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

Forward modeling plays an important role in structural trap exploration bec ause 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 t otal estimated reserves, suggesting that there are undiscovered lithologic traps. According to the stratum properties revealed by borehole surveying a nd exploration seismograms, we have constructed the models of deposit sand body traps and conducted a complex seismic wave modeling study using the fi nite element method. Out models contain scattering bodies. The trap media is considered viscous- elastic and finite element equations are derived with artificial boundary t erms. The absorbing effect of the artificial boundary terms we obtained is fairly good. The source is simulated by concentrated forces or explosive so urces. We obtain the common source/receiver record profiles by putting seco ndary sources directly on the interface nodes. Direct waves and surface wav es of single-shot seismograms can be removed with Huygen's principle. We al so 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 corres ponding records have been analyzed and the characteristics have been extrac ted. The method will provide an analytical tool for exploring lithologic tr aps effectively. (C) 2000 Elsevier Science B.V. All rights reserved.