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We describe opportunities and challenges for imaging seismic data acquired using conventional marine sources and receivers located on the seafloor. Opportunities include the promise of greater imaging resolution than sea-surface acquisition and processing can offer, especially using P-wave to S-wave converted reflection energy (PS imaging). Challenges include effects of current seafloor receiver spacing, which can be large enough to negate the promised resolution gains. We use a synthetic dataset to illustrate possible imaging improvements that can result from seafloor acquisition, as well as image degradation that can result when seafloor receivers are separated by typical current distances.

We present a method to enhance the bandwidth of seismic data in the continuous wavelet transform (CWT) domain. By utilizing the features of CWT in detecting time-variant frequency content and automatically designing band-dependent time window, we can enhance the seismic bandwidth mostly based on signal. A high-dimensional implementation of the method enables us to make full use of the information from nearby data to stabilize the algorithm. A real data example shows that applying the proposed method at different processing stages has different benefits. If implemented properly, the approach is AVO friendly and a better alternative to conventional spectrum balancing.

This paper is an attempt to fill the technology gap existing between pure P- and PS-wave imaging. Full
wavefield extrapolation techniques are well developed for P-wave and RTM has been now available for
almost a decade. Conversely, ray based migration algorithms are still the workhorse for converted-wave
(PS-wave) depth imaging. Here, we introduce a new converted-wave anisotropic RTM, using a low-rank
decomposition of mixed-domain space-wavenumber propagators for quasi-P and quasi-S waves. These
operators are formal integral solutions of the pure-mode wave equations which guarantee stable and
dispersion-free time extrapolation for coarse time steps in anisotropic, heterogeneous media. The puremode extrapolators are attractive for both PS-wave structural imaging and velocity analysis. An ocean
bottom cable synthetic example illustrates the effectiveness of low-rank PS-wave RTM when compared
against state-of-the-art Gaussian beam and finite difference RTM algorithms.

Least squares migration (LSM), like interpolation, has the potential to address sampling issues and generate images with better amplitudes than migration. Although both techniques share the same goal and often the same formulation, they differ on the nature of the model that is used to predict the data. For LSM the cost of the migration/modelling operator bring limitations. In this abstract I discuss some of these limitations, possible ways to overcome them, and analyse some similarities and differences with respect to interpolation. Also I present results using a LSM implementation for Kirchhoff Depth Migration for both PP and PS data.

In ocean bottom acquisition, receiver side deghosting is normally done by summing together the hydrophone P and geophone Z data. A prerequisite for this method to work effectively is the precise calibration of geophones to hydrophones, so as to compensate for the differences in sensitivity and coupling. A “cross-ghosting” approach has been proposed to extrapolate geophone and hydrophone data to have the same manner for matching. However, as far as we know, existing cross-ghosting methods are based on a 1D geology assumption. In this paper, we describe a cross-ghosting method using 2D wave-equation extrapolation, which accurately predicts the ghost according to the structure of the seafloor.

Low frequency information is required for quantitative reservoir characterization. Because borehole measurements are often (laterally) sparse and preferential towards reservoir locations, there is much uncertainty on the low frequency models away from well control. Methods to improve the reliability of the low frequency data include the use of low frequency update schemes or seismic attribute maps. The use of seismic velocity data for trend modeling is well recognized, but the methodology for incorporating the velocity is not always clearly described. Especially in case of an AVO/AVA study, a rigorous workflow is desired. Here, we propose a method to include seismic velocity data. The methodology uses local geological knowledge through rock physics relations. We validate by comparing results of a more common method with our proposed workflow at blind wells. This shows that a low frequency model that does not use the velocity data misses significant (lateral) variations that are representative for the local geology.

A case study of the acquisition and background to the integrated multi-client geoscience project over the Gabon South basin.The deepwater area of the Gabon South basin is one of the last underexplored areas of the West Africa Atlantic Margin. CGG is acquiring and imaging a large broadband, multi-client 3D survey, covering over 25,000 km2 in this area, which will form the cornerstone of a major, integrated G&G study of the region.

Successful development of known fields requires high-quality seismic data in order to accurately delineate the reservoir through processes such as seismic inversion and reservoir characterization studies. In the new oil price regime this has become even more important as oil companies try to keep the total cost of production down while at the same time optimizing the life of the field. Tailored seismic acquisition designs with complementary imaging technology matched to the local geology provide seismic data that better meets the objectives for each reservoir.

Article describes application of TomoML to our 35,000 km2 Cornerstone survey in the North Sea. Also make reference to broadband deghosting, dip-constrained channel tomography and dual azimuth.