East Flanders

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East Flanders

Acquiring Shear-wave Information In Shallow-water Environment From Field Data Near Ghent, Belgium

Versteeg, Willem (Ghent University) | el Allouche, Nihed (Delft University of Technology) | Thorbecke, Jan W. (Delft University of Technology) | Ghose, Ranajit (Delft University of Technology) | Drijkoningen, Guy G. (Delft University of Technology)

OnePetroNovember, 2008

Summary A multi-component seismic experiment was conducted by deploying a 4-C ocean-bottom cable in a shallow water canal. The aim of the experiment was to investigate the feasibility of acquiring shear-wave information in shallow marine environment. In the recorded data, we observe airgun generated shear-wave reflections. This observation is validated by a model study. The presence of shear-wave reflection is caused by the low frequency of the source in relation to the water depth. Furthermore, converted waves have also been identified based on two "attributes" namely the particle polarization and the normal moveout velocity. Comparison with synthetic data suggests the presence of waves converted at a reflector as well as at the water bottom. Introduction Shear-wave information is often necessary for the characterization of the shallow subsurface and for the retrieval of geotechnical parameters. During the last three decades, it has been shown by many that the S-wave velocity is much more sensitive to changes in lithology and mechanical properties than the P-wave velocity. In marine setting, the S-wave information can be obtained from seismic measurements. Different methods exist towards this end. Gerhmann et al. (1984) developed a system which directly generates and records horizontally polarised Swaves in shallow water areas. The system consists of a modified airgun capable of generating horizontal shear stress and a 3-component geophone system placed at the water bottom. The authors showed an example of marine shear-wave refraction profiling in the Baltic Sea. Although this system proved to be useful, it is has not been much used. For structural mapping P-waves are still the most successful in marine environment. Therefore people have been inverting for the S-wave velocity from PP-reflections. However, Riedel et al. (2001) showed that large uncertainties are involved in the estimation of the S-wave velocity. These uncertainties are attributed to the insensitivity of the P-wave reflection amplitude to this parameter in shallow marine sediments. Another approach to obtain S-wave information has been proposed by Caiti et al. (1994) and it involves recording surface waves using a receiver array laid down on the water bottom sediments. The recorded surface waves are analysed and inverted to obtain S-wave profiles (Caiti et al. 1994 and Park et al., 2000). However, the depth of these profiles is limited and the accuracy and resolution are depthdependent. The S-wave velocity can also be retrieved from converted waves i.e., waves converted from compressional to shear mode. In hydrocarbon exploration, these waves have been applied successfully for many years. For shallow marine environment, modeling studies showed that there are two angles where maximum S-wave conversion can be expected (el Allouche et al. 2008), one at moderate angles (between 40 and 50 degrees) and one at post-critical angels. An appropriate way to detect converted waves is to use an ocean-bottom cable configuration. In this abstract, we show the results of a multi-component seismic experiment conducted by deploying a 4-C oceanbottom cable in a shallow water canal. An analysis of the components suggests the presence of source generated shear-waves as well as converted waves in the data.

OnePetro

SEG

SEG-2008-1278

2008 SEG Annual Meeting

Country: Europe > Belgium > Flanders > East Flanders > Ghent (0.40)

Geophysics:

Geophysics > Seismic Surveying > Seismic Processing (1.00)
Geophysics > Seismic Surveying > Seismic Modeling > Velocity Modeling (0.51)

Industry: Energy > Oil & Gas > Upstream (1.00)

SPE Disciplines: Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)

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[20]P1 New Simulators for Catalytic Reforming Processes

Galtier, P. (Institut Français du Pétrole, France) | Vacher, Ph (Institut Français du Pétrole, France) | Froment, G. (Rijksuniversiteit Gent, Belgium)

OnePetroOctober, 1997

Abstract. Operator training, as well as process automation and optimization, are based on increasingly precise and comprehensive simulations of plant operations. For catalytic reforming, a key process for gasoline production, it is now possible to develop unit simulators based on advanced kinetic models of complex mixtures. For process development and design, more predictive kinetic models are needed to replace the usual correlative approaches. The model is based on molecular kinetics. The rate expressions are of the Langmuir-Hinselwood type. The reactor effluent and feed compositions are described by a set of 39 pseudo-components. This model has been validated through pilot and industrial runs. For operator training and unit operation, we have developed process simulators for the entire unit either in steady state or in dynamic mode. The intrinsic kinetic model for reactors provides high fidelity representation of the unit behaviour. Such a simulator has been running since 1994 for operator training at the Elf-Donges refinery. The advantage of this approach is to use the same basic modelling throughout the process life-cycle. INTRODUCTION Modelling and simulation are used all along the process life-cycle, namely: development, design, operator training, unit operation monitoring, advanced process control, optimisation. Previously, the variety of goals of the simulation has led to numerous types of models and simulators for the same process at different steps of its life-cycle. Moreover, these models and simulators were developed, often with no links between them. Modelling and simulation have been drastically moved forward these later years: - By the ‘technology push’: fast increase in computational power, new software development, - By the ‘end-user pull’: refiners are asking for more automation and optimisation of their plants; process development and design staff within R&D centres need accurate models to improve the quality of the unit's design and to provide refiners with safe and productive plants. The requirements of the various end-users are now converging towards high-fidelity modelling. As the computer tools are available to satisfy these requirements, it is now possible to use the same basic highfidelity modelling for all types of simulation and control of a given process. KINETIC MODELLING IFP has developed such high fidelity models for catalytic reforming, a key process for gasoline production. The model has been first studied and developed by the team of Professor G. Froment in the Laboratorium voor Petrochemische Techniek of the Rijksuniversiteit (Gent, Belgium). The model was then adapted to the specific needs of IFP and validated by

OnePetro

WPC

WPC-29300

15th World Petroleum Congress