posiva 2002 22 working report web

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W o r k i n g R e p o r t 2 0 0 2 2 2

Fracture

Maooing from Olkiluoto

Borehole

Image

Data

2001

Eve l i ina

T a m m i s t o

T o m a s

L eh t im ak i

J o r m a

P a l m e n

Pi r jo He l la

Eero H e i k k i n e n

i n t ac t

y

ay

2 0 0 3

Working Reports contain information

on work in

progress

or

pending

completion.

The

conclusions and viewpoints presented in the report

are

those

of

author s)

and

do not necessarily

coincide wi th those of Posiva.


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TEKIJAORGANISAA TIO:

TILAAJA:

Fintact y

Hopeatie 1 B

00440 Helsinki

Posiva Oy

Toolonkatu 4

00100 Helsinki

TILAUSNUMEROT:

Fin tact Oy: 9646/0 1/HH

TILAAJAN YHDYSHENKILO:

Heikki Hinkkanen

Posiva Oy

TEKIJAORGANISAATION YHDYSHENKILO:

TEKIJAT:

TYORAPORTTI 2002-22

FRACTURE MAPPING FROM OLKILUOTO BOREHOLE

IMAGE DATA 2001

Eveliina Tammisto Tomas Lehtimaki Jorma Palmen Pirjo Hella Eero

Heikkinen

TARKASTAJA:

Henry Ahokas

Fintact Oy


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Tammisto, E., Lehtimaki, T., Palmen, J., Hella, P. Heikkinen, E. 2002. Fracture

mapping from Olkiluoto borehole image data, 2001. Working Report 2002-22. Posiva

Oy, Helsinki. 109 p.

BSTR CT

As a part of the complementary site investigations for the underground disposal of spent

nuclear fuel at Olkiluoto site, fracture mapping from optical imaging data was done in

boreholes KR1, KR2, KR4, KR9, KR12, KR13 and KR14. The data contained BIP

imaging, carried out in 1996, from sparsely fractured sections in KR1, KR2 and KR4

that have not been included into previous interpretation (745 m), and OPTV imaging

results from KR9, KR12, KR13 and KR14 in 2001 (2306 m).

The task included fracture mapping from the image material and determination of

orientation of the fractures using the Well CAD utility, determination of properties of the

fractures, compilation

of

print-outs, and data delivery. The following fracture properties

were mapped: fracture type, aperture and filling thickness, fracture shape and colour.

The results of this independent mapping task provide supplementary information, i.e.

complete orientation coverage, apertures, etc. not found from core mapping data. The

observations were checked with comparing them to the core samples.

n total6138 fractures were mapped. These represent roughly 80 of the core mapping

fractures. Not every fracture reported from core can be observed from the images, but

on the other hand, specifically from frequently fractured and core loss sections also few

possible previously non-reported fractures have been encountered.

The open or partly open fractures, some of which might have also filling, make on

average 5

of

all fractures.

In

less fractured

KR1

and KR2 these are rare, and in KR4

and KR13 more frequent (9 ) than for the others. Fractures with filling form two-third

of all fractures, and closed ones one-third. Aperture and thickness both range from 0.5

mm to 120 mm. Thickness has been reported for most

of

the fractures.

More than a h lf of the fractures are planar and smooth in their shape (55 ). Slightly

less (one-fifth) are found both planar and rough, and undulating and smooth. The

fracture colours are determined mostly as a grey scale (60-80 . Black fillings are seen

less than others probably due to dark background, grey and white are more frequent. For

KR2 and KR13 the colours brown, green and yellow are found relatively often.

Seepage has been found from 0 - 49 fractures per borehole, most frequently in KR12.

For almost

h lf

of these seepage locations, a hydraulic conductivity indication has been

found with good depth agreement. Based on seepage, these are potential inflow

locations in open borehole conditions.

Keywords

Borehole optical imaging, fracture interpretation, nuclear waste disposal


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ONTENTS

BSTR CT

TIIVISTELM

CONTENTS

PREF CE

INTRODUCTION 3

2 IMAGE MATERIAL 7

2 1 Image logging arrangements 7

2 2 The image properties 10

2 3 The image quality due

to

borehole conditions

14

2 4 The preconditioning of the image material

23

3 MAPPING THE FRACTURES 25

3 1

Preparation of the material

25

3 2

Picking

of

the features 25

3 3 Quality criteria of the picking

26

4 DETERMINATION OF THE PROPERTIES

31

4 1

Design of property parametres

31

4 2 The distribution of mapping results according to level of confidence

71

5 CHECKING THE OBSERVATIONS WITH THE CORE SAMPLES 73

5 1 The checking procedures 73

5 2

The results

of

the checking

73

6 RESULTS 75

6 1

Contents

of

the results

75

6 2 Fracture type distributions 75

6 3 Fracture aperture

and

thickness 80

6 4 Fracture forms

80

6 5 Fracture filling colours

81

6 6 Inflow indications 83

6 7 Presentation of results

and

data delivery

88

6 8 Comments on results 89

7 SUMMARY

91

REFERENCES 93

APPENDICES

97


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2

PREF CE

This report describes fracture interpretation of borehole imaging data from Olkiluoto in

2 1 (supplementary mapping

of

KRl KR2 and KR4, and mapping of KR9, KR12,

KR13 and KR14). This work belongs to Posiva site characterization programme for

spent nuclear fuel disposal. The work has been ordered from and supervised by Posiva.

The authors wish to thank Posiva s contact persons Mr. Heikki Hinkkanen and Mrs.

Liisa Wikstrom for their useful comments and guidance. We also thank the experts

who reviewed the work and results on their essential communication: Dr. Alan

Geoffrey Milnes

of

GEA Consulting, Dr. John Hudson of Rock Engineering

Consultants, Mr. Kai Front of VTT Technical Research Centre of Finland, and Mrs.

Ursula Sievanen of Saanio Riekkola Consulting Engineers.

Mr. Raimo Ruotsalainen and Mr. Esa Raivonen of

Geological Survey, and Mr. Aimo

Hiironen

of

Posiva deserve special thanks for arranging the review

of

the core samples.


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3

INTRODUCTION

Orientations and properties of fractures were mapped from borehole imaging data of

Olkiluoto boreholes KR9, KR12, KR13 and KR14 and partly boreholes KR1, KR2 and

KR4. The data contained 1996 BIP imaging results from those KR1, KR2 and KR4

sparsely fractured sections, that have not been included into previous interpretation

745 m, Stn1hle 1996) and OPTV imaging results from KR9, KR12, KR13 and KR14

in 2001 2306 m, Wild et al. 2002).

t was necessary to carry out the image mapping as a separate task, because the drilling

and core mapping has been performed well before some months to 2 years) this

work. On general view, as core mapping is traditionally performed immediately on

site, and for the imaging can be performed due to optical conditions not earlier than

h lf a month after drilling, the most efficient mapping procedure has been recognized a

separate work, divided into subtasks that are checked numerically between the steps.

This also saves time and preserves consistency on mapping of the image properties.

Any direct comparison to the actual core mapping data is a separate task and has been

left to the interpretation phase during later works. Background data is referred to

adequate level.

The fracture mapping used extensively the WellCAD software from Advanced Logic

Technology ALT 2001). WellCAD can handle and represent different kind of

borehole data and store the data linked to the presentations. All logs

on

a single file are

displayed on the same scale. The original image data together with borehole deviation

data were imported to WellCAD

by

Ms. Eveliina Tammisto and Mr. Tomas Lehtimaki

Chapter 2). Before mapping, the core samples and images were visually examined to

understand the appearance of

the features on the images. The fractures were mapped

and data transferred to determination

of

properties

by

Ms. Tammisto KR2, KR4, KR9,

KR13), Mr. Eero Heikkinen KR14) and Mr. Lehtimaki KR1, KR12) Chapter 3).

Determination

of

fracture properties from image was completely done by Ms.

Tammisto, a geologist. This was required by the Client, with an intention to maintain

consistency in the properties see Chapter 4). Principles on determination were agreed

with Mr. Jorma Palmen, a geologist. The data was first checked by Mrs. Pirjo Hella

mathematician) to select the observations to be confirmed or rejected. The selected

observations were checked over with the core samples see Chapter 5) at Loppi core

archive KR1, KR2, KR4, KR9, KR12) and in Olkiluoto KR13 and KR14). Ms.

Tammisto, Mr. Lehtimaki and Mr. Heikkinen participated into this work. The sole

purpose

of

checking was to remove most

of

the features encountered

on

imagery that

are not real fractures in sense of core mapping.

Planning

of

the layout for printouts Chapter 6), and data delivery were done partly by

Mr. Heikkinen, partly by Mrs. Hella and Ms Tammisto. Summary tables of different

fracture properties were compiled by Mrs. Hella. Practical arrangements for printing

and data compilation were done

by

Ms. Tammisto.

The preceding data is listed in the Table 1 below. The fracture locations and

intersection angles from core mapping were used in confirming the image observation

before review with the core sample.

Other background data has not been used directly,

but understanding of these has been required to perform the mapping.


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4

The mapping of core sample has listed all penetrative mechanical discontinuities with

their form and roughness on the sample, the mineralogical mapping specifically also

the coating minerals. Hydraulic conductivity is mapped with the flow logging. For

KRl

KR2 and KR4 there has been also dipmeter mapping available, that has brought

out valuable although incomplete orientation data.

Table 1 The preceding material from mapped boreholes

Method

Systematic

core

mapptng

Systematic

mineralogy

mapptng

Hydraulic

flow logging

data

Geophysical

logging

Electrical

dipmeter

BIP imaging

and mapping

Fracture

database

FDB)

OPTV

image

Properties

Length location primary

reference), type open,

filled, tight, slickensided),

intersection angle, partial

orientation, form,

roughness, tentative

mineralogy, frequency,

RQD. All observed ones.

Length, type open,

breakout, slickensided,

filled); thorough fracture

mineralogy and

appearance, thickness of

filling. Not all fractures.

Location and hydraulic

conductivity

of

the

conductive fractures

Reference to lithology,

fracture zones, hydrology

Fractures, general

orientation of banding;

interpretation

of

orientation clusters

Image from whole

borehole, mapped data

from selected sections

those not included to this

work); fracture location,

type, orientation,

aperture, form, tentative

mineralogy, alteration

Merging

of

above

mentioned fracture

properties to same

observations

Non-mapped image data,

mapped in this work

Borehole

KR1

KR2

KR4

KR9

KR12

KR13

KR14

KR1

KR2 KR4

KR9

KR12

KR13,

KR14

KR12

KR1, 2, 4,

9

KR13, 14

all

Reference

Suomen Malmi Oy 1989a

SMOY 1989b, Rautio 1995a

SMOY

1990, Rautio 1995b

Rautio 1996

Niinimaki 2000

Niiinimaki 2001a

Niinimaki 2001 b

Blomqvist et al1992 Gehor et al. 2001a

Gehor et al. 1996

Gehor et al. 1997

Gehor et al. 200 1b

Not available during mapping

Pollanen Rouhiainen 2000.

Rouhiainen 1999.

Not

available during mapping

Niva 1989,

SMOY

1989c, d, 1990b,

Julkunen et al. 1995, 1996, 2000, Lahti

et al. 2001

KR1, 2, 4 Lowit et al 1996

KR9, 12, Not available

13, 14

KR1, 2, 4 Strahle 1996; mapping supplemented by

Karanko

et

al. 2000. Systematic mapping

similar to this work performed for

70o/o

of imagery.

KR 1 2, 4 Saksa et al. 1997, Karanko et al. 2000

KR9, 12, Wild et al. 2002

13, 14


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5

Most important data not received from other than the image mapping are the thorough

orientation, and the aperture o the fractures, combined with the observation type seen

in image. The type o observation is different from each mapping method, and will

rather be supplementing each other than being exclusive.

It was expected that there is a proportion o fractures not seen in the imagery (Saksa et

al. 1997, Karanko et al. 2000).

n

this sense both the other mapping data and the image

mapping results are in their part inadequate to describe the fracture properties alone.

Without a direct comparison to the core data (performed in fracture database

approach), it cannot be said which (kind of) core fractures are not included into the

current observations. A priori assumption is that these may be thin, dark fractures on a

dark background, and probably often perpendicular to the borehole (horizontal lines on

image). Despite o this potential statistical bias, the coverage o core fractures is

expected to be reasonable.

The work in hand concentrated on mapping o the imagery to produce material for later

geological usage. Results were referred with the core sample for quality s sake. These

results should not be considered as the primary data source o fracturing. A relevant

data source these become only after the fracture database has linked core fractures to

the image data. For orientation distributions, the image mapping data is the only

available thorough data set until the database comes available.


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7

IMAGE MATERIAL

Borehole wall images

of

KR1, KR2 and KR4 BIP investigations (Stn1hle 1996) and

OPTV investigations in 2001 from KR9, KR12, KR13 and KR14 (Wild et al. 2002)

were analysed

in

this work. Previous interpretation

of

BIP data (Strahle 1996) was

supplemented from least fractured sections, omitted from the preceding work. The

interpretation included for each borehole the sections shown in Table 2.

Table

2

The extent

o

he interpretation work or this report

Borehole Borehole length range, m

Length,

m Image

type Reference

KR1

341 -500 (sections d e in

267.5 BIP

Strahle 1996

field data),

644-

740 (field data section g)

KR2 300-

390 (sections c d),

2 1

BIP

Strahle 1996

440-

539 (section e)

KR4

390-

480 (sections d and e),

276

BIP Strahle 1996

570 - 739 (sections f g and j)

KR9 40-602

559

OPTV Wild et al. 2002

KR12

40-

793 751 OPTV

Wild et al. 2002

KR13

6-499

494 OPTV

Wild et al. 2002

KR14 9-513.5 502

OPTV

Wild et al. 2002

Total 3050.5

This chapter lists the techniques used, the properties of the images, and the observed

factors in image quality, which have influenced to the mapping and

may

affect to the

results.

2 1

Image logging arrangements

The images consist of bitmaps arranged by depth and orientation. Images have been

acquired by slowly lowering or raising a wire-line camera probe in a borehole and

digitally sampling the borehole image at a dense, constant depth rate.

n

the probe the

light of a LED-string is reflected from borehole wall to a mirror and further projected

onto CCD-element (a video camera). The acquisition geometry, and the parameters of

the image data content are shown in Figure

1.

Each 360 or 720 pixels' row in the image presents a full circle around the borehole

wall captured from a circle on the image. This produces a radial resolution

of

1 or 0.5

degrees, respectively. The specifications of the tools used are presented in Table 3.

The capturing has been performed at a rate of

113

or

115

frames

per

second. The

resulting recording rate or the depth resolution of the image lines is 0.5 or 1.0 mm,

depending on available resolution and logging speed. Recorded image lines were

stored into a computer and transferred to a MO or compact disc. Images contain RGB

data at a colour resolution of 0 ...255 units for each Red, Green and Blue channels

( millions

of

colours ).

Due

to their very large size bitmap images were stored

in 3

150 m slightly overlapping sections during the field work. These data sections

( logging runs ) are indicated

by

letter indexes

a

through

k

in

each borehole.


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8

able 3 The tool and operation specification details for BIP and PTV images

Tool Details BIP OPTV

Probe manufacturer

RaaX Ltd Japan).

Robertson Geologging UK)/

OyO Japan)

Operator

SKB/Geosigma Strahle

Robertson Geologging

Ltd.

1996), Sweden

Wild et al.

2002), UK.

Vertical sampling used 1 mm max 0,25 mm)

0,5 mm

Horizontal sampling used

1° 360 pixels) or 0.49 0.5° 720 pixels) or 0.24 mm

mm at

a 56 mm at 56 mm and 0.33 mm at

76

diameter borehole

mm borehole diameter

Storage size

1Mb/metre

4Mb metre

Data format BIP binary

Initially LGX binary),

received as

Dill

Nominal logging rate

1 5 m/minute

0,5 m/minute

Illumination

LED at mirror LED at camera objective

Recording geometry

Conical mirror Hyperbolical mirror

Cable

Optical Coaxial steel armored

Logging direction

Upwards

Mainly upwards

An image has been oriented to the down side

of

inclined borehole BIP image, Strahle

1996), or

by

a magnetic 3-axial compass Flux gate) to the magnetic North, then

adjusted to the site North OPTV image). Because

of

the rapid changes in local

magnetic field orientation in presence of magnetized minerals in the host rock, the

initial OPTV image has been straightened up by the operator Wild et al. 2002) by

replacing the orientation with Maxibor or Fotobor orientation data Rautio 1996,

Niinimaki 2000, Niinimaki 2001 a b).

Examples

of

the images are in Figures 2 and 3, and their colour histograms in Figures 4

and 5 in Section 2.2 below.


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a) The down-hole tool assembly

NON M GNE11C _

CEN f iV\ ISERS

T R N

SP

A

RE

NT

WINDOW

SONDEHE O

)

XI

X

ACCELEf\O t.IETEf\

c) Screen (camera) view

9

-

Camera field

of

view

Image of

circular mirror

Sample circle

Hypothetical X Y

~ ~ ; ; . . . _ _ _ . pixel grid

b) The

OPTV

functional arrangement

CD

'0

s

r

Video Camera

c) Image

arrangement

Azimuth

N

E

s

Lighting Ring

w

Figure 1 The nomenclature used in the image presentations and alignment. a) the

PTV image tool and b) the camera functional arrangement with c) the

screen view during logging. The 3-component inclinometer and

magnetometer provide the tool orientation reference to magnetic and site

North and

to

borehole deviation. This is used to align the Sample circle in

c) to arrange the image at subsequent depth lines to show the pixels

clockwise, each row starting at reference direction for OPTV the True

North; for BIP the down side) modified from Wild et al 2002). The

sinusoid line on wrapped-out image shows a planar fracture projection.

N


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10

2.2 he image properties

The image properties are differing slightly with respect to the technique used in

logging. Figures 2 - 5 illustrate these differences. Generally, the difference in pixel

resolution can be seen in approximately 1

2

vertical and

1:

1 horizontal scale images in

Figures 2 and

3

This scale is typical for the on-screen mapping and image quality

assessment, but usually not for presentations or printing. The features discussed on this

Section are most clearly visible on computer screen and suffer on quality when printed.

The hair cracks on pegmatite granite, having dark coating, appear slightly jagged in 1

degree

y

1 mm BIP image Figure 2), and the overall resolution gives a bit blurred

impression on this scale. The individual image pixels can be clearly seen in this scale.

The two-fold sharper resolution of OPTV image 0.5 degrees

y

0.5 mm) on less

fractured tonalite gneiss gives a more sharp impression, the individual pixels can not

be clearly distinguished on the image on this scale, and the minor cracks and grain

boundaries do not appear as jagged

as

in BIP. Even the foliation can be seen. Due

to

better resolution the OPTV data storage size is four times larger than for the BIP.

The above-mentioned properties are a result of selecting the data acquisition

parameters and the logging speed rate rather than due to tool functional properties. The

dark coating visible on Figure 2, and the opaque band on Figure 3 are due to borehole

conditions see Section 2.3 in more detail), and not related to the tool performance.

Further to the tool and logging resolution, the tool arrangement has influenced to the

image appearance. This can be seen in Figures 2 and 3 in the differences of lightness

and color saturation. The differences are shown in Figures 4 and 5, in sense of image

analysis, in the RGB channel plots of Figures 2 and 3, respectively. For a shadow cast

on the fracture trace due to the tool arrangement see below), the difference between

BIP and OPTV can be best viewed on images shown in Chapter 4 Figures 15 and 22).

In the BIP tool the light source is located adjacent to the conical mirror, to where the

light reflects perpendicularly from the borehole wall, and further to the camera

objective. The light source is powerful and the distance short, so in places there has

occurred saturation of the colour channels Figure 4). Usually there is also due to large

variation

of

dark and light rock types, an effect

of

automated exposure or shutter speed

light intensity) adjustment. No later adjustments to the images have been applied.

In the OPTV tool the light source is located behind the camera objective, and the

oblique light beam reflects first from the borehole wall to a hyperbolical mirror image

is similar to that from a fish-eye lens), and then to the objective. Despite

of

the strong

light source, the image is rather dark Figure 5). Light intensity is higher with larger

76

mm diameter. t was required to adjustment RGB scale contrast, brightness and colour

intensity). The adjustments were performed for optimal printing on photographic paper

for reporting Wild et al. 2002), and have caused the image colours to convert a bit

false, with slightly too high relative intensity in blue and red components. The light

intensity range is a bit narrow due

to

the initial darkness

of

the image, but the contrast

is adequately sharp for on-screen mapping. No later image enhancement has been

applied for presentations.

The oblique angle of illumination allowed many fractures to cast a shadow on the

image, so these can be observed pretty clearly the difference is seen best on Figures

6a,

15

and 22).


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igure

2

Example ofBIP image data from depth level

340.40

360.66 m of KR2,

granite pegmatite with hair cracks. Scale is approximately 1:2 vertically

and 1:1 horizontally. The pixels on the image can be seen quite well on this

scale. The light grains are slightly overexposed see also Figure 4

for

reference). Thin lines appear jagged.


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2

igure 3

Example of PTV image data from depth level 40.50

40

76 m ofKR9,

tonalite gneiss. Scale is approximately 1:2 vertically and 1:1 horizontally.

The pixels on image are not distinct in this scale. Image is sharp and the

grain boundaries and hair cracks appear rather smooth. Foliation and even

the vertical tool marks can be distinguished. On the other hand, the colour

range is narrow, and the dark grains are a bit underexposed see also

Figure 5 below).


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3

hannel Red

Figure

4

RGB colour channels o the BIP image

in

Figure 2 The colour range

is

well covered although the red channel is partly saturated resulting

to

slightly reddish image and partial overexposure.

Figure 5 RGB colour channels

o

he OPTV image

in

Figure

3

The colour range

is

narrow and show a slight underexposure on all components specifically on

red. This has lead to a slightly bluish image quality. Differences arise from

the tool geometrical arrangements.


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14

2.3 he image quality due to borehole conditions

Generally the quality

of

images is good and accurate. There are several technical

factors influencing the images that also affect the mapping see Table 4).

Table 4 The factors on image quality

Factors on image quality

Reason

Figure

Vertical banding,

Tool decentralization Figure 6a

opaque bands

Flow of

mud in water Figure 6b

Tool marks

Spiral banding, reamer Figure 7a

Vertical scratch lines Figure 7b

Optical conditions

Cloudy water Figure 8a

Coated borehole wall Figure 8b

Stick-slip motion ofprobe

Uneven movement, due to Figures 9a, b

coarse

surface,

cable

tension, flow, low weight

of

tool, or other

Typically the quality deeper in some boreholes has suffered from cloudy water, dark

opaque bands on image or stick-slip motion. Vertical illumination differences see

Figure 6a) occur due to the decentralization of the tool especially for OPTV images

from larger 76 mm diameter boreholes KR13 and KR14). Other vertical banding

occurs on the bottom side of the borehole due to an opaque material flowing in the

borehole water Figure 6b

.

This line helps to confirm the image orientation.

Drilling with an oversize reamer has left spiral marks occurring as 3-5 cm wide

patches, repeated at 13-15 cm period, of different colour than surrounding image see

Figure 7a). On the other hand, tool marks can be seen also as light and narrow vertical

lines Figure

7b

. These occur both in the BIP and the OPTV images.

Dirty borehole water can be seen in many locations, especially at fracture zones. The

feature is more severe when the borehole is freshly drilled, or when other measurement

have been performed shortly before image logging Figure 8a). Boreholes drilled long

before image logging have prominent sedimentation

of

rust or other dark material onto

the wall Figure 8b).

The stick-slip motion of the imaging probe can be seen as horizontal lines of short

vertical banding. The probe had jammed instantaneously but depth record changed

continuously, and the probe has then suddenly jumped over some 5 mm OPTV,

Figure 9b) to

10

cm BIP, Figure 9a), where true image pixels are missing because

they have been replaced with a single value in each column.

The length of each slip movement is smaller in OPTV image than in BIP. This may get

an explanation from the slower 0.5 m/min probe run rate of OPTV compared to 1.5

m/min of BIP. The phenomenon is expected to be caused y friction on the probe due

to coarse wall fractures etc.), or possibly a strong flow along the borehole; or cable

tension, or the light weight

of

the probe itself causing uneven movement, among the

other possible reasons. No direct explanation for this has been available so far.


18/107

5

igure 6a Vertical banding. Probe decentralization KR13, depth

36.70

36.97 m .

Light intensity is higher on the high side of borehole larger distance from probe

produces better illumination due to distance and less narrow reflection angle).


19/107

6

igure 6b Vertical banding Dark material flow along the borehole KR9, depth

231.60 231.95 m). The phenomenon is worst below fracture zones


20/107


21/107

8

igure

7b. Tool marks on the image. Narrow vertical tool scratch lines KR13,

401.10

401.35

m). The water is also rather cloudy dirty)

in

this image, and there is an

opaque band on down side

o

the borehole

to

the east on borehole inclined to the

west).


22/107

19

igure 8a Water quality. Dirty water

in

the borehole KR14, 512.50 512.80

m .

Flowing clay particles can be seen

on

the cent er line

o

the image down side o the

borehole inclined to the north).


23/107

20

igure 8b Water quality. Coated surface o borehole wall KRJ, 342.80 343.05 m .

The coating will accumulate during long period, and is best preserved on the spiral

tool mark.


24/107

2

igure

9a Stick-slip motion. BIP image depth

643.90- 644.15,

KRJ). The length

of

each slippage is

20 30

mm, sometimes even larger, and damages the image severely

when observed. Occurrence is rather rare on sparsely fractured bedrock.


25/107

22

Figure 9b. Stick-slip motion. PTV image KR14, 505.55 - 505.80 m). The length of

each slippage is only 3-5 mm, so the mapping is not totally blocked. The phenomenon

can be thorough over long sections.

In general the BIP image had suffered less from the dirty water and does not indicate

severe stick-slip motion on sections treated in this work. In 1996 the water in the

boreholes had settled down reasonably long. Also the colour intensity is good. On the

other hand the image pixel resolution is clearly poorer than in OPTV.

or

OPTV image

the pixel resolution is good but the image is dark and a minor stick-slip motion makes

the quality at the deeper parts slightly poor. The short time after drilling and other

borehole operations and probably the upward sequence of OPTV logging made other

boreholes than long time settled KR9 to suffer from dirty water conditions. KR12 was

reasonably good but for freshly drilled KR13 and KR14 the condition was less good.


26/107

3

Also the decentralization causes more uneven light distribution in 76 mm diameter

boreholes compared to 56 mm, although the image quality is otherwise better with

larger diameter.

2 4 The preconditioning of the image material

Before the mapping the images were necessary to transport into the software system

used in the mapping.

Original OPTV and BIP data was imported in 10 m sections into WellCAD (version

3.0) working logs and stored into files containing the depth and original measurement

section information (index a - k ) in the file names. During the logging there was at

each run section a 1 - 2 m overlap reproduced in the images. Data import preserved the

original data resolution and image orientation, and allowed scalability on the depth and

the radial axis.

The BIP data was contained in binary files

of

100 m in each, including recorded depth

and orientation. The depth reading was adjusted according to values obtained from the

original report (Stn\hle 1996), representative at the top of each 10 m section. The

adjustments are linear between the top and the bottom of the each 100 m run section.

Residual differences of 10 - 20 cm to core sample can occur due to local deviation

from the trend. The stretch

of

the image over 1 m section is typically 5 - 15 cm. In

places the residual difference may reach 30 cm due to deviation in core mapping depth

(reconstruction of sample has failed),

or

a slight jamming of the probe.

The OPTV image was read in as 10 m sections of Device Independent Bitmap (DIB)

files. Original OPTV records were adjusted

by

setting top

of

subsequent log to the

bottom of previous log. The DIB files do not contain depth or orientation data, but left

edge of image is at the true North, and the top and the bottom depth values for each 1

m section were taken from the field work report (Wild et al. 2002) during the import.

The difference to the core sample is typically less than 10 cm, and at largest less than

30cm

The depth differences were found during the fracture mapping, but were not

systematically corrected for in the images. A proper adjustment would require trend

analysis for each section and non-linear

or

piecewise linear adjustments on that basis.

This was not task of the work.

The imported images were checked for possible errors and proper orientation.

Supplementary data including rock types, crushed borehole intervals, drilling fractures

with orientation and intersection angle, drilling fracture frequency, and the borehole

orientation (azimuth from the North and inclination from the vertical) were presented

in the Well CAD working logs to aid the mapping.


27/107

25

MAPPING THE FRACTURES

In the planning phase o the work, typical appearance

o

the fractures in the images

were compared with those from core sample mapping at Loppi core archive (KR2 and

KR4, KR12)

o

Geological Survey and in Olkiluoto (KR14). The task was to

distinguish the real fractures (penetrative mechanical discontinuities) from narrow

mica bands, veins, foliation etc. possibly appearing similar way on the images.

3 1 Preparation of the material

In Well CAD the images were set to a depth scale o

1:1

- 1:2 and stretched on the log

so that the horizontal scale was approximately the same as the vertical (image 17 - 22

cm wide on screen; aspect ratio close to

1:

1

.

With this setting the pixels on screen

(0.25 mm) were close to the true image resolution.

A new Structure Log to be used in mapping was created on the WellCAD file. The

structure log and the BIP or OPTV image log were set on top

o

each other in exactly

same horizontal and vertical scales. The borehole diameter was set to a correct value

(56 or 76 mm) in the structure log. The tadpole presentations (arrow position on depth

shows the location, on horizontal scale the dip, and the tail points to dip direction,

north to up, east to left etc.)

o

drilling observed fractures (both the 3-D orientation and

the intersection angle) were set on the side

o

these two logs.

3.2

Picking of the features

On the structure logs were drawn numerically the sinusoidal projection traces o the

mapped fracture planes. The software stored the orientation data

o

the planes into data

table. Any (near to) planar feature appears on wrapped-out image as a sinusoid trace,

where the lowest point indicates the dip direction and amplitude (difference from

highest to lowest point) indicates the dip when correlated to the borehole diameter.

When the interpreted traces were combined to the borehole deviation data, the true

orientations o the fractures were obtained and converted to the tables. The data was

presented in a tadpole log beside the image log and compared to the core logging data.

A discontinuity feature in the image was considered to be a potential fracture, when it

differed clearly from the background image; was continuous over the image width, and

was not easily confused to a vein, band o mica plates, foliation or schistosity, or other

thin, similarly orientated features. These criteria are in accordance with those applied

in core mapping. In core mapping the features that penetrate thoroughly over the

sample are reported as fractures. This cannot always be seen reliably for weak class

o

features in the image. Features

o

incomplete continuity (partial fractures - terminating

to another, faulting one; discordant cracks between two adjacent fractures) were agreed

to be left out from the image mapping in this work, although these may be o

importance. Mapping can be continued for these features later according

to

the

requirements.

Typical indications o a fracture are often light in colour over a dark rock type, or dark

in colour over a light rock. These can be few pixels to several millimetres wide, or

even o a sub-pixel width (less than

0.3

-

0.5

mm) when showing clear continuity. A

(drilling induced) breakout or washout o filling material or the borehole wall will

make the observation easier. A black line in an image would indicate open space

(water filled) between the fracture surfaces, a coloured line on the other hand some


28/107

26

kind

of

filling. Examples

of

clearly visible (probable) and poorly visible (potential)

fractures are shown in Figure

10.

Fracture observations were picked from activated structure logs y clicking with

mouse pointer in minimum three points (usually more) on the sinusoidal trace. The

software then calculated the fracture plane matching to the points and displayed the

corresponding projection trace on the log. The orientation data was stored into a file for

editing and exporting. The assigned depth is the midpoint of the trace depth (average

of

high and low points). The trace can be activated and graphically edited to represent the

observations in an optimal way.

3.3

uality criteria of the picking

Depending on the curvature and roughness of the real fracture surface pretty large

deviations from the orientation can occur. The software has directly calculated the

orientation

of

the plane relative

to

the borehole coordinates. The values only need to be

corrected for borehole deviation.

Typical accuracy of the plane fit is some

1 5

degrees. The relative dip is most accurate

when the plane intersects the borehole image nearly perpendicularly. The relative dip

direction is most accurate when the trace is aligned with borehole axis. For a stepped

or undulating trace, a visually well-representative trace was fitted, and there can be

quite a large deviation locally from the plane. This also means that the orientation is

more inaccurate, error can be even several tens of degrees. The final accuracy will

depend on the orientation of the fracture. The true dip direction is very insensitive for

near-horizontal fractures, even differences of some 30 degrees need to be allowed; on

the other hand for near vertical ones the dip will greatly depend on the accuracy of the

plane fit - small curvature

of

the trace or change in the intersection angle with borehole

axis will cause comparably large difference on the true dip.

It

has to be borne in mind

that also the core mapping orientation may in cases be inadequately defined.

The core mapping data from the drilling reports were used to guide the image mapping.

The mapping was done from top to bottom in order to detect depth differences. At this

point it was not possible to combine the mapped fractures together with the fracture

data from the drilling. The features that were clear and continuous on the image were

mapped most easily. The core data were mostly used for checking the correct depth

and orientation of the image, and when poorly visible features were mapped. Extremity

points of traces were avoided to be used in plane fitting.

For each observation a level

of

certainty was determined on basis

of

visibility on image

and on correspondence to the core data depth and orientation. Clearly visible trace was

nominated as probable and poorly visible as possible . Good correspondence with

location (10 cm) and reasonable correspondence with orientation (intersection angle, or

when available the dip direction and dip within 30 degrees) was indicated with label

existing , poor correspondence to either location or orientation with new .

Finally, after each depth section of a borehole was mapped, the structure logs of

observations were copied, and the copy was transformed to the true site coordinate

system. The data was converted to tadpole presentation and compared with oriented

drilling fractures. The data were exported to an Excel sheet. All data sets of a borehole

were merged together. Duplicate observations at overlapping logging run sections (1-2

m) were discarded.


29/107

27

Example o clearly and weakly visible fractures, and the mapped traces, are shown in

pair o images in Figures 1

Oa b.

The probable fracture (green line) is seen as 5 mm

wide continuous trace, with a slight irregularity and curvature on the shape. The

possible fracture (thin black line) is seen as jagged, less planar thin bluish-white line

on both sides

o

the projection line (see red arrows on Figure lOb). Similar but more

planar feature is on the bottom o Figure

10.

This kind o features needed to be

confirmed from the core.

Figure lOa. Examples o racture picking KR9, 141.50-141.75 m). A clear feature

upper, a probable fracture), and a less well visible feature lower, a possible fracture)

with the fitted sinusoid curves

o a plane projection. The poorly visible trace is

indicated on Figure

JOb

arrows).


30/107

28

epth

PTV

~ ~

1:2

E s

w

Figure JOb Examples o racture picking KR9, 141.50-141.75 m). A clear fracture

upper), and a less well visible fracture lower) without sinusoid curves. The red

arrows indicate the points where the undulating and thin, bluish white fracture trace

can be seen on the image. Penetrative continuity can be seen best on screen.

The mapping was done as a separate phase of work and entirely before proceeding to

classification and property determination. To speed up the procedure, mapping was

performed by three different persons a whole borehole for each):

Ms Tammisto, a geologist: KR2, KR4, KR9, KR13, KR14

Mr. Lehtimaki, a geophysicist:

KRI

KR12

Mr. Heikkinen, a geophysicist: KR14


31/107

- -

~

- - - - - - - -

-

- - - - -

- - ---

9

Due to different handwriting , experience and background of persons involved, the

mapping was assumed to lead to slightly a different result with respect to relative

amount and certainty

of

observations (specifically the less visible ones). Some persons

tend to pick more clear features (losing some true data), and some try to find as many

features as possible (with a risk

of

mapping also non-true fractures). The differences

could have been best confirmed with a blind comparison test of a same section to avoid

influence of image quality and rock type.

The procedure of separate mapping of properties, and checking of observations against

the core sample were considered essential. Differences were considered to be equalized

by limiting the determination of properties to a single person, a geologist (Ms.

Tammisto).

Also, most important, using the separate phases made each phase more efficient and

time intensive compared to a situation where all steps were carried out simultaneously.

And, the statistical checking

of

picked properties was more consistent when handling a

single phase simultaneously over a borehole before proceeding to the next phase.


32/107

3

DETERMINATION OF THE PROPERTIES

The determination of fracture properties was performed

by

Ms. Tammisto, a geologist,

alone to maintain consistency of the results. The work was performed with keeping

on

display simultaneously an Excel spreadsheet file with depth and orientation data, and

the WellCAD image log from corresponding depth.

The observation was viewed from the image log and the type, aperture and filling,

level of certainty, form and colour were determined. The possible values for properties

were agreed beforehand. The data was further classified and rearranged during the

checking and analysis procedure (Chapters 5 and 6).

4 1 Design of property parametres

The parameters were designed before the mapping to preserve similarity with the

previous image mapping results (Stn\hle 1996) and core mapping results (Suomen

Malmi Oy 1989a, b, 1990, Rautio 1995a, b, 1996, Niinimaki 2000, 2001 a, b) from the

area, and

on

the other hand the work done on merging the fracture data from different

mappings (Karanko et al. 2000). The technique was adjusted further to this work to

allow thorough mapping of the information visible in the image. The mapping

concentrated to the properties that cannot be reliably or completely obtained from the

core mapping (aperture and orientation were the most important).

On

the other hand,

the other, supporting parameters that are mapped also from the core, were expected to

assist later comparison and merging of the different observations and techniques. The

observation and their illustrations

on

pairs

of

Figures 11-24 are listed

in

Table 5 below.

Table

5

The parameters used in the determination

o

properties

Nos. Properties Comments

Figures

where

illustrated

1 Level

of

Clear visibility on

image=

probable , corresponding the

certainty

core data = existing

Clear visibility on

image=

probable , not corresponding

2

the core data = new

Poor visibility on image = possible , corresponding the 3

core data = existing

Poor visibility on

image=

possible , corresponding the 14

core data = new

2-5 Type Visual properties

of

feature on image; open fractures

15a-d

Partly open fractures

16a-d

Fractures with filling (no visible aperture) 17a-b

Fractures without visual filling or aperture

18a-b

6-7 Aperture, Measurement principle

of

the properties (perpendicular to

19a-b

thickness

the fracture plane)

8-9

Form

Fracture form, seen in image width scale (planarity, steps, 20a f

undulation) and in local mm scale (local smoothness)

21a-d

11- Col

or

Color or grayscale data visible in different conditions,

22a-b

3

ranging from darkness or gray value to col or dye 23a-b

14 Seepage Indication

of

material inflow from the surface 24


33/107

32

The determined properties and their possible values are summarized in Table 6

Distributions o the fractures according to their class before checking are listed in

Table 7 The details on mapping parameters are presented below.

Level

o

certainty 1)

was used as a guiding basis for internal quality analysis o the

mapping. Also the observations to be checked were selected on this basis (Chapter 5).

Checking maintains the probable/possible classifications on Table 7 based on the

image visibility, but will alter the existing/new to checked/rejected when

applicable, to Table

9

The rejected class is not maintained in the final results (Table

9). The possible ones were checked systematically, the probable ones only with

few checks. A probable feature is so clear that there is no doubt on its determination

as a fracture. Observation was possible when it was not sure from image whether

there was a fracture or a vein or whether the observation was penetrative or not.

Feature was considered existing (fracture) when there were adequately similarly

oriented observations at the same depth level in the drilling report, and new when

there were no correspondence on either location or orientation. Also depth differences

between the image and core sample result in possible class observations. The typical

observations on different categories are illustrated in Figures 11 - 14.

Fracture type

2

- 5)

consists o four independent observations. These were

openness , filling , alteration and tightness . The previously used mutually

excluding types open-with filling-closed were considered to be inadequate so these

parameters were mapped separately. This results to fractures that can be with filling

and/or open. Anyhow, a closed fracture was not classified as an open fracture or a

fracture with filling, because it cannot be judged from visual appearance on image.

The type is a property that is observed from image at the intersection line

o

the plane

(along the plane), as there is no view onto the plane surface in image like there is in the

core. Observations are limited to their scale, i.e. features clearly smaller in thickness as

the pixel size are assigned with property closed , although there can be filling

material

or

aperture thinner than 0,25 mm. Thus a closed fracture in the image can

quite well be a fracture with filling in core mapping, etc. The open and partly open

fractures may be seen

as

black pixels in BIP OPTV, and shadow in OPTV. Filling

can be present also when a fracture is open . Partial filling has not been separated fom

complete in mapping. And, i there is no observation with filling , it does not mean

there would not be filling on the surface. The Figures 15 - 18 below show examples o

different fracture types.

The thickness 6)

o the visible solid filling between the fracture surfaces and the

aperture 7)

(a distance perpendicularly between fracture surfaces being apart each

another) were measured in millimeters from central part o the fracture trace,

perpendicular to the fracture plane, or, when the fracture was partly open, from the

open part. This was thought as the most representative value. At the peak points o the

projection (upper or

lower end) the cut section is wider and usually more interfered by

drilling than at the central part. Thickness does not include aperture, nor vice versa.

Both aperture and thickness can vary considerably along the trace, so these estimates

should not be counted together to a total width estimate.


34/107

33

The aperture may partly or totally originate from drilling induced physical failure

(break-out) or washout of material between the surfaces, or even between closely

spaced several fractures, or from clay-filled or brecciated larger zone. f the

observation is linked to clearly collapsed or washed wide section (a narrow zone), the

edges have been mapped as separate observations. The fractures inside the zones have

been picked and classified only

if

they appear clearly. The image is the only

opportunity to get a direct openness indication

of

a fracture surface, as usually the

reconstruction of the core sample has no means to observe it; and there are rare n

s tu

indications on open fractures in other than hydraulic conductivity data. Figure

19

shows an example ofmeasuring the aperture and thickness.

The form and roughness

8

-

9)

of the surface have been described as a deviation

from the plane (from the sinusoid trace) in two separate scales. In the scale

of

the

wrapped-out image (200 - 250 mm), form 8) was analyzed. When the fracture trace

follows accurately enough the sinusoid

of

a plane, observation is planar .

f

the trace

deviates several millimeters in any point, it is undulating (i.e. curved). In case the

surface changes suddenly several millimeters, it is denoted as stepped . In the smaller

few millimeter scale, roughness 9) was analyzed. The fracture is smooth if there is

no observable deviation from the sinusoid, and otherwise rough . Examples

of

different forms of the fractures in different scales are shown in Figures 20 - 21.

The image observation is obtained from the side of the fracture plane, not from the

surface as in the core mapping, so the observations may not be quite comparable to the

surface roughness. Because the property is clearly observable, and also indicates the

accuracy of the plane fitting, it was recorded.

The colour 11 - 13) of fracture filling was assessed on three-level scale. Depending

on the colour and darkness of the background, and quality of the image, the colour

could be observed as

brightness 11 dark or light; especially when other colours cannot be seen)

grey intensity (12, white-grey-black)

colour dye (13, brown-red-yellow-green-blue).

In certain cases there are two or more separate colours, seen partially or layered on the

trace. From OPTV data the colour was observed from initial field data records, as in

the final data the contrast adjustment has altered the colours. In Figures 22 and 23

examples

of

the colour or grey intensity observation are shown.

Seepage 14) can be observed only when some material flows into the borehole from a

fracture and the colour of flowing material differs from the background. Outflow

cannot be observed. The flow from the fracture or along the borehole can be seen as a

curved fan on the image. The fan initiates from channels on fracture surface. t can be

guided towards the high side (light, warmer water) of the borehole, or to the low side

(heavier, cold water or material) and tur narrower before it vanishes within few tens

of

centimeters. A visual observation at close probe view indicated that such trace is a

turbulent flow of material in the water. t can also be a stain of material sedimented on

the wall over a longer time. Direction (upwards or downwards) has been marked for

specific fractures. The Figure 24 shows an example

of

seepage location.


35/107

34

able 6

The parameters treated during mapping with allowed values.

No.

Property

Values omments

1

Level of

Probable, Drilling fractures at same ±

10

cm depth range, orientation

certainty

existing similar to the image observation within 30 degs, clear on

image

Possible,

Drilling fractures a t same ± 10 cm depth range, orientation

existing different from the image observation, and/or not clear on

image

Probable,

Drilling fractures not observed at same ± 10 cm depth range,

new or orientation clearly different to the image observation;

however clearly visible and fracture-like

Possible,

Drilling fractures are not observed at same depth range ea.

new ±

10

cm, or orientation is different to the

TV

observation,

and are not clearly observable from image

2

Openness Open Projections apart from each other

Partly open Part of surfaces apart from each other, part are closed when

seen in the observation scale

Not open Surfaces are adjacent in the observation scale

3

Filling With filling

Filling seen in image (coloured pixels, different from

background)

No filling

No filling seen in image ( in observation scale)

4

Alteration Altered

Fracture lines are discoloured or disintegrated (rust, etc).

Fresh Fracture lines intact, no colour changes

5

Tightness

Not closed

Surfaces are either apart, separated with some material, or

weathering is observed

Closed

In the observation scale 0,25- 0 5 mm) the surfaces are

closed, there is no filling and fracture is not weathered.

Excludes the others.

Filling thickness

Measured from central part of trace (in mm)

7

Aperture

Central part of trace, for partly open from the open part (in

mm)

8

Shape Planar

On image width scale

undulating

stepped

9

Roughness Smooth

On few mm scale

Rough

10

Mineral Possible

An estimate, not stored n final data

mineral

11

Darkness Dark

Only when image dark and no color or grey scale can be

Light

estimated

12

Grey intensity

Black Other than colour dye

Grey

White

13

Colour dye Yellow

Other than grey intensity

Red

Green

Brown

14

Seepage

Upwards Material flow into borehole and its direction

Downwards

No


36/107

35

PTV

e

1:2

E

N

9

Drill obs tract

7JD

Figure 11 Existing and probable observation KR14, 72 80 73.10 m green sinusoid

and tadpole). Similar core fracture black tadpole) is observed close to the same depth.

The trace is clear and continuous on image.


37/107

36

epth

PlV

e

1:2

r

N

E

N

0

90

Drill s fract

90

Figure 12a. Existing and possible observation KR14, 73.60- 73.80

m,

green sinusoid

and tadpole). A core fracture is observed close to the same depth black tadpole). The

trace on image is a bit vague, and its continuity uncertain a white undulating line).

The dip is steep; the dip direction o a steep fracture can easily turn 180 degrees

in

a

vertical borehole

i

he feature is undulating; real dip difference is approx. 3 0 degrees

over the vertical.


38/107

37

OPl\1

:2

N

N

N s

Jtl

N

Figure 12b Existing and possible observation KR14, 73.60 73.80 m without the

sinusoid curve. The red arrows clearly indicate the undulating white line, a possible

fracture with filling. The real reported fracture can be at slightly different position

i

re-opened.


39/107

38

Pmjection 11 9

igure 13a A new and probable observation KR9, 70.00 70.20 m . Similar core

fractures are not observed near to the same depth, but the observation is clear on

image. The fracture clearly

is

there, and typically when checking from the core sample

the observation was confirmed. It is possible that a welded fracture has not been

reported in drilling report although it could have been observed i broken apart. The

form deviates significantly from planar see arrows

on

Figure 13b).


40/107

39

Depth

OPTV

:2

E

s

w

Projection

E s w

Figure 13b. New and probable observation KR9, 70.00 70.20 m without the

sinusoid curve. The arrows indicate the position where the continuous, undulating line

is best observed on image.


41/107

4

Pmj

ectjon 1 9

Figure 14a New and possible observation KR9, 71.55-71.75 m, black line and

tadpole, on sparsely fractured rock . Similar core fractures are not observed close to

the same depth, and the observation is not very clear on image. It is possible that there

is a mica plate originated continuity on core, or a hair crack i seen on image is not

penetrative; or the fracture has not been observed

on

the core mapping. The checking

o these features on the core either led to rejection

o

observation, but

in

few cases a

new real fracture has been added to the database.


42/107

4

epth

PTV

:2

E

s

w

Projection

E

s

w

71 6

Figure 14b. New nd possible observation KR9, 71.55-71.75 m) without the sinusoid

curve. The arrows indicate where the faint trace

of

possible hair crack has been seen

on image black, continuous undulating line between feldspar grains).


43/107

42

Figure 15a An open fracture with filling

KR9, 13 7

55

13

7

7

5

m.).

The arrow

shows the location where some filling material has been observed. The filling is not

penetrative in this case and may have partly washed out during drilling.


44/107

Depth

:2

137 6

43

E

PTV

s

w

Figure 15b. An open fracture, with fi lling KR9, 137.55 137.75 m). The sinusoid and

arrow removed so the trace is more clearly seen.


45/107

Figure 15c An open fracture with sinusoid curve, no visible filling KR12, 713.35

713.55). There is some indication

o

the drilling debris lain on bottom

o

the surface,

but no compact filling between the surfaces. Either filling did not exist on this location,

or has been completely washed away.


46/107

Depth

:2

713 4

45

OPTV

s

w

N

Figure 15d

n

open fracture without sinusoid curve, no visible fill ing KR12, 713.35

7

.55). The same image as in Figure 15a.


47/107

6

Figure 16a A partly open fracture, with filling KR12, 738.35- 738.50 m . There

is

clearly compact filling calcite?) between the fracture surfaces, and

p rt of

he

fracture trace is clearly open on North left) side.


48/107

7

Depth

PTV

~ ~

:2

s

w

738 4

Figure 16b A partly open fracture, with filling KR12, 738.35- 738.50

m .

The same

image as on Figure 16b.


49/107

8

Figure 16c A partly open fracture with sinusoid curve, no visible filling KR12,

713.15- 713.35 . The aperture is clearly seen but no indication

o

any filling material

is present.


50/107

49

epth

PTV

:2

~ ~

N

s

w

N

713 .2

Figure 16d A partly open fracture without sinusoid curve, no filling KR12, 713.15

713.35). The same image as

in

Figure

16c


51/107

50

Figure 17a

A fracture with filling, neither open nor partly open KR9, 142.65

142.80

m).

The filling, light in colour, can be seen on west right)

p rt

ofthe trace.

In

the observation scale, there cannot be seen any aperture or breakout fracture

is

healed).


52/107

epth

:2

N

5

E

OPTV

w

N

Figure 17b. A fracture with filling, neither open nor partly open KR9,

142 65

142.80

m .

The same image as in Figure17

a.


53/107

52

epth

OPTV

1:2

r

N E S W N

PROJE TION

N

E

s w N

Figure 18a

A closed fracture KR9, 41.70-41.90

m)

with sinusoid curve. There is a

narrow curved crack trace cutting the mineral grains that does not allow any

aperture or filling material to be observed.


54/107

5

epth

OPTV

2

s

w

4 B

Figure 18b A closed fracture KR9,

41

.70-41.90 m) without sinusoid curve. The red

arrows show the trace. There is no aperture or filling visible on the trace length. This

does not exclude the possibility

o

illing observed on the surface, or a minor less than

0.25 mm) aperture being present.


55/107

54

Figure 19a The measurement principle o aperture KRJ2, 94.95 95.20 m .

The

reading

is

taken from the mid part o the trace, between the surfaces apart in the

image.


56/107

Figure 19b The measurement principle of thickness KR12,

74.80

75.00 m . The

reading is taken from the mid par t

of

he trace, over the filling material.


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56

Figure 20a Fracture form in image width scale 200 mm), planar KR9, 147.85

148.05 m with sinusoid curve. The form follows nicely the sinusoid curve over the

image width.


58/107

Depth

:2

148.0

E

57

OPTV

s

w

igure

20b.

Fracture form in image width scale 200 mm), planar

KR9,

147.85

148. 05 m) without sinusoid curve. The same image as in Figure 20a.


59/107

~

8

Figure 20c

Fracture form

in

image width scale 200 mm), undulating KR12, 65.55-

65.80 m with sinusoid curve. The trace form is clearly deviating from the sinusoid

curve o plane projection.


60/107

59

Depth

OPTV

1:2

1 N E S W N

6: 6

Figure 20d Fracture form in image width scale 200 mm), undulating KR12, 65 55

65.80

m

without sinusoid curve. The image is same as

in

Figure 20c.


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6

Figure 20e

Fracture form in image width scale 200 mm), stepped fracture KR12

61.35 61.66 m with sinusoid curve. There is clearly a step probable brittle minor

fault) at the middle

o

the trace. A differently oriented minor crack seems

to

cut the

fracture mapped.


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61

Dep h

OPl\1

1 2

61 6

Figure 20f. Fracture form in image width scale 200 mm), stepped fracture KR12

61.35- 61.66 m without sinusoid curve.


63/107

6

Figure 2

a

Fracture form

in

local, mm scale smooth KR12, 66.00 66.10 m with

sinusoid curve. The surface

is

even, no deviation from planar form is seen.

OPTV

1:2

E s

w

Figure

2lb

Fracture form

in

local, mm scale smooth KR12,

66 00

66.10

m

without

sinusoid curve. The same image as

in

Figure 21

a.


64/107

6

igure 21

c.

Fracture form in local, mm scale rough fracture KR12, 62.15 62.35 m

with sinusoid curve. The local f w mm variation on the surface from the planar

projection is clearly seen.


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64

Depth

PTV

N

E

s

w

N

igure

2 d

Fracture form

in

local, mm scale rough fracture KR12, 62.15 62.35 m)

without sinusoid curve. The same image as in Figure

21 c


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6

Figure 22a A white fracture KRJ , 370.00- 370.20

m

with sinusoid curve. The filling

material seen between the surfaces is white calcite, kaolinite?)

in

eo/or.


67/107

Depth

BIPS

N s

w

Figure 22b A white fracture KRJ, 370.00- 370.20

m

without sinusoid curve. The

same image as in Figure 22a.

N


68/107

7

Figure 23a

A grey fracture

KR2, 313.9 314.15 m)

with sinusoid curve. The dark

grey eo/or

of

illing between the surfaces is clearly seen quartz, chlorite?).


69/107

epth

1:2

314.0

N

E

68

IP

s

w

Figure 3

b A grey fracture

KR2,

313 9 314 15

m)

without sinusoid curve The

same image as in Figure 23a

N


70/107

9

Figure 24a

A location where material flows into the borehole (KR9,

280.54

280.82

m) with sinusoid curve. There is a fan ofmaterial flowing upwards, tending to reach

the high side

of

he borehole (north), and a thicker line reaching to the down side

(south)

of

he borehole, flowing downwards. The first is probably soluble material and

water flowing, the latter probably solid material rending to depth, or heavier water

fraction.


71/107

Depth

m:2m R)

N

200 8

7

E

PTV

s

w

Figure 24b A location where materia/flows into the borehole K.R9, 280.54 280.82

m without sinusoid curve. The same image as

in

Figure 24a.

N


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71

There was no attempt to observe existence

of

an alteration rim around the fracture trace

or to measure its thickness. Neither were assessed the filling properties (grain size,

compactness, clay, carbonate, quartz) as these were considered to be best mapped from

the core. Both can be estimated from the image to some extent, but the latter not with a

certainty.

4 2 The distribution of mapping results according to level of confidence

The original mapping resulted in 7933 fractures for 3050 m, see Table 7 for

observations in each borehole before checking.

Table

7

The distribution and amount o ractures before checking

K.Rl, KR2,

KR4 KR9

KR12,

KR13,N

KR14,

N( ) N( ) N( ) N( )

N( )

(%) N( )

Existing/ 226 (60)

98 (27) 99 (41) 887 (71) 1797 (71) 1073 (67) 615 (40)

probable

Existing/ 86 (23)

90 (25) 81 (33) 134 (11) 321 (13)

205 (13)

110 (7)

possible

New/

14

(4)

101 (28) 38 (16) 104 (8) 201 (8) 155 (10) 171(11)

probable

New/ 52 (14) 77 (21) 26 (11) 124 (10)

227 (9) 161 (10)

660 (42)

possible

Probable 240 (63) 199 (54) 137 (56) 991 (79) 1998 (78) 1228 (77) 786(51)

Possible 138 (37) 167 (46) 107 (44) 258 (21) 548 (22) 366 (23)

770 (49)

Total 378 366 244 1249 2546

1594 1556

Obs. length 267.5 201 276 559 751

494 502

m

Observations 1.41 1.82 0.88 2.23 3.39

3.23 3.10

/m

Fractures/m 1.42

1.68 0.85

2.24 3.62 3.77

1.54

(drilling)

Initial fracture frequencies are similar to those observed in the core mapping. The host

rock sections (outside defined fracture zones) in KRl, KR2 and KR4 indicate less

fractures than the completely mapped other boreholes. Less fractured KR14 is an

exception in terms

of

comparison with the core mapping data.

The proportions

of

probable and possible features distribute interestingly. The BIP

mapped boreholes KRl, KR2 and KR4 show fewer probable observations

(54-

63%)

than the OPTV mapped KR9, KR12, KR13 (77-79%).

An

exception

of

this trend is

KR14 (51%), which is least fractured and was mapped by a different person. Also the

image is poor due to stick-slip interference and dirty water. Class existing/ possible

is more frequent

(23-

33%) in BIP image mapping than in OPTV mapping (7-13%).

For new fractures there is more variation in BIP image results (4-28%) than in

OPTV (8-11 %, except new possible 42% in KR14). These may arise from the

correctness

of

the depth adjustment in BIP images or core sample.


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72

The certainty class was used to decide which borehole sections would be checked over

with the core sample.

t

appeared that the better resolution

o

OPTV image allows to

observe the features with greater certainty, although the relative amount

o

the

observations does not depend so much on the image source.

n

analysis

o

the different

certainty classes it was observed that the possible observations are more often

closed or with filling than the others. So the checking against the core sample was

focused into existing/possible , new/possible and new/probable , leaving the

existing/probable that was already linked to the core sample mapping for lesser

interest as it had external confirmation from the drilling data.


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73

CHECKING THE OBSERVATIONS WITH THE CORE SAMPLES

5 1

The checking procedures

The observations were checked towards the core samples at the core sample archive

of

Geological Survey of Finland in Loppi (boreholes KRl, KR2, KR4, KR9 and KR12),

and at Olkiluoto (KR13 and KR14). All the observations of classes 'New, Possible

and New, Probable were checked systematically as well as most

of

the observations

Existing, Possible .

The images and results were compared with the samples. The results

of

the first

checked borehole (KR2) were analyzed to allow guidance of the remaining work.

Checking required typically a day for 300- 400 observations. The rate depended on

fracture frequency, proportion

of

observations to be checked, rock type, quality

of

image and the accuracy

of

the depth adjustment. The checked fractures received status

probable , and are indicated also with a label confirmed in the final database. The

others have a label unchecked . Rejected not a fracture -observations have been

removed from the final fracture lists. Influence

of

checking is presented in Table 8.

5.2

The results of the checking

After the checking 6138 fractures remained in the data (78% of the initial amount).

Generally some 78-88%

of

observations remained, except for KR4 (62%) and KR14

(5lo/o).

Table

8

Influence

o

checking

Inspection

KRl,

KR2, KR4, KR9, KR12, KR13,

KR14,

N( )

N o/o) N( )

N( )

N( ) N( ) N( )

Initially

378 366

244 1249 2546 1594 1556

Final

295 (78)

321 (88) 148 (61) 1026 (82) 2228 1342 (84)

778 (51)

(88)

Checked 153 (40) 213 (58) 151 (62) 386 (31) 804 (32) 535 (34) 969 (63)

Rejected 83 (22) 58 (16)

96 (39) 223 (18) 317(12)

252 (16) 770 (50)

Rejected

of

54% 27% 64% 58% 39% 47% 79%

checked

Exist/Cert 2 (1%, 1 (0%,

3 (3%, 13 1 %,

15 (1%, 10

1

%, 27 (4%,

rejected N=226) N=98) N=99) N= 887) N=1797) N=1073) N=604)

Exist/ uncert

36 (42%,

14 (16%, 48 (59%, 74 (55%, 99 (31%, 78 (38%, 63 (57%,

rejected N=86) N=90) N=81) N=134) N=321)

N= 205) N=llO)

New/cert 5 (36%,

11 11 %,

21

(55%, 44 (42%, 51 (25%, 59 (38 %, 95 (34%,

rejected N=14) N=lOl) N=38)

N=104) N=201) N=155) N=278)

New/uncert 40 (77%, 32 (42%,

24 (92%, 92 (74%,

152 105 (65%,

585 91 %,

rejected

N=52) N=77)

N=26) N=124) (67%, N=161) N=644)

N=227)

New,

0

13

(4%)

0 0

1 (0%)

0

12 (1.5%)

confirmed

Frequency

1.10

1.60

0.54 1.84 pes/m 2.97 2.72 1.55

pes/m pes/m

pes/m pes/m pes/m pes/m

Drilling

1.42

1.68

0.85 2.24 pes/m 3.62 3.77 pes/m 1.54

frequency pes/m pes/m pes/m pes/m pes/m


75/107

74

Varying by borehole some 40-62% of the observations were checked from BIP, and

from the checked ones 27-64% were rejected, the others confirmed. For KR9-KR13

OPTV 31 - 34% were checked, and 39-58% of the checked ones were rejected, others

were confirmed. In KR14 63%

of

observations was checked and 79% of the checked

ones were rejected, the remaining 21% confirmed. Typically the rejected fractures

represented rather types closed or fractures with filling . Any of the rejected

fractures were

of

types open or partly open .

The fractures classified as Existing, Probable were checked only occasionally (2-3%)

especially when a depth error or disorientation of the core sample were suspected. A

proportion of 0-4%

of

all were rejected (some one-third of the checked ones in this

class). Table 9 shows the proportion of fractures in the certainty classes after checking.

The properties probable and possible practically lost their meaning in checking.

The few possible observations are related to locations where the sample has been

missing. The greatest remaining uncertainty is found for observations initially

belonging to the class possible , as these have not been checked as extensively as the

others. Generally these are linked to similarly oriented core mapping fractures at the

same depth level and usually are very clear in the image. The information has not been

merged in this work. According to tentative observation some 1 o of all the features in

this class would change when checked, mostly at locations with depth or orientation

errors.

n

any case the core mapping and image mapping would produce slightly

different results due to e.g. accuracy reasons.

The proportion 6 - 14% of new fractures suggests, that there are some fractures

unobserved in the core sample mapping. Some

of

these may barely indicate

an

inadequate depth value in core reconstruction (deviation from the image depth

adjustment), or an uncorrected drift on image depth value.

Table 9 Certainty classes after checking Those rejected are not counted or in the

proportions The possible ones confirmed have been transferred to probable class

Borehole/ KRl

KR

KR4

KR9 KR12 KR13

KR14

Certainty (N=295) (N=321) (N=148) (N=1026) (N=2228)

(N=1342)

(N=778)

Existing/ 272 148 134

91

%) 943 (92%) 2029 1197 662 (85%)

Probable

(92 ) (46%) (91 ) (89 )

Existing/ 5 (2%)

30 (9%) 2 (1%) 3 (0%) 3 (0.1%)

7 (1%) 7 (1%)

Possible

New/ 14 (5%)

130

11

(7%) 74 (7%) 190 (8.5%) 133 (10%)

105 (13%)

Probable (40%)

New/ 4 (1%)

13

(4%) 1 (1%)

5 (0%)

6 (0.3%)

3 (0%) 4 (1%)

Possible


76/107

75

RESULTS

6 1

Contents of the results

n

total 613 8 fractures were included into the final results after checking. The

frequencies and amount represent 81%

of

the core sample fractures (63% - 100% for

different boreholes). Lowest proportion is found in KR4 (63%). Reason might emerge

from image quality or fracture type distribution, or accuracy in the image adjustment.

Highest proportions (95% and 100%) are in KR2 (BIP) and KR14 (OPTV). The former

was checked first and in more detail than the others. From the latter smaller scale and

more detailed possible fractures were mapped resulting to a greater amount of rejected

observations at the checking phase. The proportion for other boreholes is 77 - 82%.

There are probably some 0-5% new observations in different boreholes. The new

fractures may be drilling induced, from core loss areas (not from triple-tube drilled

KR13 and KR14), or features that have not been reported from sample because

of

being closed, but can be mapped from image.

The coverage of previous BIP interpretation (Strahle 1996) was checked for

comparison. Mapping has covered in average 43% of the core mapping reported

fractures, varying between 22 - 60% depending on borehole and depth interval.

Proportions of observed fractures were less near to surface where the fracture

frequency is highest. Mapping in 1996 did not utilize the core mapping data but was

based on image data alone, and recorded only the most clear indications.

6.2

Fracture type distributions

The fracture type distribution was analyzed. The open , partly open and with

filling types can exist simultaneously forming five major classes whereas the sixth

major class closed is excluding the others by definition. The class altered is met

only in boreholes KR2 and KR13, probably reflecting local variation in bedrock

conditions. Distribution of types in results are in Table 10 and in Figures 25 - 32.

Table 10 Fracture type distributions

Borehole/

KRl KR2

KR4 KR9

KR 2

KR 3

KR 4 All

Types

N=295 N=321

N=148 N=1026 N=2228 N=1338 N=778 N=6134

Open

0 (0%) 0 (0%) 1 (0.6%) 6 (0.6%)

15

(0.7%) 29 (2.2%) 5 (0.6%) 56

(0.9%)

Partly 0 (0%) 0 (0%) 0 (0%) 16 56 (2.5%) 45 (3.4%)

18

135

open

(1.6%)

(2.3%) (2.2%)

Open,

2 (1%)

1 (0.3%)

2 (1.2%)

1 (0.1 %) 2 (0.1 %) 3 (0.2%) 3 (0.4%)

14

with

(0.2%)

fillin2

Partly 0 (0%) 3 (1%) 10

13

25 (1.1%) 45 3 .3%)

19

115

open, with

(6.8%)

(1.3%) (2.4%) (1.9%)

fillin2

With

181

256

114 646 1400 915

536

4048

fillin2

(61%)

(80%)

(77%) (63%) (62

posiva 2002 22 working report web

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