COSC Deep Drilling - fibreoptic temperature measurements
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.
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.
How CMR measured the temperature in a 2.5 km deep bore hole with an accuracy of 0.1°C:
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 which is an important parameter in the geological analyses. 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 DTS measurements were performed in August 2015 and were compared with traditional methods for temperature logging. The measurements showed an average thermal gradient of 20 °C/ km
The complete measurement results and scientific analyses will be published in scientific journals in 2016.
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.
The International Continental Scientific Drilling Program