Vertical seismic profiling using a daisy‐chained deployment of fibre‐optic cables in four wells simultaneously – Case study at the Ketzin carbon dioxide storage site

Abstract

The geological storage of carbon dioxide is considered as one of the measures to reduce greenhouse gas emissions and to mitigate global warming. Operators of storage sites are required to demonstrate safe containment and stable behaviour of the storage complex that is achieved by geophysical and geochemical monitoring, combined with reservoir simulations. For site characterization, as well as for imaging the carbon dioxide plume in the reservoir complex and detecting potential leakage, surface and surface‐borehole time‐lapse seismic monitoring surveys are the most widespread and established tools. At the Ketzin pilot site for carbon dioxide storage, permanently installed fibre‐optic cables, initially deployed for distributed temperature sensing, were used as seismic receiver arrays, demonstrating their ability to provide high‐resolution images of the storage formation. A vertical seismic profiling experiment was acquired using 23 source point locations and the daisy‐chained deployment of a fibre‐optic cable in four wells as a receiver array. The data were used to generate a 3D vertical seismic profiling cube, complementing the large‐scale 3D surface seismic measurements by a high resolution image of the reservoir close to the injection well. Stacking long vibro‐sweeps at each source location resulted in vertical seismic profiling shot gathers characterized by a signal‐to‐noise ratio similar to gathers acquired using geophones. A detailed data analysis shows strong dependency of data quality on borehole conditions with significantly better signal‐to‐noise ratio in regions with good coupling conditions.

Wireline distributed acoustic sensing allows 4.2 km deep vertical seismic profiling of the Rotliegend 150 °C geothermal reservoir in the North German Basin

“…This method is based on optical time-domain reflectometry and enables us to register strain changes along optical sensor cables with high spatial and temporal resolution (Parker et al, 2014). Within recent years, a growing number of VSP surveys have been reported, where the DAS method has successfully been applied using sensor cables permanently installed behind casing or along tubing (e.g., Mestayer et al, 2011;Daley et al, 2013;Götz et al, 2018). This deployment method is very convenient as it allows for data acquisition without well intervention.…”

A Review of CO2 Storage in View of Safety and Cost-Effectiveness

“…Apart from conventional surface seismic acquisition, the hydrophone arrays, buried geophone, and the fiber optic cables are permanently installed in the vertical seismic profiling systems to achieve long-term monitoring and obtain the geological structure details [152]. This monitoring technology has been successfully used in the Ketzin pilot site and the MRCSP project.…”

Fiber Optic Distributed Strain Sensing for Seismic Applications

“…For downhole installations, several studies were performed to evaluate the potential of Vertical Seismic Profiling, by Rector and Mangriotis surveys. Generally, it has been shown that although fiber optic data has a lower signal to noise ratio compared to conventional borehole seismic sensors, the higher spatial resolution allows to acquire high resolution exploration results (e.g., Mestayer et al 2011;Cox et al 2012;Daley et al 2013;Götz et al 2018).…”