Workreport 2011-85

Fracture-Specific Pressure Measurements at the Olkiluoto Site in Eurajoki, Drillhole OL-KR39

Ripatti, K., Pöllänen, J., Hurmerinta, E. & Rouhiainen, P.

English

27

An option was built to the Posiva Flow Log, Difference flow method (PFL DIFF). A double packer device was combined together with a PFL DIFF probe. The new tool was needed for measurements of the very low hydraulic head. Indications of these were detected earlier in some fractures of drillhole OL-KR39. The target fractures could be measured with the accurate absolute pressure sensor in the PFL DIFF probe. Principles of the methods and the results of measurements are presented in this report. The measurements were carried out in drillhole OL-KR39 at the Olkiluoto investigation site between April 2011 and May 2011.

The device used includes a sensor for single point resistance (SPR). SPR measurement is used to place the device accurately on the chosen fracture. The section length limited by the packers is about 1 m.

The measurements were carried out in natural (i.e. un-pumped) conditions. The same measuring program was employed in all chosen fractures.

Electrical conductivity (EC) of drillhole water and flow rate along the drillhole were also measured in conjunction with the pressure measurements.

Groundwater, pressure, measurement, bedrock, drillhole, Posiva Flow Log.

Fracture-Specific Pressure Measurements at the Olkiluoto Site in Eurajoki, Drillhole OL-KR39 (pdf) (1.3 MB)