Wavefield decomposition based on acoustic reciprocity: Theory and applications to marine acquisition

Abstract

In marine seismic acquisition, the free surface generates seismic events in our recorded data that are often categorized as noise because these events do not contain independent information about the subsurface geology. Ghost events are considered as such noise because these events are generated when the energy generated by the seismic source, as well as any upgoing wavefield propagating upward from the subsurface, is reflected downward by the free surface. As a result, complex interference patterns between up-and downgoing wavefields are present in the recorded data, affecting the spectral bandwidth of the recorded data negatively. The interpretability of the data is then compromised, and hence it is desirable to remove the ghost events from the data. Rayleigh's reciprocity theorem is used to derive the relevant equations for wavefield decomposition for multisensor and single-sensor data, for depth-varying and depth-independent recordings from marine seismic experiments using a single-source or dual-source configuration. A comparison is made between the results obtained for a 2D synthetic example designed to highlight the strengths and weaknesses of the various acquisition configurations. It is demonstrated that, using the proposed wavefield decomposition method, multisensor data (measurements of pressure and particle velocity components, or multidepth pressure measurements) allow for optimal wavefield decomposition as independent measurements are used to eliminate the interference patterns caused by the free surface. Single-sensor data using constant-depth recordings are found to be incapable of producing satisfactory results in the presence of noise. Single-sensor data using a configuration with depth-varying measurements are able to deliver better results than when constant-depth recordings are used, but the results obtained are not of the same quality when multisensor data are used.

Angular coherence in ultrasound imaging: Theory and applications

“…36 A further detailed introduction to the theorem can be found in Fokkema et al 37 In acoustics, the theorem has been applied in time-reversal acoustics, 36,38 seismic measurement 39 and marine acquisitions. 40 In modern scattering theory, the reciprocity theorem is expressed by the symmetry of the scattering matrix. 34 The theorem is valid for forward and inverse scattering, 41,42 as well as in the presence of absorption 38 and multiple scattering.…”

Joint up/down decomposition and reconstruction using three‐component streamers with or without ghost model: the sampling theory

“…If measurements are only available on one boundary, we need to combine the appropriate expressions derived from the field-reciprocity and power-reciprocity theorems. In addition, van Borselen, Fokkema, and van den Berg (2013) show that the integral can be avoided by adopting various assumptions. We will summarise relevant results of van Borselen et al 2013 in the subsequent two subsections.…”

“…In addition, van Borselen, Fokkema, and van den Berg (2013) show that the integral can be avoided by adopting various assumptions. We will summarise relevant results of van Borselen et al 2013 in the subsequent two subsections.…”

Target‐level waveform inversion: a prospective application of the convolution‐type representation for the acoustic wavefield

“…In this work, we apply the proposed waveform inversion method for a horizontal well acquisition geometry (Mehta et al 2010), where the sources are located at the surface and the receivers are located along a horizontal well at the target level. For the receivers, we have used both hydrophones and geophones to measure the pressure and the vertical particlevelocity fields, which are used to perform the up/down wavefield decomposition (Amundsen and Reitan 1995;Schalkwijk, Wapenaar and Verschuur 2003;van Borselen, Fokkema and van den Berg 2013). For this type of acquisition geometry, TLWI becomes completely independent of the medium parameters above of the target level, in the sense that we do not need to know the medium parameters from this zone to perform the waveform inversion process.…”