VSP measurements used as a tool for improving seismic sub-salt imaging in brownfield development

Abstract

Many of the Paleozoic Rotliegend low-permeability dry gas fields in the Southern Permian Basin of northern Germany are covered by Mesozoic salt dome structures. The resulting complexity in the overburden leads to imaging problems in subsalt reservoirs typically situated at depths between 4000 m to 5000 m TVD. Since structural compartmentalization is often the key challenge in field development, good resolution seismic is essential for well planning. For the study area, only a vintage 3D seismic survey from 1993/94 with limited data quality exists. Acquisition of new 3D seismic data is not possible owing to permitting restrictions and public resistance. Therefore the focus is on the acquisition of 2D VSPs in every new drilled well. The VSP measurements give local insights into the reservoir in the vicinity of the wellbore. With a general structural understanding and production history in mind, those local insights generate immense value for the understanding of the field.