Full waveform inversion in crosshole environment
Full waveform inversion, Crosswell tomography, seismic tomography
Crosswell seismic tomography is one of the classic seismic inversion techniques, often applied in exploration and exploitation of mineral resources, monitoring of hydrocarbon reservoirs and imaging of complex geological structures. Because its source has a high frequency, this technique allows a better resolution than other techniques for shallow
and reservoir level investigations. In the tomographic formulation, when dealing with geological structures that present subvertical dips, this technique becomes unfeasible because of the low illumination. In general, the tomograms obtained are not reliable because they contain artifacts that do not correspond to the actual structures. In an attempt to solve this problem, an adaptation of the FWI technique to the crosswell array was carried out through a finitedifference acoustic modeling. This makes it possible to use not only the traveltimes of the wave phases, as it is done in the case of the ray tracing approach, but all the waveform information. The results obtained so far show that FWI significantly improves the resolution of the tomograms within the angular coverage region. In addition, in the region outside the angular coverage, the tomograms show better correlation with the actual structures, evidencing that the problem of lack of illumination can be attenuated.