19. Estimation of Local Anisotropy Using Polarisations and Travel Times from the Oseberg 3DVSP

摘要: Observations of polarisations and slownesses at downhole receivers in walka- way or multioffset VSP experiments can principle be inverted to give the anisotropic seismic velocity earth vicinity receiver array. In practice, such inver- sions have been only rarely reported, possibly due a general lack confidence po- larisation measurements. We apply an inversion direct P-wave arrivals from 3D dataset acquired Oseberg field Norwegian North Sea. The large size this ensures that result is more stable than those comparable inversions applied standard 2D datasets. Comparison with established, but restricted, method surface showed discrepancy. Further investigation revealed acquisition-related co- herent noise on estimated slownesses; there no corresponding effect polarisation because each shot treated independently. therefore prefer case.