Workreport 2016-58



Geophysical Logging and Imaging of Drillholes OL-KR56, OL-KR57 and OL-KR57B at Olkiluoto in 2012-2015


Tiensuu, K., Heikkinen, E., Ravimo, I., Kiuru, R.



Page count:



Geophysical logging and imaging were conducted in drillholes OL-KR56, OL-KR57 and OL-KR57B during 2012 – 2015. Drillhole OL-KR56 is 1200 m, OL-KR57 400 m and OL-KR57B 45 m long. Measurements were done by Suomen Malmi Oy. Quality control, processing and reporting were carried out by Pöyry Finland Oy. This report describes the measurements, data processing and results.

Measurements included optical and acoustic imaging and geophysical logging of natural gamma radiation, gamma-gamma density, magnetic susceptibility, dual laterolog resistivity, full waveform sonic, mechanic caliper and fluid resistivity and temperature. Data processing included depth matching to core logging, orienting of images and computing of caliper from acoustic imaging data. Processing of geophysical data included calculating physical properties, presenting natural gamma, gamma-gamma density, susceptibility and resistivity. P and S wave velocities and amplitudes, tubewave energies and waveform attenuations were computed. Rock mechanic parameters were computed.

Acoustic televiewer images showed indications of breakout features in OL-KR56. Acoustic imaging was repeated in order to monitor possible changes in drillhole wall. Significant changes were not observed in two years period. Mechanic caliper and caliper from acoustic imaging provide comparable results, though acoustic televiewer produced caliper is more sensitive and accurate.

A two-channel and a four-channel full waveform sonic probes and interpretation of their data were compared in OL-KR56. Interpretation provided comparable results both with first arrival picking (two-channel data) and semblance analysis (four-channel). Semblance analysis can produce more reliable velocity data when petrophysical velocity reference is not available, and fluid velocity cannot be approximated with constant value.

Resistivity logging using normal array was measured in OL-KR56 to compare normal array and focused laterolog resistivities. Both methods provide similar general level of resistivity when normal resistivity is corrected for fluid resistivity. Focused dual laterolog requires drillhole fluid correction only at very low fluid resistivities.


Geophysics, drillhole logging, drillhole imaging, bedrock characterization, spent nuclear fuel disposal, method comparison, full waveform sonic, resistivity, caliper.


Geophysical Logging and Imaging of Drillholes OL-KR56, OL-KR57 and OL-KR57B at Olkiluoto in 2012-2015 (pdf) (2 MB)


Share article: