Application of Geophysical Technologies and the Impact on Shell

Abstract

Abstract The application of a wide range of geophysical technologies (ranging from Narrow-Azimuth (NAZ), Wide-Azimuth (WAZ) streamer and Ocean-Bottom-Seismic (OBS) node acquisition, to anisotropic seismic imaging) has resulted in considerable business impact on Shell's GOM field development. In this paper, results will be shown for several GOM deepwater fields. Introduction Whereas seismic processing for large Gulf of Mexico (GOM) exploration projects typically focuses on imaging the unseen (often imaging below complex salt structures), seismic processing for development projects often has to focus on adding further fine detail to the seismic data. Typical business drivers demanding such details for development are:–Well-Positioning requiring enhanced lateral and vertical positioning–Reservoir Modeling requiring enhanced seismic resolution to enhance stratigraphic details–Reservoir monitoring requiring time-lapse signal To address these challenges, respectively, a variety of seismic processing techniques like anisotropic velocity model building + PreStackDepthMigration (PreSDM), High Definition Seismic imaging, and 4D TimeLapse processing are commonly applied in our development projects. Hereby, various seismic acquisition methods are used (ranging from Narrow-Azimuth (NAZ), and Wide-Azimuth (WAZ) streamer, to WAZ Ocean-Bottom-Seismic (OBS) node acquisition). The application of all these geophysical technologies has resulted in considerable business impact on Shell's GOM field development. In this paper, results will be shown for several GOM deepwater fields. Geophysical Technologies Anisotropy and Pre-Stack Migration Anisotropy impacts the positioning and focusing of subsurface events. Taking anisotropy properly into account in PreSDM can significantly reduce subsurface uncertainties, improve the seismic to well match, and impact well positioning. In the GOM with its many salt structures embedded in sediments, we especially recognize the effect of differential anisotropy: isotropic salt bodies next to anisotropic sediments. This can easily lead to false structures next to and below salt. The typical velocity model building procedure used here has been described in detail by Stopin et al. (2008) and consists of several migration and update cycles where the velocity and the anisotropy parameters (d and (or ?)) are inverted for. Final acceptance criteria are PreSDM results with flat image gathers and small seismic to well misties (typically not more than 100 ft). It should be noted that this anisotropic velocity model updating procedure is a highly integrated iterative effort involving processing, interpretation, and well-positioning staff.