Tomographic joint inversion of first arrivals in a real case fromSaudi Arabia

Abstract

A B S T R A C TA joint inversion of both first and refracted arrivals is applied on a seismic line, acquired onshore, in order to obtain a well-resolved velocity field for the computation of static corrections. The use of different arrivals in the inversion involves exploiting the information derived from the different raypaths associated with each wave type, thus enhancing the reliability of the inversion. The data was gathered by Saudi Aramco in an area of the Arabian Peninsula characterized by strong lateral variations, both in topography and shallow velocity, and where therefore a well-defined near-surface velocity field is important. In addition to velocity, the depth distribution of the quality factor Q is computed from the tomographic inversion of the seismic-signal frequency shift. Thus, the Q-factor field is used to perform an inverse Q-data filtering and improve the resolution of the final stacked section.

Attenuation tomography: An application to gas‐hydrate and free‐gas detection

“…Furthermore, on land, surface heterogeneities may change the frequency content of the first arrivals laterally, so that we may obtain only a relative variation of the attenuation with respect to the shallowest layer (e.g. Böhm et al 2006).…”

“…When we use a single reference spectrum for the analysis, w2 is set to be coincident with the trace number of the data set, or better, to be smaller than the trace number, so as to follow eventual lateral variations of the shallowest layer. In an onshore case with known topographical and geological lateral variations, Böhm et al (2006) estimated the reference power spectrum by averaging the power spectra relative to the nearest first arrivals, (excluding the zero-offset arrivals), and showed the effect of different averaging window widths.…”

A field assessment of site‐specific correlations between hydraulic and geophysical parameters

“…Diving waves propagate downwards from a ground level along a curved raypath. The depth of the rays depends on the velocity gradient within the shallow part of the subsoil (Stefani 1995;Böhm et al 2006). As a starting model for the inversion we used a homogeneous velocity field and the raypaths were represented by arcs.…”

Yardsticks for industrial tomography

“…Multi-component recording allows the separation of P, S and converted waves. Visco-elastic inversion can double the parameter number, adding the shear velocity Vs and quality factor Qs to their compressional counterparts Vp and Qp (Liao and McMechan 1997;Quan and Harris 1997;Zhou et al 1997;Wang et al 1998;Brzostowski and McMechan 2001;Böhm et al 2006).…”