Summary
NGU has carried out borehole logging in well LYB CO2 Dh4, in Adventdalen 5 km outside Longyearbyen. The well was drilled to locate deep sandstone formations that may be used to store CO2. The project "Longyearbyen CO2 Lab" of UNIS and partners, will use the test site as laboratory for injection, storing and monitoring CO2 in the underground. The well was drilled full coring telescope operation to 970 m and was successful in that it cored Late Triassic sandstones that also show injectivity.
Logging parameters were temperature, fluid conductivity, natural gamma, rock resistivity, seismic velocity, caliper, relative density and borehole deviation. The well was also inspected by acoustic televiewer to map fractures. Because of a cased wellbore and the small borehole diameter in the deepest part, the entire borehole could not be logged.
The results show good correlation between the geophysical logs and the lithological units. Sandstones are indicated with low gamma radiation and increasing seismic velocity and apparent resistivity. Acoustic televiewer interpretation shows that some of the sandstones are highly fractured, which is confirmed by lowered seismic velocity and resistivity. Cap rock silt- and mudstones are fractured but the fractures do not influence strongly on the seismic velocity and resistivity log. In sum, this might indicate that the fractures in the sandy layers are open and water filled, whereas fractured siltstone is tight.
