A case example of near-surface correction for multicomponent VSPS |
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| Authors: | Xinwu Zeng Colin MacBeth |
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| Institution: | Edinburgh Anisotropy Project, British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA, Scotland, UK.;Presently at Department of Applied Physics, Changsha Institute of Technology, Changsha, Hunan, 470073, P.R. of China. |
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| Abstract: | A deterministic near-surface correction procedure is developed for multicomponent VSP data, shot using directional sources and recorded using three-component receivers. The method is capable of removing unwanted effects of acquisition such as unequal source strengths or misorientations, but may also remove near-surface multiples and anisotropy. This is of considerable benefit for obtaining accurate and consistent estimates of subsurface anisotropy from different source combinations. Application of the technique is illustrated using a dataset from the Romashkino reservoir in Russia, where three or four different directional sources are used at the same source locations. The technique corrects for the large discrepancies which exist between the estimates obtained using different source combinations. Application of the technique to three wells in the survey region reveals a nearly isotropic subsurface, except for a few isolated zones of moderate to high (2 to 8%) anisotropy which lie close to the expected depth for the reservoir. Although there is no significant correlation with the production figures for each well, the qS1 polarization azimuth within the reservoir does vary at each well location, suggesting that this may be a more sensitive indicator of reservoir Drocess. |
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