1D Anisotropic Velocity Model Inversion from Multi-offset VSP Data Sets (Conventional Array and Optical Cable)

Optical seismic acquisition with distributed vibration sensing has been recently proposed to improve seismic acquisition efficiency (Hartog et al. 2013). An experimental multi-offset VSP data set has been acquired with both conventional and optical technologies in a 620-m-deep cased vertical well (Frignet and Hartog 2014). The 1D isotropic ray trace modelling times cannot be matched with picked transit times. It is necessary to introduce some VTI anisotropy to reconcile modelled and measured times at all offsets. Both conventional and optical VSP times were satisfactorily modelled with a 1D anisotropic model. Conventional multi-offset VSPs are not often acquired. In addition to the successful Thomsen anisotropic parameters inversion, an optical VSP acquisition is an order of magnitude faster than conventional acquisition. Therefore, multi-offset optical VSP could be routinely acquired in less time than conventional zero-offset VSP. Multi-offset VSP is a cost-effective technology for investigating velocity anisotropy in horizontally layered environments