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The benefits of CGG technologies and services are regularly featured in the industry press. Find out more by consulting our e-library of published industry articles. Narrow your search by entering at least one search criterion:

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Consolidating rock-physics classics: A practical take on granular effective medium models

The Leading Edge, May, 2019
Fabien Allo
©2019 SEG

The paper presents a review of classic rock physics models used for clastic sedimentary rocks and how they have been combined into extended models through the introduction of a few parameters associated with a compositional or textural property of the rock. The models are used on a variety of real data sets to showcase how rock properties can be inferred from elastic properties.

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3D fault imaging using windowed Radon transforms: an example from the North Sea

First Break, May, 2019
Geoffrey Dorn
©2019 EAGE

The interpretation of fault surfaces is key to understanding the subsurface geology represented in 3D seismic volumes. The geologic structure represented by seismic reflections can be auto-tracked in the volume. Faults, however, are imaged as discontinuities or changes in curvature in the seismic data. For many years, fault interpretation involved manually picking fault cuts on orthogonal slices through the seismic volume. These fault cuts were grouped into conceptual faults, and 3D fault surfaces were created from the fault cuts.

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Full-waveform inversion for salt: A coming of age

The Leading Edge, March, 2019
Ping Wang | Zhigang Zhang | Jiawei Mei | Feng Lin | Rongxin Huang
©2019 SEG

Full-waveform inversion (FWI), proposed by Lailly and Tarantola in the 1980s, is considered the most promising data-driven tool to automatically build velocity models. Many successful examples have been reported using FWI to update shallow sediments, gas pockets, and mud volcanoes. However, successful applications of FWI to update salt structures had almost only been seen on synthetic data until recent progress at the Atlantis field, Gulf of Mexico (GoM). We revisited some aspects of FWI algorithms to minimize cycle-skipping and amplitude discrepancy issues and derived an FWI algorithm that is able to build complex salt velocity models. We applied this algorithm to a variety of data sets including WAZ (wide-azimuth) and FAZ (full-azimuth) streamer data as well as OBN (ocean bottom node) data with different geologic settings in order to: 1) demonstrate the effectiveness of the method for salt velocity updates, and 2) examine some fundamentals of the salt problem. We observe that in multiple cases, salt velocity models from this FWI produce subsalt images of superior quality. We demonstrate with one FAZ streamer data example in Keathley Canyon that we probably do not need very high frequency in FWI for subsalt imaging purposes. Based on this observation, we envision that sparse node for velocity (NFV) acquisition may provide appropriate data to handle large and complex salt bodies with FWI. We believe that the combination of advanced FWI algorithms and appropriate data acquisition will bring a step-change to subsalt imaging.

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Leveraging Legacy Data

Oilfield Technology, March, 2019
Jo Firth | Priyabrata Pradhan
©2019 Palladian Publications Ltd

In recent years, there have been many rapid developments in subsurface imaging, meaning that even data sets that are only two or three years old can benefit from reprocessing. Reprocessing older data, either on its own or in combination with new data, is both practical and cost-effective as new acquisition can be expensive and time-consuming, especially in areas where there are seasonal constraints due to climate, fishing or breeding seasons. The Cornerstone Evolution project in the Central North Sea demonstrates the value achieved by reprocessing a large number of older surveys in conjunction with newer acquisition.

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Australia: Depth Reprocessing Rejuvenates Gippsland Basin

Geo Expro, March, 2019
Peter Baillie | Paul Carter | Jarrad Grahame | Joe Zhou | Nigel Mudge
©2019 GeoPublishing Ltd

The world-class oil and gas fields of the Gippsland Basin, with original recoverable reserves of more than four billion barrels of oil and around ten trillion cubic feet of gas, were discovered following a 1962 2D seismic survey. Despite considerable exploration, it has long been known that unresolved seismic depth imaging issues have had a significant impact on data quality. As a consequence, the province probably has unrealised exploration potential, particularly in the deeper stratigraphic section. The basin-wide Gippsland ReGeneration reprocessing project by CGG has changed the paradigm and the basin is now seen as rejuvenated, with new exploration opportunities and significant upside potential.

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