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Porosity prediction using cokriging with multiple secondary datassets

CSEG - Canadian Society of Exploration Geophysicists, March, 2016
Kiki Hong Xu | Brian Russell
©2016 CSEG

The prediction of porosity is essential for the identification of productive hydrocarbon reservoirs in oil and gas exploration. Numerous useful technologies have been developed for porosity prediction in the subsurface, such as multiple attribute analysis, kriging, and cokriging. Kriging allows us to create spatial maps from point information such as well log measurements of porosity. Cokriging combines well log measurements of porosity with seismic attributes recorded between the wells to improve the estimation accuracy of the overall map. However, the traditional cokriging for porosity estimation is limited to only one seismic attribute. To introduce more geological information and improve the accuracy of prediction, we develop a new cokriging system that extends traditional cokriging to two secondary variables. In this study, our new cokriging system is applied to the Blackfoot seismic data from Alberta, and the final estimated map is shown to be an improvement over kriging and traditional single attribute cokriging. To show this improvement, "leave-one-out" cross-validation is employed to evaluate the accuracy of porosity prediction with kriging, traditional cokriging, and our new approach. Compared to kriging and traditional cokriging, an improved porosity map, with higher lateral geological resolution and smaller variance of estimation error, was achieved using the new cokriging system. We believe that the new approach can be considered for porosity prediction in any area of sparse well control.

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Nearfield hydrophone driven 3D source designature and deghosting for multi-level source data

EAGE workshop/forum/local conference, November, 2015
Gordon Poole | Ping Wang | Yuan Ni | Zhan Fu | Risto Siliqi
©2015 EAGE

Combined with recent receiver deghosting strategies, the use of multi-level sources can provide further uplift to the ever broadening bandwidth of seismic data. While multi-level sources help mitigate source notches in the output spectrum, the resulting emitted wavelet still exhibits residual ghosts, directivity, and bubble energy which must be handled in processing. We highlight the compatibility of Ziolkowski’s notional source method with multi-level source acquisition. We continue by showing how the directional signatures may be used for 3D directional designature and deghosting on shallow water towed streamer data. The results show a significant improvement in the level of ringing relating to source wavelet directivity effects.

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Nearfield hydrophone driven 3D source designature and deghosting for multi-level source data

EAGE workshop/forum/local conference, November, 2015
Gordon Poole | Ping Wang | Yuan Ni | Zhan Fu | Risto Siliqi
©2015 EAGE

Combined with recent receiver deghosting strategies, the use of multi-level sources can provide further uplift to the ever broadening bandwidth of seismic data. While multi-level sources help mitigate source notches in the output spectrum, the resulting emitted wavelet still exhibits residual ghosts, directivity, and bubble energy which must be handled in processing. We highlight the compatibility of Ziolkowski’s notional source method with multi-level source acquisition. We continue by showing how the directional signatures may be used for 3D directional designature and deghosting on shallow water towed streamer data. The results show a significant improvement in the level of ringing relating to source wavelet directivity effects.

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Efficient Harmonic-Distortion Mitigation on Vibro-Seismic Sources

EAGE - European Association of Geoscientists and Engineers, November, 2015
Kaelig Castor | Thomas Bianchi | Olivier Winter | Thierry Klein
©2015 EAGE

In seismic land acquisition, harmonic–noise in vibrator ground-force has always been a major limitation in terms of data quality and productivity. In high productivity acquisition, vibrator distortion is usually prevented by waiting enough time between successive shots. Otherwise, it has to be reduced during seismic data processing. The low-dwell sweeps that are now currently used in production can induce even more important distortion issues. Harmonics from low frequency content can be considerably more spread out over time after correlation. Consequently, the extensive use of the low-frequency bandwidth for vibro-seismic sources prompted the need for improved distortion control, especially at low frequency. This paper describes a method to mitigate the harmonic distortion directly before emission. The output noise is measured and injected adaptively with opposite phase in the source input to converge towards an ideal output. The results show important noise reduction over the full bandwidth, with perfect low-frequency fidelity. A better source signal quality provides better seismic data that is easier to process, and opens new possibilities in terms of acquisition scenarios with possible productivity improvement.

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Success of high-resolution volumetric Q-tomography in the automatic detection of gas anomalies on offshore Brunei data

SEG - Society of Exploration Geophysicists, October, 2015
Fatiha Gamar | Diego Carotti | Patrice Guillaume | Amor Gacha | Laurent Lopes
©2015 SEG

Over recent years, many authors have proposed to compensate the absorption loss effects inside of the imaging process through the use of an attenuation model. This is more particularly necessary in the presence of strong attenuations anomalies. Q tomography has been developed for estimating this attenuation model but is generally limited to estimating attenuation in predefined anomalies. In this paper, we show how we managed to reveal automatically shallow gas pockets on the complex offshore Brunei dataset by using a high-resolution volumetric Q tomography. A key component of our approach is the estimation of effective attenuation in the pre-stack data domain through accurate picking of the frequency peak. Finally we used the Q-model to compensate for absorption in the imaging process.

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