Looking into the Near Surface with More Data and Multiple Joint Imaging Technologies

Abstract:

While exploration geophysicists are making tremendous efforts to image the deep subsurface for hydrocarbon resources, the complex near surface structures often impose significant challenges. Unlike the subsurface, the near surface structures vary from region to region. Thus, it is difficult to develop any benchmark model that represents common issues worldwide. During past 20 years, near surface imaging technologies have been advanced from refraction traveltime analysis and inversion to waveform inversion. Immediate benefit is to resolve any complex velocity structure associated with low velocity hidden layers if such waveform inversion is properly handled. However, inverting seismic waveform often suffers from cycle-skipping due to poor starting model or missing of low frequency data. Jointly inverting traveltime, waveform envelope and waveform data seems stabilizing the solutions. With more data utilized for the near surface imaging, we are also able to infer anisotropic parameters, attenuation factors, density, and both Vp and Vs. Since the cross-gradient approach was introduced in 2005, the simultaneous inversion of multiple types of geophysical data has also been applied in the near surface imaging. That includes joint seismic, gravity and EM inversion for mapping seismic velocity, density, and resistivity into a near surface structure with consistent geology. I demonstrate the changes of the near surface structural images due to the progress of the imaging technology development and the transition to much more data included with five real data examples.