Looking into Geological History

A 2,5 km deep borehole was drilled in Åre (Sweden) with the purpose of understanding how major mountain belts of Alpine-Himalayan dimensions developed over a period of 500 million years. CMR’s part in the project was to provide advanced fibreoptic distributed temperature sensing.

07.12.2015 by Gunn Janne Myrseth

Looking into Geological History

Photo: CMR’s measurement team on site in Åre (Sweden): Scientist Peter J Thomas (left) and Scientist Stian Husevik Stavland installing blue fibreoptic cable in the 2.5 km deep borehole of COSC-1.

 

CMR has delivered fibreoptic distributed temperature sensing to an international scientific deep drilling project, resulting in an impressive accuracy of 0.1°C and a spatial resolution of less than 0.5 m.  

How?

A 2.5 km deep borehole was drilled in Åre (Sweden) by the scientific drilling project ‘Collisional Orogeny in the Scandinavian Caledonides’ (COSC-1), funded by the International Continental Scientific Drilling Program. The purpose was to understand how major mountain belts of Alpine-Himalayan dimensions developed over a period of 500 million years.

CMR’s part in the project was to perform distributed temperature sensing (DTS) inside the borehole in order to accurately measure the vertical temperature profile. High-resolution and high-accuracy temperature measurements are a key requirement for research on heat flow, hydrogeology and the modelling of past surface temperatures from the borehole temperature profile.

Our approach to the challenge was to develop a low-cost rugged solution based on an off-the-shelf fibreoptic cable with a cost of less than NOK 10 per meter. The measurements were performed in August 2015 and were supplemented by traditional high-cost methods for temperature logging. The average thermal gradient was found to be 20°C/ km while the complete results and scientific analyses will be published in scientific journals in 2016.

Powerful technology

Distributed sensing based on fibreoptics is a powerful technology for highly accurate measurements in harsh and non-accessible environments which can be found in a number of industries (geothermal, carbon capture & storage, oil & gas) and applications (environmental monitoring, traffic surveillance, etc.). The versatility of optical fibre makes it well suited for performing simultaneous measurements of as different parameters as temperature, strain, vibration, acoustics, humidity, salinity, etc. CMR is currently working with and developing fibreoptic measurement technologies within these areas.