2-D finite element modeling for seismic wave response in media with sand bodies

Abstract

Forward modeling plays an important role in structural trap exploration because of its usefulness in identifying seismic wave characteristics. Structural traps have been discovered in the Dongpu depression of Zhongyuan Oil Field of China. However, its proved reserves still fall far short of total estimated reserves, suggesting that there are undiscovered lithologic traps. According to the stratum properties revealed by borehole surveying and exploration seismograms, we have constructed the models of deposit sand body traps and conducted a complex seismic wave modeling study using the finite element method. Our models contain scattering bodies. The trap media is considered viscous–elastic and finite element equations are derived with artificial boundary terms. The absorbing effect of the artificial boundary terms we obtained is fairly good. The source is simulated by concentrated forces or explosive sources. We obtain the common source/receiver record profiles by putting secondary sources directly on the interface nodes. Direct waves and surface waves of single-shot seismograms can be removed with Huygen's principle. We also put the filter of instrument response into the theoretical seismograms. In the paper, we have designed several models of sand bodies, and obtained their realistic seismic profiles with the finite element method. The corresponding records have been analyzed and the characteristics have been extracted. The method will provide an analytical tool for exploring lithologic traps effectively.