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Workreport 1997-17

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Name:

Eurajoen Olkiluodon kairanreikien OL-KR9 ja OL-KR10 geofysikaalisten reikämittausten tuloskäsittely ja rakennemallin tarkistus

Writer:

Kai Front; Olli Okko; Pertti Hassinen

Language:

Finnish

Page count:

106

Summary:

Working report: INTERPRETATION OF GEOPHYSICAL LOGGING OF BOREHOLES OL-
KR9 AND OL-KR10 AT THE OLKILUOTO SITE AT EURAJOKI AND
REVISION OF THE BEDROCK MODEL

Front, K., Okko, O. & Hassinen, P.
VTT/Communities & Infrastructure
Posiva Work Report 97-17

ABSTRACT

The Finnish power companies Teollisuuden Voima Oy and Imatran Voima Oy are
preparing for final disposal of the high-level nuclear fuel waste deep into the bedrock.
The Olkiluoto research site at Eurajoki is one of the four candidates selected for the
detailed site characterization. This report describes the processing and interpretation
of standard single hole geophysical borehole logging carried out in the 600 m long
boreholes KR9 and KR10 cored in 1996 at the Olkiluoto site at Eurajoki.

Furthermore, the structural bedrock model of the Olkiluoto site was reviewed
according to the hydraulic conductivity measurements, and oriented fracture data of
dipmeter, televiewer and borehole-TV applied in the 76 mm diameter hole KR10 as
well as according to the reflections obtained by oriented borehole radar and VSP
surveys.

Lithological units, mica and tonalite gneiss, pegmatite and short amphibolite-like
sections, are classified by the use of combined natural gamma radiation, density and
magnetic susceptibility information. Fracturing is analysed by the interpretation of
different types of acoustic, density, resistivity and temperature logs. There are
typically 1 - 3 fractures per meter in the drilled borehole cores. Fractures are
commonly filled with kaolinite, carbonate, illite or sulphides. Fractured sections are
located and described along each of the boreholes by combining the logs of fluid
temperature and salinity together with the porosity and modulus of elasticity derived
from the full wave form sonic log and the visual observations at the core samples.
According to hydraulic conductivity tests and attenuation of both body and tube waves
in the full vaweform acoustic logs, 3 - 5 individual sections were considered as areally
significant fractured zones. Geometrically, these sections and the adjoining VSP
reflections are rather well compatible with the bedrock model. Thus, the most
hydraulically conductive borehole sections are suggested to be combined as single
large gently dipping major fracture zone. It is typical of this structure to introduce
several meters long geophysical anomalies, but short (< 1m) fractured core sections.
Moreover, the borehole-TV and acoustic televiewer images show only single open
fractures or fracture groups, which have remarkably large apertures.


Key words: Geophysical, structural bedrock model, lithological unit, fracturing,
hydraulic conductivity
INTERPRETATION OF GEOPHYSICAL LOGGING OF BOREHOLES OL-
KR9 AND OL-KR10 AT THE OLKILUOTO SITE AT EURAJOKI AND
REVISION OF THE BEDROCK MODEL

Front, K., Okko, O. & Hassinen, P.
VTT/Communities & Infrastructure
Posiva Work Report 97-17

ABSTRACT

The Finnish power companies Teollisuuden Voima Oy and Imatran Voima Oy are
preparing for final disposal of the high-level nuclear fuel waste deep into the bedrock.
The Olkiluoto research site at Eurajoki is one of the four candidates selected for the
detailed site characterization. This report describes the processing and interpretation
of standard single hole geophysical borehole logging carried out in the 600 m long
boreholes KR9 and KR10 cored in 1996 at the Olkiluoto site at Eurajoki.

Furthermore, the structural bedrock model of the Olkiluoto site was reviewed
according to the hydraulic conductivity measurements, and oriented fracture data of
dipmeter, televiewer and borehole-TV applied in the 76 mm diameter hole KR10 as
well as according to the reflections obtained by oriented borehole radar and VSP
surveys.

Lithological units, mica and tonalite gneiss, pegmatite and short amphibolite-like
sections, are classified by the use of combined natural gamma radiation, density and
magnetic susceptibility information. Fracturing is analysed by the interpretation of
different types of acoustic, density, resistivity and temperature logs. There are
typically 1 - 3 fractures per meter in the drilled borehole cores. Fractures are
commonly filled with kaolinite, carbonate, illite or sulphides. Fractured sections are
located and described along each of the boreholes by combining the logs of fluid
temperature and salinity together with the porosity and modulus of elasticity derived
from the full wave form sonic log and the visual observations at the core samples.
According to hydraulic conductivity tests and attenuation of both body and tube waves
in the full vaweform acoustic logs, 3 - 5 individual sections were considered as areally
significant fractured zones. Geometrically, these sections and the adjoining VSP
reflections are rather well compatible with the bedrock model. Thus, the most
hydraulically conductive borehole sections are suggested to be combined as single
large gently dipping major fracture zone. It is typical of this structure to introduce
several meters long geophysical anomalies, but short (< 1m) fractured core sections.
Moreover, the borehole-TV and acoustic televiewer images show only single open
fractures or fracture groups, which have remarkably large apertures.


Key words: Geophysical, structural bedrock model, lithological unit, fracturing,
hydraulic conductivity

Keywords:

Geofysikaalinen; rakennemalli; kivilaji; rikkonaisuus; vedenjohtavuus

File(s):

Eurajoen Olkiluodon kairanreikien OL-KR9 ja OL-KR10 geofysikaalisten reikämittausten tuloskäsittely ja rakennemallin tarkistus (pdf) (2.9 MB)


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