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Making informed field development decisions requires taking uncertainty into account. Geostatistical inversion is a key technology for quantifying uncertainties using available seismic and well data. However, the common practice, consisting of choosing the "best possible" parameters, results in unrealistically small uncertainty estimates. In this paper, we propose a multi-scenario approach to geostatistical inversion. By considering various alternative scenarios, a more realistic picture of the overall uncertainty can be built. This is illustrated on a case study, where the traditional single-scenario practice and the proposed multi-scenario approach are compared.

The size and complexity of the mega gas clouds in offshore Brunei pose severe imaging problems to the structures underneath. We present a comprehensive technical package to tackle the complex wave propagation and anelastic energy losses associated with these gas clouds. We started by running FWI to resolve the velocity of the shallow gas clouds, followed by reflection tomography. We then conducted FWI-guided Q tomography to obtain high-resolution absorption model. For the deep gas clouds, since their depth and the incurred low signal-to-noise ratio in the CMP gathers are beyond the limit of these geophysical methods, we moved on with geologically-guided scenario testing in intense collaboration with geologists. Finally, we carried out visco-acoustic TTI reverse time migration (Q TTI RTM) to better deal with the issues of multi-pathing and strong attenuation. This complete package brings significant uplift to the image as compared to the vintage QPSDM result, and therefore can serve as an effective option before turning to C-wave imaging.

Recent discoveries in the Pil and Bue prospects, targeting Melke and Rogn Formation sandstones on the footwall of the Vingleia Fault complex, have rejuvenated interest in exploration around the Frøya High region. The wildcat well, 6406/12-3 S (Pil 1), with estimated resources of 8.8-21.1 MMSCM, has focused current attention on combined structural-stratigraphic traps associated with proximal rift sedimentation, restricted to the eastern margins of the Southwest Basin, Halten Terrace. This study provides an integrated reservoir quality assessment of the Late Jurassic Viking Group in the Frøya High region, focusing on sand distribution and reservoir quality.

This paper focusses on improving the seismic image on a dataset from offshore Trinidad; Tobago by using full-waveform inversion (FWI) to refine the shallow velocities and also describes geological information that can be inferred directly from the resulting velocity model. In the first half of the paper the geology of the region is introduced, then the imaging issues, before describing the FWI methodology and results. The second half of the paper discusses interpretational aspects of the FWI velocity model and highlights its use in a blind pore pressure prediction (PPP) test of well data.

Deblending procedure for dense land/OBC/OBN acquisition based on sparsity promoted inverse problem. A general formulation for simulatneous source acquisitions is used to recover data from highly blended acqusition. This procedure uses cutting-edge mathematical tools from Compressed Sensing theory like l1-regularized inverse problem in the curvelet domain to acheive unprecedented deblending results.

Using full-waveform inversion (FWI) to update velocity models that contain salt bodies with high velocity contrasts is challenging. It is even harder if erroneous salt geometry is part of the velocity model. Shen et al. (2017) showed a successful FWI application that corrected some misinterpretation of salt structures and resulted in improved subsalt images at the Atlantis field in the Gulf of Mexico. Their study stressed the importance of the low frequencies (usable down to 1.6 Hz), full azimuths, and wide offsets of OBN data. Encouraged by the success at Atlantis, we revisited some aspects of FWI algorithms to minimize cycle skipping and amplitude discrepancy issues that are common in the presence of salt and salt misinterpretation. Here we present the use of travel time misfit measured in frequency-dependent time windows as the FWI cost function. It is devised to minimize the negative impact from the amplitude discrepancy and cycle-skipping between the recorded data and modeled synthetic data. Furthermore, we use the crosscorrelation coefficient between the recorded data and shifted synthetic data as a weight function in gradient computation to promote travel time measurements of higher quality. We demonstrate the effect of our approach using a staggered full-azimuth streamer data set in an area of complex shallow salt bodies in the Gulf of Mexico.

Imaged based Q-compensation coupled with FWI can solve for significant frequency and amplitude losses below shallow overburden absorptive geologic bodies. Applying Q-compensation to both the baseline and monitor 4D surveys improves the consistency of the 4D response, leading to more reliable placement of development wells. This should lead to enhanced production and improved reservoir management.

In this paper we demonstrate the ability of acoustic land FWI to recover a high-resolution velocity model using reflected waves in addition to diving waves and inverting up to 13 Hz.

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.