J. Singer

Retrieval of reflections from seismic background‐noise measurements

The retrieval of the earths reflection response from cross?correlations of seismic noise recordings can provide valuable information, which may otherwise not be available due to limited spatial distribution of seismic sources. We cross?correlated ten hours of seismic background?noise data acquired in a desert area. The cross?correlation results show several coherent events, which align very well with reflections from an active survey at the same location. Therefore, we interpret these coherent events as reflections. Retrieving seismic reflections from background?noise measurements has a wide range of applications in regional seismology, frontier exploration and long?term monitoring of processes in the earths subsurface.

Synthetic aperture controlled source electromagnetics

Controlled?source electromagnetics (CSEM) has been used as a de?risking tool in the hydrocarbon exploration industry. Although there have been successful applications of CSEM, this technique is still not widely used in the industry because the limited types of hydrocarbon reservoirs CSEM can detect. In this paper, we apply the concept of synthetic aperture to CSEM data. Synthetic aperture allows us to design sources with specific radiation patterns for different purposes. The ability to detect reservoirs is dramatically increased after forming an appropriate synthetic aperture antenna. Consequently, the types of hydrocarbon reservoirs that CSEM can detect are significantly extended. Because synthetic apertures are constructed as a data processing step, there is no additional cost for the CSEM acquisition. Synthetic aperture has potential for simplifying and reducing the cost of CSEM acquisition. We show a data example that illustrates the increased sensitivity obtained by applying synthetic aperture CSEM source.

3-D Controlled Source Electromagnetic (CSEM) interferometry by multi-dimensional deconvolution

SUMMARY Controlled Source Electromagnetic (CSEM) is an important technique in hydrocarbon exploration because it uses the large contrast in electrical resistivity to distinguish between water and hydrocarbons. In a shallow sea environment, the airwave that is refracted from the air-water interface dominates the recorded signal at large offsets. Therefore, the hydrocarbon detection ability of the CSEM is weakened because the airwave is independent of the properties of the subsurface. For a layered earth model, we apply multi-dimensionaldeconvolution interferometry to synthetic 3D CSEM data and estimate the reflection response of the subsurface. The difference in the models with and without a resistive layer is significantly increased by the employed interferometric analysis. However, the required receiver spacing is much denser than that of current CSEM surveys. In order to apply this technique to a field survey, we are currently working on how to relax the required receiver criterion for this technique.

Seismic Interferometry on background‐noise field data

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.

Steering and focusing diffusive fields using synthetic aperture

Although beam steering and focusing have been used for waves in many important ways, the application of these concepts to diffusive fields has not been wide spread because of the common belief that diffusion lacks directionality and therefore can neither be steered nor focused. We use the similarities between diffusion and waves and prove that diffusive fields can be steered and focused both in the frequency domain and in the time domain. This finding has the potential of extending the use of diffusive fields as a diagnostic tool in science.

Increasing the sensitivity of controlled source electromagnetics by using synthetic aperture

Controlled-source electromagnetics (CSEM) has been used as a de-risking tool in the hydrocarbon exploration industry. Although there have been successful applications of CSEM, this technique is still not widely used in the industry because the limited types of hydrocarbon reservoirs CSEM can detect. In this paper, we apply the concept of synthetic aperture to CSEM data. Synthetic aperture allows us to design sources with specific radiation patterns for different purposes. The ability to detect reservoirs is dramatically increased after forming an appropriate synthetic aperture antenna. Consequently, the types of hydrocarbon reservoirs that CSEM can detect are significantly extended. In this paper, we mainly show one type of synthetic aperture antenna whose field can be steered into a designed angle. Consequently, the field concentrates on the target reservoir and the airwave is reduced. We show a synthetic example and a data example to illustrate the increased sensitivity obtained by applying synthetic aperture CSEM source. Because synthetic apertures are constructed as a data processing step, there is no additional cost for the CSEM acquisition. Aside from the applications to marine CSEM, synthetic aperture can be widely applied to other electromagnetic methods such as on land electromagnetics and bore hole electromagnetics.

Seismic Interferometry Applied to Passive Data

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. We applied SI to background-noise field data recorded in a desert area. The reconstructed results show several coherent events which align well with reflections from an active survey along the same line.