P8.8 - Application of Distributed Optical Fiber Sensors to Borehole Temperature and Strain Monitoring
- SENSOR+TEST Conferences 2011
2011-06-07 - 2011-06-09
- Proceedings SENSOR 2011
- P8 - Mechanical
- N. Nöther, M. Krcmar, S. von der Mark - BAM Bundesanstalt für Materialforschung und –prüfung, Berlin (Germany), J. Henninges - Helmholtz Centre Potsdam (Germany)
- 874 - 877
We report on the successful application of distributed optical fiber sensors for temperature and strain measurement into a borehole. Fiber sensors have been installed at the outside of the well casings to a depth of 800 m. Continuous, truly distributed strain and temperature measurements were performed during a 5-day cycle of operational temperature changes within the well.
For distributed strain measurement, a novel approach to Brillouin sensing was employed, comprising an all-digital sensing configuration in the frequency domain (BOFDA: Brillouin optical frequency domain analysis). This novel instrumentation was used to record a continuous profile of mechanical strain of the optical fiber, integrated into the well in a loop configuration with a total length of 1650 m. The BOFDA measurement was referenced to a classic distributed Brillouin measurement (BOTDA: Brillouin optical time domain reflectometry); additionally, distributed temperature measurements were performed by means of Raman DTS.
This measurement campaign demonstrates the feasibility of Brillouin and Raman sensing for borehole monitoring and introduces the alldigital BOFDA technique as a promising alternative to conventional BOTDA sensing systems. Strain monitoring in boreholes could yield important information about mechanical loads and the integrity of the completion of wells used for production of oil and gas or geothermal energy, as well as the geologic storage of CO2.