methods have thus been developed and are typically tested on synthetic configurations against analytical solutions for simple canonical problems, reference methods, or via direct comparison with real data acquired in situ. Such approaches have limitations, especially if the propagation occurs in a complex environment with strong-contrast reflectors and surface irregularities because it can be difficult to determine the method that gives the best approximation of the "real" solution or to interpret the results obtained without an a priori knowledge of the geologic environment. An alternative approach for seismics consists in comparing the synthetic data with data obtained in laboratory experiments. In contrast to in situ experiments, high-quality data are collected under controlled conditions for a known configuration. In contrast with numerical experiments, laboratory data possess many of the characteristics of field data because real waves propagate through models with no numerical approximations. Our main purpose was to test the approach of using laboratory data as reference data for benchmarking 3D numerical methods and techniques using the setup that we have designed for this study. We performed laboratory-scaled measurements of zero-offset reflection of broadband pulses from a strong topographic environment immersed in a water tank. We compared these measurements with numerical data simulated by means of a discretized Kirchhoff integral method. The comparisons of synthetic and laboratory data indicated a good quantitative fit in terms of time arrivals and acceptable fit in amplitudes. Thus, the first step of the approach was successfully applied

Seismic surveying and imaging at the laboratory scale: A framework to cross-validate experiments and simulations for a salt-body environment

“…This transducer has a dominant frequency of 500 kHz (i.e., 25 Hz at seismic scale) and a broad-beam radiation pattern. Because the width of the main lobe is 35° at -3 dB, this transducer has a large area of illumination, leading to a complex 3D wavefield (Tantsereva et al, 2014a, 2014b, Solymosi et al, 2018. In the offset configuration, an omnidirectional Teledyne Reson® hydrophone was used as the receiver, which has a constant sensitivity for the frequency range of interest.…”

“…In this context, after having experienced a drop in laboratory experimentation related papers for two decades, laboratory experiments are now re-considered as a tool to understand real field data and purely numerical datasets as well, to facilitate the testing of new ideas (Becker et al, 2018), to investigate the physics underlying wave propagation that is not sufficiently understood (Cooper et al, 2010, Stewart et al, 2012, Ekanem et al, 2013, Xu et al, 2016, Chang et al, 2017, as well as to test numerical algorithms used for data processing and imaging (Campman et al, 2005, Chai et al, 2015. Recently, small-scale modeling approaches have been developed as tools to test numerical modeling and seismic-imaging methods in the context of onshore and offshore seismics (Bretaudeau et al, 2011, 2013, Favretto-Cristini et al, 2014, Tantsereva et al, 2014a,b, Solymosi et al, 2018. In particular, Tantsereva et al (2014a) have evaluated the ability of a 3D discretized Kirchhoff integral method (DKIM) to accurately simulate complex diffractions using a zero-offset laboratory data set, measured for a reduced-scale model with strong topography and immersed in a water tank.…”

“…Recently, small-scale modeling approaches have been developed as tools to test numerical modeling and seismic-imaging methods in the context of onshore and offshore seismics (Bretaudeau et al, 2011, 2013, Favretto-Cristini et al, 2014, Tantsereva et al, 2014a,b, Solymosi et al, 2018. In particular, Tantsereva et al (2014a) have evaluated the ability of a 3D discretized Kirchhoff integral method (DKIM) to accurately simulate complex diffractions using a zero-offset laboratory data set, measured for a reduced-scale model with strong topography and immersed in a water tank. Comparisons of numerical and laboratory data sets have shown that the DKIM could correctly reproduce the wavefield, except in the vicinity of shadow zones created by the interaction on the edges of the topographic structures.…”

“…It is obvious that the size of the sources and receivers used in the laboratory experiments cannot be compared to the sources/receivers used on the field. Nevertheless, laboratory sensors with a large area of illumination to emphasize the different wave phenomena observed in field experiments (e.g., multiple diffractions, wave focusing/defocusing) are available nowadays (Tantsereva et al, 2014a). Moreover, thanks to a broad range of metals, resins, and composite materials, one can often find materials with somewhat identical density and P-and Swave velocities.…”

“…Far from being exhaustive, this list may, however, be a useful starting point for similar studies combining laboratory experiments and numerical simulations. For the sake of illustration we rely on a much more complex case study that is also much more realistic from a geological viewpoint than the configurations considered in our previous works (Tantsereva et al, 2014a, Solymosi et al, 2018 or configurations considered in other works (e.g. Cooper et al, 2010, Stewart et al, 2012, Chang et al, 2017, Pageot et al, 2017, namely a complex-shaped salt body buried in sedimentary layers with curved surfaces.…”