3D Interferometric Extrapolation of SSP Marine Data

Proceedings of the 8th SEGJ International Symposium, 2006

One of the applications of Seismic Interferometry (SI) is the reconstruction of the Earth's reflection response from the crosscorrelation of seismic background noise recorded at the surface. In recent years, several authors have derived the relations that govern this process. The quality of the reconstruction has been extensively examined with numerical modeling results. Several authors have applied the method to real data for the reconstruction of surface waves. We applied SI to background-noise field data recorded in a desert area. The reconstructed results show several coherent events-inclined and nearly horizontal. The inclined coherent events are interpreted as reconstructed surface waves. The nearly horizontal coherent events appear to align well with reflections from an active survey along the same line. Therefore, we interpret these events as reconstructed reflections.

Journal of Applied Geophysics, 2011

One key step in seismic data processing flows is the computation of static corrections, which relocate shots and receivers at the same datum plane and remove near surface weathering effects. We applied a standard static correction and a wave equation datuming and compared the obtained results in two case studies: 1) a sparse ocean bottom seismometers dataset for deep crustal prospecting; 2) a high resolution land reflection dataset for hydrogeological investigation. In both cases, a detailed velocity field, obtained by tomographic inversion of the first breaks, was adopted to relocate shots and receivers to the datum plane. The results emphasize the importance of wave equation datuming to properly handle complex near surface conditions. In the first dataset, the deployed ocean bottom seismometers were relocated to the sea level (shot positions) and a standard processing sequence was subsequently applied to the output. In the second dataset, the application of wave equation datuming allowed us to remove the coherent noise, such as ground roll, and to improve the image quality with respect to the application of static correction. The comparison of the two approaches evidences that the main reflecting markers are better resolved when the wave equation datuming procedure is adopted.

Seg Technical Program Expanded Abstracts, 2006

Seismic Interferometry (SI) can construct reflection data from seismic background noise. In recent years, several authors developed the theory and applied it to synthetic data. With field data, the only success until now was the reconstruction of surface waves from coda and microseisms. Here, we attempt to reconstruct reflection events from noise data recorded in a desert area. The SI result shows inclined and horizontal coherent events. Some of the reconstructed events appear to align with reflections from an active survey. We cannot, however, exclude alternative explanations.

SEG Technical Program Expanded Abstracts 2012, 2012

In this paper we report on progress using ambient noise correlation with a dense 3D survey conducted in Long Beach, California, to estimate subsurface velocity. We show that both Rayleigh wave and body wave signals can be clearly observed between 0.2-10 Hz frequency range in the noise cross-correlations. The observed signals also compare well with an active source gather. We apply eikonal tomography to invert for the Rayleigh wave phase velocity maps at several different frequencies. The phase velocity maps, which are most sensitive to structure in the top 600 meters, show clear correlation with known surface features such as the slow anomaly adjacent to the coast in the south and a fast anomaly associated with the Newport-Inglewood fault zone. The results presented in this study show the potential of using ambient noise interferometry method to complement active source techniques in studying high-resolution shallow crustal structure.

The leading edge, 2012

2020

Controlled-source seismic exploration surveys are not always possible in nature-protected areas. As an alternative, application of passive seismic techniques in such areas can be proposed. In our study, we show results of passive seismic interferometry application for mapping the uppermost crust in the area of active mineral exploration in Northern Finland. We are utilizing continuous seismic data acquired by Sercel Unite Wireless multichannel recording system along several profiles during XSoDEx (eXperiment of SOdankylä Deep Exploration) project. The objective of the project was to obtain a structural image of the upper crust in the Sodankylä area of Northern Finland in order to achieve a better understanding of the mineral system at depth. The key experiment of the project was a high-resolution seismic reflection experiment, and continuous passive seismic data was acquired in parallel with reflection seismic data acquisition. Due to this, the length of passive data suitable for noise cross-correlation was limited to several hours. In addition, analysis of the passive data demonstrated that dominating sources of ambient noise are non-stationary and have different origin across the XSoDEx study area. As the long data registration period and isotropic azimuthal distribution of noise sources are two major conditions for diffuse wavefield necessary for Empirical Green's Functions (EGFs) extraction, the conventional techniques of passive seismic interferometry was not possible to apply. To find the way to obtain EGFs, we used numerical modelling to investigate the properties of seismic noise originating from sources with different characteristics and propagating inside synthetic heterogeneous Earth models that models real geological conditions in the XSodEx study area. The modelling demonstrated that scattering of ballistic waves on irregular shape heterogeneities, such as massive sulphides or mafic intrusions, could produce diffused wavefield composed mainly of scattered surface waves. This scattered wavefield can be used to retrieve reliable Empirical Green Functions (EGFs) from short-term and non-stationary data, using a special technique called "signal-to-noise ratio stacking" (SNRS). The EGFs calculated for the XSoDEx profiles were inverted in order to obtain S-wave velocity models down to the depth of 300 meters. The obtained velocity models agree well with geological data and complement the results of reflection seismic data interpretation.

Geophysics, 2009

Seismic Interferometry is rapidly becoming an established technique to recover the Green's function between receivers, but practical limitations in the source energy distribution inevitably lead to spurious energy in the results. Instead of attempting to suppress all such energy, we use a spurious wave associated with the crosscorrelation of refracted energy at both receivers to infer estimates of subsurface parameters. We name this spurious event the virtual refraction. Illustrated by a numerical two-layer example, we find that the slope of the virtual refraction defines the velocity of the faster medium and the stationary phase point in the correlation gather provides the critical offset. With the associated critical time derived from the real shot record, this approach includes all the necessary information to estimate wave speeds and interface depth without the need of inferences from other wave types.

First International Conference on Engineering Geophysics, 2011

The steeply dipping and irregular topography of the water bottom represents a challenge to the accurate imaging of the reservoirs using surface seismic methods. Creating seismic wave with artificial sources and observing the arrival time of the waves reflected from acoustic impedance contrasts or refracted through high velocity members in conventional source location and interpolation methods heavily rely on the accuracy of the velocity models. In this paper interferometric techniques will be use to extract multiple scatter information in ocean bottom seismic data which will provide reliable results with and without knowledge of the velocity models. The sparse ocean bottom seismic data are interferomatically correlated with the model – based Green’s functions for the sea floor model. This generates densely recorded ocean bottom seismic traces. Local matching filter will be applied to reduce the artifacts in the interpolated data. To mitigate the artifacts in the interferometry correlation results, an anti – aliasing theory developed will establish a fundamental criterion for numerical application of seismic interferometry to any seismic data. Mathematical Time Revisal Mirror models will be developed in MATLAB to determine the position of seismic source by comparing the phases of signals at the output terminals. Simulation will also be run using the data generated to plot a two dimensional ocean bottom seismic profile (OBS). A time migration and depth migration methods were applied to the ocean bottom seismic profile to determine which methods give accurate imaging of reservoir using the interferometric migration. Hence seismic interferometry can be applied during exploration for hydrocarbon and during down hole drilling to provide reliable information about complex geology.

Proceedings, 2013