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Results
The Fidelity of 3D Wavefield Reconstruction From a Four-Component Marine Streamer and its Implications for Time-Lapse Seismic Measurements
Eggenberger, Kurt (Schlumberger) | Christie, Philip (Schlumberger) | van Manen, Dirk-Jan (Schlumberger) | Vassallo, Massimiliano (Schlumberger) | Özbek, Ali (Schlumberger) | Zeroug, Smaine (Schlumberger)
Summary It is well documented in time-lapse (or 4D) seismic literature that the non-repeatability of the acquisition geometry is the single-most important factor contributing to a residual noise floor for the 4D seismic signal from the reservoir. To compensate for imperfect receiver repositioning, wavefield regularization techniques can be applied to allow for wavefield matching common to both vintage surveys. Typically, a trade-off is made between reducing the receiver positioning mismatch and the imperfections introduced by wavefield spatial aliasing due to acquisition geometry and geology. Wavefield reconstruction techniques are at the core of this paper, however with a different underlying basis than that for conventional approaches. Through use of towed 3D four-component (4C) marine seismic streamers and the application of matching pursuit interpolation processing techniques, a 3D reconstructed and deghosted pressure wavefield can be obtained on a densely sampled grid that permits wavefield matching to vintage positions in an unprecedented, effective way, as recently demonstrated by Özbek et al. (2010). This paper focuses on quantifying the fidelity of the wavefield reconstruction and discusses the implications of such 4C acquisition and processing on 4D seismic measurements. Based on data analysis from an experimental 3D-4C test, the findings from the assessment presented in this paper are three-fold: firstly, the pressure recordings of the new 3D-4C acquisition system are found to be fully comparable to that of the existing production, hydrophone-only counterpart, used as a benchmark. Hence, established 4D characteristics for the benchmark system remain valid for the pressure recording of the 4C system. Secondly, the uniformly sampled pressure cube, output by the multicomponent seismic wavefield reconstruction, compares favorably with the recorded and uninterpolated pressure benchmark, contributing to establishing the integrity of the reconstructed wavefield. Thirdly, the 3D-4C-enabled wavefield reconstruction is found to furnish superior performance as compared to a hydrophone-only state-of-the-art interpolator, in particular, in areas with significant cable feathering. Overall, we find this 4C seismic acquisition and processing approach to offer the prospect of significantly reducing the effects of receiver mispositioning, leading to marked improvements of the 4D results. The source mispositioning becomes the critical limiting factor on the acquisition side to ensure high seismic repeatability - a limitation, however, that can be addressed effectively through available source steering technology.
- Europe > Norway > North Sea > Northern North Sea > North Viking Graben > PL 104 > Block 30/9 > Oseberg Field > Tarbert Formation (0.99)
- Europe > Norway > North Sea > Northern North Sea > North Viking Graben > PL 104 > Block 30/9 > Oseberg Field > Oseberg Formation (0.99)
- Europe > Norway > North Sea > Northern North Sea > North Viking Graben > PL 079 > Block 30/9 > Oseberg Field > Tarbert Formation (0.99)
- (3 more...)
Effective Seismic Interference Elimination Enabled by Multi-Component Data From Marine Acquisitions
Vassallo, Massimiliano (WesternGeco) | Eggenberger, Kurt (WesternGeco) | van Manen, Dirk-Jan (WesternGeco) | Rentsch, Susanne (WesternGeco) | Brouwer, Wouter (WesternGeco) | Özbek, Ali (Schlumberger)
Summary We present a fast and effective method to detect and eliminate seismic interference from 3D marine data measured by four-component (4C) streamers. The interference elimination method we propose acts on each shot record independently from the others, relying on the pressure wavefield being reconstructed (and simultaneously deghosted) on a 2D grid, densely sampled in both the inline and the crossline directions. Such reconstruction is enabled by matching-pursuit-based signal processing techniques proposed recently in the literature that have the capability to explicit the information in the multicomponent measurements. Without these measurements, the reconstruction capability is seriously compromised by the strong crossline aliasing. We show that the interference can be easily isolated and removed from the data, with a high degree of signal preservation, after the data are reconstructed on a dense grid of receivers. When supported by vector based seismic interference detection, this technique has the potential of being automated and applied directly during the acquisition timeframe.
Combination of Multi-Component Streamer Pressure and Vertical Particle Velocity: Theory and Application to Data
Caprioli, Philippe (WesternGeco) | Özdemir, Kemal (WesternGeco) | van Manen, Dirk-Jan (WesternGeco) | Mahat, Shipra (WesternGeco) | Özbek, Ali (Schlumberger) | Kragh, Ed (Schlumberger) | Christie, Phil (Schlumberger)
Summary In this paper, we generalize the optimal deghosting (ODG) method used for deghosting over/under data to combine pressure (P) and vertical velocity (Z) data recorded with a 4C multi-component streamer to reduce the impact of the noise on the deghosted data. The ODG approach uses pressure and velocity ghost models and the statistics of the residual noise to minimize, in a least-squares sense, the noise on the up-going/deghosted wavefield. ODG and the standard PZ summation (PZSUM) combinations are applied to pressure and velocity data recorded in the North Sea (2-D acquisition). We show that both methods attenuate the receiver ghost, fill in information at the pressure notch frequencies and that ODG has the least post-combination noise level. We also show pre- and post-stack vertical velocity data with encouraging signal-to-noise ratios. Some differences between the ODG and PZSUM combination results can be explained using the cross-line component measurement. Finally, in order to further improve the PZ deghosted data, we suggest a toolbox approach that takes advantage of both ODG and PZSUM combinations and accounts for the varying signal-to-noise ratios observed on multi-component streamer data.
- Europe > United Kingdom > North Sea (0.24)
- Europe > Norway > North Sea (0.24)
- Europe > North Sea (0.24)
- (2 more...)
Contributions of the Horizontal and Vertical Components of Particle Velocity in 3D Pressure Wavefield Reconstruction on Dense Receiver Grids Using Generalized Matching Pursuit
Vassallo, Massimiliano (WesternGeco) | Eggenberger, Kurt (WesternGeco) | van Manen, Dirk-Jan (WesternGeco) | Özdemir, Kemal (WesternGeco) | Robertsson, Johan (ETH Zürich) | Özbek, Ali (Schlumberger)
Summary Multichannel 3D reconstruction and deghosting techniques based on multicomponent streamer measurements of the pressure wavefield and its associated gradients were recently introduced in literature. In particular, the Generalized Matching Pursuit (GMP) technique was applied to multicomponent 3D synthetic data bringing significant improvements to address the aliasing arising from sparse crossline sampling. In this abstract, we present an example of real data acquired by an experimental 3D towed multicomponent cable array and show the performance of GMP applied to the multicomponent measurements. The real data examples illustrate that GMP reconstructs and deghosts the pressure wavefield onto a 2D receiver grid uniformly sampled at 6.25 m in both, the inline and the crossline directions, starting from a very limited number of crossline samples at realistic spacings (i.e., 75 m). We analyze the contribution of each component to the overall crossline reconstruction. We show that the crossline component of particle velocity is the key enabler for GMP to produce a very effective and robust reconstruction of the three-dimensional wavefield back-scattered by the subsurface for each recorded seismic shot.
- North America > United States (0.16)
- Europe (0.16)