Anisotropic velocity model building and depth-imaging for geosteering of extended reach drill ing wells

摘要

We present a case study of geosteering extended reach drilling (ERD) wells into a reservoir using the results of anisotropic velocity model building with tomography and anisotropic depth imaging. Three ERD wells were drilled between September 2004 and June 2005 from a production platform on the Nkossa South structure (Congo) for a satellite field development. The design and the accurate geosteering of ERD wells in a structurally complex area is not an easy task. By geosteering we mean directing deviated wells into a reservoir and keeping them within the reservoir layer (Sheriff, 2002). Before drilling, the structural uncertainty has to be accounted for designing a robust trajectory.