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First EAGE Workshop on Borehole Geophysics
- Conference date: 16 Jan 2011 - 20 Jan 2011
- Location: Instanbul, Turkey
- ISBN: 978-90-73781-95-5
- Published: 16 January 2011
41 - 44 of 44 results
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Characterization of an Uranium Deposit by 3D Borehole Seismic Techniques
More LessThe Millennium uranium deposit is located within the Athabasca Basin of Saskatchewan, Canada. The deposit, situated in metapelitic basement rocks, is controlled by multiple sub-vertical faults, and cross-faults and is overlain by ~500 m of intensely altered, porous Manitou Falls group sandstones. The rock quality directly surrounding the deposit is greatly reduced because of alteration and post Athabasca sandstone structures, which provide conduits for the migration of basin and meteoric fluids. This leads to significant risk for mine development and shaft sinking, because of the increased potential for water inflow into mine workings. To mitigate the risk involved with mining in such complex geology several projects were proposed as part of a pre-feasibility study. Of these, seismic methods were identified as the best tool to potentially identify alteration and structurally compromised zones. Subsequently, a comprehensive surface and borehole seismic program was completed in attempt to delineate these engineering hazards and to provide assurance of success of the shaft sinking and mine development. High resolution 3D, moving source profiling (MSP), vertical seismic profiling (VSP) and borehole side-scans were used at Millennium and their results were integrated, together with geological borehole logs into a comprehensive structural site model.
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Fiber Optic Geophones for Oil and Gas Field Applications
More LessAuthors B.N.P Paulsson, J.K. Andersen, E. Majer and P. HarbenWe are presenting a new fiber optic sensor system implemented as a Fiber Optic Geophone (FOG). We are presenting the design and experimental test results for the FOG and compare its performance with regular exploration geophones and geophones used for scientific investigations. We will demonstrate that the new Fiber Optic Geophone (FOG) has a significantly better performance than the current state of the art coil geophones in terms of noise floor, sensitivity and frequency response.
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VSP Imaging by Wave-field Extrapolation Technique
More LessAuthors B. El Marhfoul, J. Owusu and R. Al-ZayerImaging of Vertical Seismic Profile (VSP) data is routinely performed using Pre-stack Depth Migration (PSDM) processing. This approach requires an accurate subsurface velocity model, which is not always available, particularly in complex geological environments. In this work, we present a procedure to accurately image the subsurface by using common image gathers to update the velocity model. Using a wave-field extrapolation technique, the up-going and the down-going wave-fields from the VSP data are converted into a pseudo surface seismic dataset, while preserving the relative amplitudes and fidelity of the VSP data. Once transformed to the surface domain, the whole range of surface seismic imaging algorithms can be utilized to produce a more accurate subsurface image. Synthetic and real walk-away VSP data examples have shown significant improvements in the imaging quality when wave-field extrapolation is used compared to regular VSP data processing techniques. This technology will help to exploit the full potential of the VSP data.
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A 3D VSP Recorded in Abu Dhabi Yields New Understanding of a Complex Reservoir
More LessAuthors B.N.P. Paulsson, K.W. Müller, W.L. Soroka, S. Marmash, M. Al Baloushi and O. Al JeelaniA two well 3D VSP pilot project recorded in 2007 by the Abu Dhabi Company for Onshore Oil Operations (ADCO) was successful at demonstrating the value that can be gained from a high quality 3D VSP image. This second part focuses on interpretation and value addition. It is understood that for recovery to be optimized and by-passed resources to be minimized especially in later stages of field production more accurate models of a reservoir’s architecture and characteristics are needed. The results of this first 3D VSP survey was successful in characterizing details of the reservoir that could not be derived from the surface seismic or well log data alone. The higher quality images made it possible to map detailed stratigraphy and previously unknown important faults. The improved structural map and updated geologic model generated with information from the 3D VSP images were verified by wells drilled inside the 3D VSP image areas. Based on the successful results from this pilot project the 3D VSP technology is now considered a tool for projects that require detailed reservoir characterization in an area around a well within a diameter equal to the image depth, in this case 3,000 m.
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