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{\bf 3. FIELD PROGRAM}
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The Sudbury area field program for the vertical seismic profiling (VSP) and
borehole logging took place between June 13 and June 18, 1994. The VSP work was
conducted by a crew from the University of Alberta and the Geological Survey of Canada
with logistical support from the IETS office in Copper Cliff.
Three boreholes were
logged: 85527 (McCready East), 85597 (Gertrude), and 60100 (Blezard).  Refer to 
Fig. 2.1 for the location of all boreholes logged for IETS in the Sudbury
area.  Hole 85527 was logged on June 14 and 15 from a depth of 1165m to 130m.
Access to this location was very difficult and the GSC vehicle was needed to 
pull the VSP aquisition system into place.  The McCready hole was 
relatively close (.5 km) to active mines and noise from underground
drilling is apparent on the VSP data.  Borehole 85597 was logged on June
16 from a depth of 295m to 50m and hole 60100 was logged on June 17 from a 
depth of 630m to 40m.  Again, access was difficult to borehole 60100 and the
University of Alberta truck needed assistance to reach the site.  Borehole
60100 was also very close to Hwy 11 (60 m) and traffic noise is strong on the
VSP records.
\smallskip
Atomic Energy of Canada (AECL) was contracted to perform the borehole logging
for the INCO IPP and logged the same boreholes as mentioned above.  AECL did 
caliper, sonic and density logging in 85597 and sonic and density logs in 
85527 and 60100.  Please refer to Annex A.2 for a complete report on the AECL
logging program.
\smallskip
The field procedure for VSP acquisition involves positioning the receiver at a
known depth in the borehole, locking the tool in place, and recording an
explosive blast detonated at the surface.  The tool is then moved to another
position and the blast is repeated at the same surface location.  The full
length of the borehole is logged in this manner, at a predetermined receiver
spacing.  The equipment used by the University of Alberta for the VSP work 
was as follows: 
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{\sl Downhole Geophone:} A SIE T42 3 component wall-locking geophone package
was used.
The package contains 14 Hz geophones mounted vertically, perpendicular 
to the wellbore wall and normal to the wellbore wall.
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{\sl Wireline Unit:} The wireline unit consisted of a
1200 m, seven conductor, 1/4" steel armoured
cable.  Power was 
provided by a 1.5 hp SRC controlled electric motor supplied with a 4 KW
Generator.  The System is trailer mounted.
\smallskip\noindent
{\sl Data acquisition:}  
A 12 Channel Bison Model 5000 data acquisition unit
was used, with data storage accomplished on a 
Laptop PC in the field.  The Bison was triggered by the 
blasting box used to detonate the source either by direct wire connection to
the same box used by the shooters, or by a separate box which
was time synchronized to the shooters box.
\smallskip
The source for the VSP work was provided by detonating 8 oz (227 gm) 
8L Super Prime boosters in 2-3 m deep, water filled pits or, in the case of 
borehole 85527 (McCready), in 5m deep shotholes drilled to bedrock.  The 
boosters were detonated with 5m Vibrodet Electric (seismic) blasting caps.  In
the pits the booster was pushed into the soft sand/clay at the base of the pit
and very good source containment was achieved.  In the shotholes source
containment was more problematic.  Attempts to contain the source by covering
the shothole were fruitless as the material was blasted into the air by the
shot, becoming projectiles.  It was decided to just fill the shotholes
with water prior to the shot and it turned out the source was more than strong
enough to provide good downgoing signal even with significant energy going
out the top of the shothole.  Water was provided by pumping from a nearby pond
with a pump borrowed from IETS.  Four shotholes were drilled at the McCready
site in a small grid (3m X 3m) and after 1 hole became unusable because of 
rock breakup at surface, another shothole would be used.  Fig. 3.1 
demonstrates the consistency of the source signal for the McCready hole and
compares it to the source signals generated at hole 60100 (Blezard) where a
pit was used. During data processing, deconvolution and spectral whitening
are used to compensate for minor waveform variations.
 The explosives for this survey were supplied Canex Explosives in
Sudbury.  Blasting boxes were provided by the GSC and all the shooting was
done by GSC personnel.  In addition to the downhole geophones, three surface
geophones were positioned between the recording truck and the pit.  These
surface channels were also recorded for each shot and later used to calibrate
and correct small travel-time errors assoiciated with source variations.
\smallskip
The filters on the acquisition system were set to 500 Hz (high cut) and 20 Hz
(low cut) and data was recorded to .6 seconds at a sample rate of .1 ms.  
The VSP acquisition was relatively trouble-free with only minor problems
related to computer crashes and some misfires due to triggering problems.  
The VSP data was stored on hard disk and also archived to floppy disks in the
field.  The data was sorted and formatted to Landmark/ITA format by the University of
Alberta before being sent to the GSC for processing and interpretation.
\smallskip
In Sudbury, the VSP acquisition and sonic logging were relatively trouble-free,
but is was immediately apparent from the paper records that the data quality
suffered in the vicinity of massive sulphides. We believe that the
highly conductive environment associated with massive sulphides
degrades the performance of conventional borehole seismic tools.
\bye