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The Trion field in the western Gulf of Mexico (GoM) exhibits folded sediment beddings and strong attenuation bodies, which pose great challenges for seismic imaging. After a decade of processing effort employing the latest imaging technology, the available towed-streamer data for this area hit a technical limit. Improvements to velocity models and images were incremental, and it was determined that better data were needed to make a step change in image quality. To this end, an ocean bottom node (OBN) acquisition was carried out in late 2020 to record full- azimuth and long-offset seismic data with good low- frequency content. Time-lag FWI (TLFWI) using this OBN data was able to improve the tilted orthorhombic (T-ORT) velocity models, which led to better migrated images from least-squares (LS) Kirchhoff and reverse time migration (RTM). However, the reservoir image below the shallow absorption anomalies remained unsatisfactory. As an alternative imaging product, the FWI Image from TLFWI showed better structural continuity and more coherent amplitudes at the reservoir than LS-Kirchhoff or LSRTM.

Targeting of stratigraphic traps is rapidly becoming a successful exploration strategy, especially in relatively mature basins where a high proportion of structural traps have been tested. The development of robust geological and trap models, integrated with the results of seismic inversion, are key steps in mitigating the larger uncertainty and risk associated with exploration for stratigraphic traps. This study demonstrates the benefit of a fully integrated workflow, involving the interpretation and analysis of geophysical and geological data, to ensure the development of a robust prospect model. In this case, a new stratigraphic trapping concept has been developed within the Upper Jurassic Hanifa Formation a unit which is generally considered to consist of low porosities based on existing well control

We propose a laterally constrained surface wave inversion to obtain a reliable near-surface shear-wave velocity field from Rayleigh wave measurements. This workflow is targeted at dense 3D broadband Wide-Azimuth land surveys, aiming to obtain reliable and realistic lateral shear-wave velocity variations pertinent with regard to surface or sub-surface information. We applied our methodology to a dataset acquired by Petroleum Development of Oman in the Sultanate of Oman. The S-wave velocity model obtained can be easily correlated to surface data, satellite map and time-reflectivity volume; hence demonstrating the potential of our method to build reliable and geologically consistent near-surface velocity models.

An incorrect anisotropy in the Full Wave Inversion (FWI) velocity model leads to imperfect Common Image Gather (CIG) flatness. The main difficulty in the anisotropy estimation through FWI is the strong coupling with velocity. While FWI jointly updating velocity and anisotropy has been proposed, there is evidence that the long wavelength components of the velocity and anisotropic parameters cannot be reasonably decoupled inverting surface data only. The reason is that the long wavelength components of the velocity model inverted by FWI are mainly recovered from the kinematics of diving waves, while decoupling can only be done considering in addition the kinematics of reflected waves. To solve this challenge, we propose an innovative workflow involving joint reflection and diving wave tomography. To overcome the difficulty of first break picking, we propose a robust estimation of first arrival traveltime using the inverted FWI model of the first pass. With the application of this novelty on deep-water data from offshore Africa, we elaborate further with a sequence of first arrival modeling after tuned repositioning of sources and receivers at the sea floor.

Standard reflection-based model building for land applications is challenging due to reduced data quality, near-surface heterogeneities, and the low-fold of reflection data at shallow depths. Broadband and large offset data acquisitions have been developed with the aim of investigating full waveform inversion (FWI) as an alternative tool for velocity model building. FWI using minimally-processed refractions and diving rays provides an efficient solution to recover longer spatial wavelength details in the velocity model. In recent studies this method has been proposed as a means to guide and enhance standard reflection-based methods. Rather than follow refraction/diving ray FWI with reflection tomography, we apply FWI to conventionally-processed reflection data, and move to higher frequencies (up to 13Hz). By incorporating reflection data and higher frequencies we obtain higher resolution structural details such as channels and fault structures and obtain improved imaging results compared to those found by migration velocity analysis. We outline a refraction data preprocessing sequence tailored for data quality at low frequencies and long offsets, and describe the FWI workflow which uses both refractions/diving rays and conventionally-processed reflections. We show the resolution uplift over refraction-based FWI and compare migrated stacks generated with the standard tomography model to that generated with the high frequency FWI result.

In this paper, we discuss the deblending result of a penta-source marine towed streamer data. The small dithering time renders the cross-talk noise to be semi-coherent in all domains, making this dataset challenging for existing deblending techniques. To tackle this data, we propose a new model-based deblending scheme (MBD) which supplements the previously proposed deblending scheme.

3D elastic modelling was performed to compare two acquisition designs . Blind full processing sequence was applied to ensure unbiased conclusions and final quality. Final quality on stack sections are similar in quality for both flat and highly structured sub-surface. some major advantages of carpet recording shall be mentioned: computation cost savings for feasibility studies, the use of a coherent geophysical unit (one shot point), compared to a cross spread (an aggregate of several different shots) may lead to easier preprocessing sequence, shot points can be migrated independently, and working with shot points allow thus real time imaging, impossible with cross spread design.

Full-waveform inversion (FWI) has become the centerpiece of velocity model building (VMB) in seismic processing in recent years. It has proven to significantly improve the velocity model, and thus the migration image, for different acquisition types and different geologic settings, including very complex environments such as salt. With the advent of FWI Imaging, which shows remarkable uplifts over conventional imaging approaches because of the inherent least-squares data-fitting process and the utilization of full-wavefield data, FWI further extends its applications from VMB into imaging. However, FWI applications in the industry as of now prevalently employ the acoustic approximation. While the acoustic approximation can sufficiently explain a majority of the recorded seismic data, thus enabling acoustic FWI to derive reasonable velocity models, its limitation manifests itself around strong impedance contrasts where the elastic effect is strong. For example, at the salt-sediment interface, acoustic FWI (A-FWI) almost always leads to apparent salt halos in the resulting velocity models. With synthetic and field data examples, we demonstrate that the salt halo is mainly caused by the large data mismatch between the elastic input data and the acoustic modeled data in acoustic FWI, particularly at middle to long offsets. Therefore, we developed an elastic FWI (E-FWI) algorithm that combines an elastic modeling engine with the time-lag cost function, which we call elastic Time-lag FWI (E-TLFWI). With a more accurate modeling engine, E-TLFWI can significantly reduce the salt halo observed in its acoustic counterpart. Nevertheless, the migration images using the acoustic and elastic FWI velocity models remain similar overall, with some slight improvements around and beneath salt boundaries, particularly near steep salt flanks, as a result of the reduced salt halo. By contrast, FWI Images derived from E-TLFWI show considerable benefits over those from acoustic Time-lag FWI (A-TLFWI), such as improved event focusing, better structural continuity, and higher signal-to-noise ratio (S/N). The sharpened salt boundaries and enhanced quality of the FWI Images justify the value of elastic FWI.

Difficulties in processing land seismic data often arise due to insufficient sampling of the wavefield. Fully unconstrained simultaneous shooting offers a way to substantially increase productivity and hence source densities, leading to improved sampling of the wavefield. In order to achieve this we must be able to separate the signal from the interference noise. Using a de-blending routine based on inverse problems in the curvelet domain (Guillouet et al., 2016) the following case study from The Sultanate of Oman demonstrates the benefits of dense source sampling for broadband, wide-azimuth land data acquired using simultaneous shooting.