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The recent world-class Baleine discovery within the Deep Tano Basin has attracted renewed exploration interest for the offshore Côte d’Ivoire. Its structural complexity and depositional stratigraphy, resulting from multiphase rifting of this basin, require high-quality seismic data to develop detailed geological models. To achieve this, CGG recently conducted a seismic stratigraphic analysis using the CDI-14 broadband multi-client 3D seismic dataset over the Grand Bassam subbasin. The goal was to develop new insights into Late Cretaceous depositional mechanisms and key facies distribution to shed light on the potential prospectivity of this basin.

This paper describes a successful reservoir characterization workflow where geostatistical inversion was first carried out to characterize caves and vugs, and then azimuthal inversion was used to obtain fractures strike and density. It improves the precision of reservoir prediction, and effectively characterizes the distribution of all kinds of reservoir including caves, vugs, fractures strike and density in the carbonate reservoirs. The predictions are well matched against the reservoir information from a newly drilled well.

We present a method to estimate and correct the phase of broadband seismic data in the low-frequency range using the tomography velocity model as an analogy for subsurface geology. The high-resolution velocity model is obtained from travel-time tomography and therefore has minimal influence from seismic amplitude and phase in the low-frequency range. We derive a phase-correction operator by matching between seismic data and zero-phase synthetics that are built based on a realization of reflectivity obtained from the tomographic inversion. We discuss the robustness of the method with synthetic data and show real data examples demonstrating improved well-tie and impedance inversion results.

In recent years there has been tremendous progress in the resolution and accuracy that can be obtained in seismic images. Several techniques are now available to achieve a high-definition final image. In the Cap-Boujdour dataset from offshore Morocco, the imaging is challenging due to a highly faulted geological setting and the presence of gas hydrates in the shallow overburden. The final image resolution beneath these absorptive bodies is poor if we do not compensate for the resulting attenuation. This case study illustrates how a combination of sophisticated velocity update technologies, such as full waveform inversion and the latest tomography developments, together with Q-prestack depth migration, can achieve high-resolution seismic imaging.

This study is concerned with testing the application of Automated Mineralogy (AM), specifically QEMSCAN, to identify and quantify microplastic particles within a solid heterogeneous specimen, as an initial assessment of how this technique may be utilised in microplastic research and environmental monitoring. It utilises a novel sample preparation method and makes significant alterations to standard QEMSCAN operating parameters to analyse model samples of known composition. This paper outlines initial results and highlights the key challenges in applying QEMSCAN to this area, suggesting potential solutions for future development of the technique.

A continuing concern regarding presalt carbonate reservoirs offshore Brazil is how to derive accurate quantitative estimates of reservoir properties. It is challenging to understand the link between the facies model and the variation in elastic properties, recover a reliable model of elastic properties from seismic, estimate porosities and permeabilities to use in reservoir simulations, and ultimately close the loop in integrated geology and engineering workflows. This case study describes our use of geostatistical inversion as a tool to unlock reservoir properties. We show how the integration of diverse information from various sources and at different scales is used to produce a meaningful range of probabilistic realizations of this Brazilian deepwater presalt reservoir.

Short-period multiple attenuation is often challenging as the multiple generators are typically not sufficiently well recorded as primary events for SRME to be successful. Model-based approaches have traditionally been used to circumvent this problem but may only model multiples generated by key events such as the waterbottom. Deconvolution-based alternatives offer the possibility to model multiples from more short-period multiple generators, but in practice many acquisition geometries are not well suited to higher-dimensional deconvolution implementations. We discuss a wave-equation deconvolution approach (WEDecon) which derives its prediction operator in the image domain. The image is then used to predict multiples which are subtracted from the data. We highlight the flexibility of WEDecon using data examples from towed-streamer, OBN and land geometries. The WEDecon approach has been successful at significantly reducing levels of residual multiple present in all these data types. We acknowledge, however, that short-period multiple attenuation is still a challenging topic and that further work is necessary in this area.

Full-waveform inversion has been established as a standard tool for building high-resolution velocity models. To take full advantage of such models, the migration algorithm must be capable of handling fine-scale geo-bodies and sharp contrasts while affordably producing high-frequency migration stacks and gathers. Even though ray-based Kirchhoff migration can efficiently generate high-resolution migration stacks and gathers, the calculation of traveltimes becomes inaccurate and unstable near large velocity variations, sharp contrasts, and complex structures. Reverse[1]time migration (RTM), on the other hand, can accurately handle complex velocity models with fine details and sharp contrasts due to its deployment of full-wavefield propagation. However, the cost of RTM becomes prohibitive when high-frequency stacks and gathers are required. Following this idea of wave-equation-based traveltimes, we propose a wave-equation Kirchhoff (WEK) scheme that performs Kirchhoff migration using maximum-amplitude traveltimes and amplitudes from the wavefield. These traveltimes and amplitudes are computed through affordable low-frequency full-wavefield propagation. WEK not only partly inherits the benefit of full-wavefield propagation for high-resolution models, but it also maintains the affordability of ray-based Kirchhoff migration. We use synthetic and field data to evaluate this method and compare the WEK results with those from ray-based Kirchhoff migration and RTM.

High-quality depth images typically require accurate high resolution representations of the earth model. Full-waveform inversion (FWI) has recently justified its value throughout the industry in providing high-resolution velocity models. However, obtaining an accurate FWI velocity model using narrow-azimuth streamer data can still be challenging in complex geologic environments. The uncertainties, often caused by relatively low resolution perpendicular to the shooting direction and weaker illuminations areas, instill less confidence for reservoir delineation and depth mapping. In this case study from offshore Senegal, we present a joint velocity (Vp) and epsilon (?) multi-azimuth FWI workflow to construct a high-resolution model to overcome severe image distortion. The updated model improved event focusing and gather flatness and demonstrated significant imaging uplifts consistent with our understanding of the geology in the area.