An experimental nodal OBS acquisition from the Thunder Horse Field, Gulf of Mexico

Ray, Amal; Noltem, Bertram; Herron, Don

doi:10.1190/1.1901395

Cited by 5 publications

(1 citation statement)

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“…Modern acquisition systems make use of 4C sensors consisting of a multicomponent geophone and a hydrophone, to record the elastic wavefield in the solid seabed and the acoustic wavefield in the water just above the seabed. They are usually connected to each other by, and are housed within, a so-called ocean-bottom cable (OBC), which transmits data to a recording system on a boat using wired telemetry, while a second boat fires a marine source around and over the sensors (Berg et al, 1994;Amal et al, 2005). Alternatively, remotely operated vehicles can be used to deploy individual sensor nodes (ocean-bottom node, OBN) on the seafloor allowing more flexible acquisition geometries (Ronen et al, 2003;Granger et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Elastic imaging with exact wavefield extrapolation for application to ocean-bottom 4C seismic data

Ravasi

Curtis

2013

GEOPHYSICS

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A central component of imaging methods is receiver-side wavefield backpropagation or extrapolation in which the wavefield from a physical source scattered at any point in the subsurface is estimated from data recorded by receivers located near or at the Earth's surface. Elastic reverse-time migration usually accomplishes wavefield extrapolation by simultaneous reversed-time 'injection' of the particle displacements (or velocities) recorded at each receiver location into a wavefield modeling code. Here, we formulate an exact integral expression based on reciprocity theory that uses a combination of velocity-stress recordings and quadrupole-dipole backpropagating sources, rather than the commonly used approximate formula involving only particle velocity data and dipole backpropagating sources. The latter approximation results in two types of nonphysical waves in the scattered wavefield estimate: First, each arrival contained in the data is injected upward and downward rather than unidirectionally as in the true time-reversed experiment; second, all injected energy emits compressional and shear propagating modes in the model simulation (e.g., if a recorded P-wave is injected, both P and S propagating waves result). These artifacts vanish if the exact wavefield extrapolation integral is used. Finally, we show that such a formula is suitable for extrapolation of ocean-bottom 4C data: Due to the fluid-solid boundary conditions at the seabed, the data recorded in standard surveys are sufficient to perform backpropagation using the exact equations. Synthetic examples provide numerical evidence of the importance of correcting such errors.

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Section: Introductionmentioning

confidence: 99%