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Full-waveform inversion (FWI) has demonstrated tremendous potential to provide high-resolution subsurface models. However, obtaining an accurate FWI velocity model can still be challenging in steep continental slope shelf geologic environments. The uncertainties, often caused by shallow abrupt velocity contrasts, limited diving-wave penetration depth, and weaker illuminations instill less confidence in reservoir depth mapping. In this case study from offshore Senegal, we present a visco-acoustic dynamic resolution time-lag FWI (DR-TLFWI) workflow to construct a more accurate high-resolution model. The newly updated model further reduces residual undulations, which improves gather flatness and event continuity. The cumulative improvements increase the interpretation confidence and enable better reservoir delineation in this area.

Historically, Brazilian pre-salt fields have been imaged by narrow-azimuth towed-streamer (NATS) data. More recently, ocean bottom node (OBN) acquisitions have been employed to image and monitor already producing fields. In cases as such, 4D seismic monitoring is only possible via NATS/OBN hybrid pairs, where NATS and OBN data sets serve as base and monitor, respectively. This hybrid configuration implies low repeatability. Extracting subtle 4D changes in hard pre-salt carbonate reservoirs can be challenging. Considering this, we propose a joint 4D full-waveform inversion (FWI) formulation to overcome low repeatability between different seismic surveys. We demonstrate promising results using a field data set from Santos Basin, where realistic 4D anomalies can be identified.

Surface-related multiple elimination (SRME) is an effective and widely used tool for the attenuation of multiple energy in marine seismic data. However, removing multiples with SRME is still challenging in geologically complex areas, and we often observe residual multiples in such settings. Residual multiples can be caused by poor sampling of near offsets, low signal-to-noise ratio (S/N), and cross-talk among different orders of multiples. To remove strong residual multiples, we propose a targeted SRME flow where we demigrate the generators of the strongest residual multiples and predict an SRME model with demigrated data as input. We present applications of this method on two field data examples in the deepwater Gulf of Mexico, where the targeted residual multiples are effectively attenuated.

As demonstrated by recent exploration success, Viridien’s Northern Viking Graben (NVG) seismic survey in the Northern North Sea has already proven to be a valuable exploration tool. Thanks to the high-quality seismic data in this geologically challenging area, prospects are better defined, allowing for qualified drill decisions. In 2024, Viridien applied the latest seismic acquisition and imaging technology to add a northern extension, known as NVG24, to its current coverage over the NVG so that it now extends into the Møre Basin and Møre Platform in the Norwegian Sea. A glimpse of the early fast-track data from NVG24 is shown in the foldout juxtaposed with fully imaged data from the NVG EW coverage. The upcoming NVG24 final data will be of the same high quality and reveal structural and stratigraphic details at the Manet Ridge, Marulk Basin, Gnausen High and the Møre Platform.

Viridien drills down into the prospectivity of Côte d’Ivoire’s Tano Basin while sharing the final data from its multi-client CDI23, 3D PSDM re-imaging project.

This case study demonstrates how a long-offset, wide-azimuth four-component OBN survey, in combination with Full-Waveform Inversion, can be used to produce detailed 3D images and a geobody of the Sleipner CO2 plume that can be used for quantitative analysis.

Our Head of Geoscience explains how Viridien’s latest seismic technologies, such as full-waveform inversion and the Sercel Tuned Pulse Source (TPS), are delivering outstanding early-out results on this next-generation multi-client program.

Ultra high-resolution (UHR) marine seismic is a scaled-down version of conventional seismic acquisition. Source-receiver separation and depth, shooting rate and seismic wavelengths are typically ten times smaller than for conventional seismic operations. Under ideal conditions, ten times higher subsurface resolution may be achieved, but there will also be less depth penetration due to anelastic damping of the high-frequency seismic waves.

A comprehensive seismic reservoir characterization study was conducted in a gas field in Argentina, utilizing geostatistical AVA seismic inversion to generate inputs for reliable static models and dynamic simulation. The study encompassed a range of disciplines, including petrophysics, rock physics modelling and geostatistical AVA seismic inversion followed by effective porosity co-simulation. The key advantage of the geostatistical inversion method lies in its ability to integrate all available data, including wells, seismic, and geological knowledge, and generate reasonable outcomes that honour all inputs. Notably in this study, the use of 3D prior proportions for geostatistical inversion proved to be crucial for better characterization of litho-facies across the area, outperforming the 1D prior proportions approach. The results of the geostatistical inversion, conceptual depositional model, and previous seismic attributes study showed significant consistency, increasing confidence in the outcomes of the geostatistical inversion. The results of this study will be used to build static models of the field, enabling the estimation of in-place gas volume and its associated uncertainty. These models will also serve as input for dynamic simulations for future development of this field.