SG-3 well reaches unexpected depth

At 12,262 meters beneath the Kola Peninsula, the SG-3 well recorded temperatures of 180 °C, much higher than the 100 °C predicted by geophysical models at that depth.

Unusual rock behavior at depth

The rocks at that depth behaved like soft plastic instead of hardening, which surprised scientists. This unexpected behavior was due to the high temperature and pressure found at such a depth.

Origins of the SG-3 project

The SG-3 well was part of a Soviet project launched in 1970 to explore the continental crust, driven by scientific rivalry with the United States. The goal was to drill 15,000 meters, but the project stopped short by 2,738 meters.

Achievements and challenges

The SG-3 well reached 12,262 meters in 1989, a depth that has never been matched. It gained 2,679 meters in a decade, or about 268 meters per year, despite challenges such as broken equipment and difficult conditions.

Physical conditions at the well's depth

The temperature at the bottom of the SG-3 well was 180 °C, accompanied by immense pressure of about 2.7 tons per square centimeter. These conditions made the rock ductile and viscous, affecting drilling operations and equipment reliability.

Scientific findings and surprises

The well revealed fractured rocks, water at several kilometers depth, microfossils, and geological layers that did not match seismic models. These findings deviated from initial predictions and provided new insights into the Earth's crust.

Project termination and context

The SG-3 project was halted in 1992, partly due to the post-Soviet crisis and partly due to the extreme conditions at depth. The site was officially closed in 1995, ending a significant chapter in geological exploration.

Legacy of the SG-3 well

Despite the challenges, the SG-3 well remains the deepest vertical well ever drilled, with a depth of 12,262 meters. Its legacy includes both scientific discoveries and the recognition of the complex factors that ended the project.