Successful sidetracking of a well onshore Germany by integration of 3D vertical seismic profiling technology – a case study |
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| Authors: | S Frehers F Ogliani G Rüth T Ter Burg |
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| Institution: | 1. RWE Dea, überseering 40, 22297 Hamburg, Germany;2. Schlumberger, via dell’Unione Europea 4, 20097 San Donato Milanese, Milan, Italy;3. Schlumberger, Parkstraat 83‐89, 2514 JG The Hague, The Netherlands |
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| Abstract: | The exploration for and exploitation of deep Lower Rotliegend gasfields onshore in North Germany often suffers from poor surface seismic imaging. This is owing to the depth of the reservoirs and a thick and complex Zechstein salt overburden. RWE Dea conducted a 3D vertical seismic profile (VSP) survey in a low‐performing production well after the borehole was plugged near total depth. Our main objective was to improve the seismic image of the reservoir zone in the vicinity of the well to determine a new landing point for a planned sidetrack. Because acquisition was in a densely populated and also partially environmentally protected area, there were surface restrictions concerning source deployment. Additionally, due to the complex geological setting, we conducted two 2D VSP field tests and thorough pre‐survey modelling to achieve the best results in terms of seismic imaging, environmental impact and reasonable cost. Deformation bands in the drill core suggest that the initial well was drilled close to a major fault, which was regarded as the main reason for the disappointing production rate. Therefore, we put special emphasis on fault detection in our processing and interpretation. Our interpretation approach used an enhanced structural mapping workflow that helped to design a sidetrack. When the sidetrack was drilled two years later, it ended up being one of the most productive wells in the field. |
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| Keywords: | VSP Borehole geophysics Acquisition Data processing Modelling |
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