Abstract
Because zero-offset VSP (Vertical Seismic Profile) data can only provide the information of rock properties and structure in the area around the Fresnel zone within the well, the scheme of VSP with offset was developed to acquire the reflection information away from the borehole in order to widen the range of VSP survey and to improve the precision of imaging.
In this paper, we present a new CDP (Common Depth Point) mapping approach to image the reflecting structure by using offset VSP data. For the processing of offset VSP data, we firstly separated the up-going and down-going wave-fields from VSP data by means of F-K filtering technique, and we can calculate the mapping conditions (position and reflecting traveltime for CDP point) in homogeneous media, and then reconstruct the inner structure of the earth.
This method is tested by using the offset VSP data which are used to simulate the case of super-deep borehole by means of finite-difference method. The imaged structure matches the real model very well. The results show that the method present here could accurately image the inner structure of the earth if the deviation of initial velocity model from the true model is less than 10%. Finally, we presented the imaged results for the real offset data by using this method.
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This work is supported by the foundation of President of Chinese Academy of Sciences.
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Chen, JY., Zhang, ZJ., Wang, GJ. et al. CDP mapping and image reconstruction by using offset VSP data. Acta Seimol. Sin. 13, 98–104 (2000). https://doi.org/10.1007/s11589-000-0087-7
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DOI: https://doi.org/10.1007/s11589-000-0087-7