Aug2007a

Aug2007a
Annals of Glaciology 47 2007
73
Drilling comparison in ‘warm ice’ and drill design comparison
L. AUGUSTIN,1* H. MOTOYAMA,2 F. WILHELMS,3 S. JOHNSEN,4 S.B. HANSEN,4
P. TALALAY,5 N. VASILIEV5
1
Laboratoire de Glaciologie et Géophysique de l’Environnement du CNRS
(associé à l’Université Joseph Fourier – Grenoble I), 54 rue Molière, BP 96, 38402 Saint-Martin-d’Hères Cedex, France
E-mail: [email protected]
2
National Institute of Polar Research, Kaga 1-9-10, Itabashi-Ku, Tokyo 173-8515, Japan
3
Alfred-Wegener-Institut für Polar- und Meersforschung, Am Handelshafen 12, D-27570 Bremerhaven, Germany
4
Department of Geophysics, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen, Denmark
5
St Petersburg State Mining Institute, Line 21, 2, 199106 St Petersburg, Russia
ABSTRACT. For the deep ice-core drilling community, the 2005/06 Antarctic season was an exciting
and fruitful one. In three different Antarctic locations, Dome Fuji, EPICA DML and Vostok, deep
drillings approached bedrock (the ice–water interface in the case of Vostok), emulating what had
previously been achieved at NorthGRIP, Greenland, (summer 2003 and 2004) and at EPICA Dome C2,
Antarctica (season 2004/05). For the first time in ice-core drilling history, three different types of drill
(KEMS, JARE and EPICA) simultaneously reached the depth of ‘warm ice’ under high pressure. After
excellent progress at each site, the drilling rate dropped and the drilling teams had to deal with refrozen
ice on cutters and drill heads. Drills have different limits and perform differently. In this comparative
study, we examine depth, pressure, temperature, pump flow and cutting speed. Finally, we compare a
few parameters of ten different deep drills.
1. INTRODUCTION
In the years 2003–06, European, Japanese and Russian
drilling teams at different sites in Antarctica and Greenland
had the experience of drilling ice under high pressure, close
to the pressure-melting point. It was a unique field experiment and an opportunity to test the performance of different
drills in such conditions, which cannot be reproduced in a
laboratory without tremendous technical effort and financial
cost. ‘Warm ice’ (unpublished data from the ‘International
Partnership in the Ice Core Sciences’ Workshop, 2004) under
high pressure (P > 25 000 kPa) seems to be problematic for
electromechanical drills. Several shallow drillings in temperate glaciers have been conducted successfully without any
special difficulty (personal communications from B. Koci and
H. Rufli, 2006). The environments in dry holes and in fluidfilled holes differ from each other, having different pressure
and ice temperature gradients. In deep holes, close to the
pressure-melting point, the main issue is that the water
produced by the heat of the cutting process refreezes. Each
drill performs differently in warm ice. Several parameters,
including cutter angle, cutting speed, pump flow, amount of
chips transported and drilling fluid, are important.
All the data presented in this paper are drillers’ data.
Some of them are approximate. Depths are drillers’ depths,
which can include uncertainty coming from depth-meter
error, cable elasticity, hole inclination and temperature
gradient. For Vostok, Antarctica, depths are derived from
ice-core measurement.
2. THE FIVE DRILLING SITES
One drilling site, the North Greenland Icecore Project
(NorthGRIP) site, is located in the Northern Hemisphere,
*Visiting engineer at Ice Core Drilling Services, University of Wisconsin–
Madison, 1225 West Dayton Street, Madison, WI 53706-1490, USA.
and the other four are located in the Southern Hemisphere
(Table 1).
NorthGRIP
The drill used at NorthGRIP is an EPICA (European Project
for Ice Coring in Antarctica) drill with the motor section and
the anti-torque section of the ISTUK drill used in the 1990s
at GRIP (Gundestrup and others, 1984). The drilling twice
reached bedrock. In July 2003, basal water rose 45 m into
the hole due to drilling-fluid pressure imbalance. The 45 m
of refrozen water were drilled out in July 2004. The final
depth was 3091 m.
EPICA DC
The drill used at Dome C, Antarctica, is also an EPICA drill,
with a motor and electronic section developed in Brasimone,
Italy, by Ente per le Nuove tecnologie, l’Energia e l’Ambiente
(ENEA; S. Panichi and others, unpublished information). The
anti-torque is from the ISTUK drill. The final depth was
3270 m, 16 m above bedrock (Augustin and others, 2007).
EPICA DML
The drill used in Dronning Maud Land, Antarctica, was the
same as at NorthGRIP. The drilling ended in January 2006,
reaching bedrock. The depth was 2774 m; basal water rose
several meters.
Dome Fuji
The JARE (Japanese Antarctic Research Expedition) drill was
used at Dome Fuji, Antarctica (Tanaka and others, 1994;
Fujii and others, 2002). The drilling reached 3029 m depth
in January 2006, and 3035 m in January 2007.
Vostok
The drill used was the KEMS-132 (core electromechanical
drill; Kudryashov and others, 1994, 2002). Drilling reached
3650 m depth in January 2006 and continued in 2006/07.
74
Augustin and others: Drilling comparison in ‘warm ice’
Table 1. Drilling-site characteristics
Location
Latitude
Longitude
Elevation (m)
Ice thickness (m)
Accumulation (kg m–2 a–1)
Mean annual surface temperature (8C)
NorthGRIP
EPICA DC
EPICA DML
Dome Fuji
Vostok
Greenland
758 N
428 W
2917
3090
175
–31
Antarctica
758 S
1248 E
3250
3280
25
–55
Antarctica
758 S
08 E
2892
2755
64
–44
Antarctica
778 S
408 E
3810
3035+
27
–54
Antarctica
788 S
1068 E
3488
3753
21
–56
Table 2. First difficulties at the drilling sites
Depth (m)
Temperature (8C)
Pressure (kPa)
T (8C)
NorthGRIP
EPICA DC
EPICA DML
Dome Fuji
Vostok
2931
–7.1
26 200
5
3119
–5.8
28 100
3.6
2670
–5
24 300
3.1
3000
–2.8
27 000
0.8
3500
–7.9
31 900
5.4
3. DRILLING PERFORMANCES IN WARM ICE
For each drilling site we compare depth, temperature,
pressure and temperature difference from pressure-melting
point (T). We also look at drill characteristics.
‘First difficulties’
What we call ‘first difficulties’ is the first remarkable penetration rate change approaching warm ice (Table 2). One of
the first signs is ice chips frozen onto shoes and cutters’
cutting edges. The JARE drill encountered first difficulties
much later than the other drills, progressing normally until
T ¼ 1.18C. EPICA drills performed differently at the three
different sites. The drill versions were slightly different and
were operated by different driller crews at each drilling site,
which probably explains the variation in T from 3.18C to
58C. The KEMS-132 drill seems to have encountered drilling
difficulties earlier, at T ¼ 5.48C. At most sites, drillers can
use change parameters like cutter head rotation speed,
cutting angles and fluid circulation to deal with the first
difficulties encountered when drilling warm ice.
First use of ethanol/water solution
At three of the sites (NorthGRIP, EPICA DC and EPICA DML),
ethanol/water solution (EWS; Zagorodnov and others, 1994)
was used to facilitate drilling (Table 3) by being poured into
the hole at the start of each run (Augustin and others, 2007).
With the EPICA drill it was used within the very short range
Table 3. First EWS use at drilling sites
Depth (m)
Temperature (8C)
Pressure (kPa)
T (8C)
NorthGRIP
EPICA DC
EPICA DML
3002
–4.9
27 000
2.8
3150
–5.2
28 400
3
2700
–4.3
24 200
2.6
2.68C < T < 38C, showing the limitations of the EPICA drill’s
capability to penetrate ‘warm ice’.
Last drilling depth
So far, drilling operations have been concluded at only two
sites, NorthGRIP and EPICA DC. At EPICA DML, refrozen
water may be drilled in the near future. At Dome Fuji, the
temperature is very close to pressure-melting point
(T ¼ 0.38C), and there are 15 m left before bedrock. With
some difficulty, our Japanese colleagues are still able to drill
without using EWS. At Vostok, the situation is affected by the
presence of the subglacial lake, the distance to which is
estimated at 105 m. Water should refreeze at the interface
(Salamatin and others, 1998). In the 2005/06 season, KEMS132 was able to penetrate into ‘warm ice’ with some
difficulty (Table 4). The data in Tables 2–4 are also displayed
in Figure 1.
Drill characteristics
We compare the flow, fluid velocity, density and cutting
speed of the four drills operated at the five sites (Fig. 2). The
JARE drill has the smallest pump flow (8.5 L min–1), and the
KEMS drill the highest (27.5 L min–1). KEMS has the highest
cutting speed (0.76 m s–1), and JARE and NorthGRIP the
lowest (0.3 m s–1). These preliminary data from field experiments show that flow and fluid velocity are not the only
determinant factors for drills to behave better in ‘warm ice’.
The JARE drill had excellent results with the smallest pump
flow. It also has a great capacity to store ice chips. The
mechanical action of the boosters inside the chips chamber
provides an excellent chip density (0.49), much higher than
that of the other drills. It will be interesting to follow the
KEMS-132 drill performance, to see how close to the
pressure-melting point the drill can go. EPICA drills have
limited capability in ‘warm ice’, as shown by the use of EWS
to overcome this problem.
Two different types of drilling fluid were used at the five
different sites. NorthGRIP, EPICA (DC and DML) and Vostok
used a two-component drilling fluid (D30 or D60 mixed with
Augustin and others: Drilling comparison in ‘warm ice’
75
Fig. 1. Drilling comparison: first difficulties, EWS first use, and last drilling depth.
141B), while at Dome Fuji a single drilling-fluid component,
n-butyl acetate, is used (Talalay, 2002). These two drilling
fluids have different effects on the cutting process close to the
pressure-melting point. Another example of a deep ice-core
drill that used n-butyl acetate and reached warm ice is the
PICO 132 mm drill used at Siple Dome, Antarctica, in 1999.
Data are not complete, but the drill reached bedrock close to
the pressure-melting point (T ¼ 1.748C). No problems
were encountered (Bentley and Koci, 2007).
4. DRILL DESIGN COMPARISON
Ten different deep drills, or more if we include all the
different versions, have been manufactured since deep ice
coring began. The first one, the CRREL (US Army Cold
Regions Research and Engineering Laboratory) electromechanical drill, was used at Byrd Station, Antarctica, in 1968
(Ueda and Garfield, 1969). Unfortunately, few data are
available for this drill, so it is not listed with the others in
Table 5. The Italian drill IDRA is still under development at
the time of writing. It is scheduled to be used for the Talos
drilling operation during the 2007/08 Antarctic season. The
Berkner drill is a short version of the EPICA drill, with a
different motor section. The ISTUK drill (Gundestrup and
others, 1984) and the PICO (Polar Ice Coring Office) drill
(Wumkes, 1994a, b) were used in the 1990s. The Deep Ice
Sheet Coring (DISC) drill, developed by Ice Core Drilling
Services (ICDS), Madison, Wisconsin, USA, tested in Greenland in summer 2006 in pure Isopar K. The very low density
value of Isopar K (0.761 g cm–3) may have significantly
affected the performance of the DISC drill. EPICA, JARE and
KEMS have already been mentioned. Drill length, core
length, ice-chip concentration and ice-chip density are
shown in Figure 3.
Table 4. Last drilling depth in February 2006
Depth (m)
Temperature (8C)
Pressure (kPa)
T (8C)
NorthGRIP
EPICA DC
EPICA DML
Dome Fuji
Vostok
3091
–2.1
27 600
0
3270
–2.6
29 500
0.3
2774
–2
24 800
0
3029
–2.3
27 300
0.3
3650
-4.9
32 600
2.4
76
Augustin and others: Drilling comparison in ‘warm ice’
Fig. 2. Drill comparison: pump flow, fluid speeds, ice-chip density and linear cutting speed.
Table 5. Drill specifications
Berkner1 DISC 20062
Drill length No. 1 (m)
Drill weight in air (kg)
Drill weight in fluid (kg)
Drill descent speed (m s–1)
Drill ascent speed (m s–1)
Rotation speed (rpm)
Hole diameter (mm)
Core diameter (mm)
Cutters o.d. (mm)
Cutters i.d. (mm)
Cutting angle (8)
Clearance angle (8)
Drill head body o.d. (mm)
Outer tube o.d. (mm)
Outer tube i.d. (mm)
Core barrel tube o.d. (mm)
Core barrel tube i.d. (mm)
Core length maximum (m)
Chips chamber tube o.d. (mm)
Chips chamber tube i.d. (mm)
Chips chamber filter (mm)
Drive shaft o.d. (mm)
Drive shaft i.d. (mm)
Screen diameter o.d. (mm)
Screen diameter i.d. (mm)
Screen length (mm)
Screen No.
Chips chamber length (m)
Pump flow (L min–1)
Motor section diameter (mm)
Electronic section diameter (mm)
Anti-torque body diameter (mm)
Average length of run (m)
6.5
160
?
0.7
0.7
50
129.6
98
129.6
98
45
10
118
118
113
104
100
2.138
114.3
110.3
N/A
30.5
20
N/A
N/A
N/A
N/A
3.213
18
?
?
?
2
14.48
404
335
1.2
2.5
80
170
121.5
170
121.5
50
15
166
N/A
N/A
157
137
4.29
151.5
128
N/A
0
0
119.8
108
760.9
8
6.09
114
127
133
127
2.49
EPICA3
JARE4
KEMS1325
ISTUK6
IDRA7
11
160
?
1.4
1.4
57
129.6
98
129.6
98
45
10
118
118
113
104
100
3.75
114.3
110.3
N/A
30.5
20
N/A
N/A
N/A
N/A
4.02
18
110
110
110
2.8
12.3
187
146
0.55
0.8
55
135
94
135
94
35/40
15
132
123
114
101.6
97.6
3.84
123
114
N/A
27.2
16.2
N/A
N/A
N/A
N/A
5.510
8.50
102
102
118
3.67
13
240
?
?
?
120
135
107
135
107
45
5
127
N/A
N/A
127
117
3
?
113
N/A
32
?
N/A
N/A
N/A
N/A
4.5
27.5
?
?
?
2.57
11.5
180
?
1
1
50
129.6
102.5
129.6
102.5
45
12
112
Channels
Channels
110
104
2.75
110
100
N/A
15
N/A
N/A
N/A
N/A
N/A
3.3
3.36
?
?
110
?
?
?
?
?
?
?
129.6
98
129.6
98
?
?
?
?
?
?
?
3
88.9
84.9
83
0
0
N/A
N/A
N/A
N/A
4.1
?
?
?
?
?
NorthGRIP8 PICO1329
11
150
?
1
1
50
129.6
98
129.6
98
45
10
118
118
113
104
100
3.75
114.3
110.3
N/A
30.5
20
N/A
N/A
N/A
N/A
4.02
18
?
?
110
?
25
625
?
?
?
100
181
132
?
?
45
15
?
?
?
?
?
6
?
?
?
?
?
?
?
?
?
?
105
?
?
?
?
Notes: o.d.: outer diameter; i.d.: inner diameter. Question marks indicate uncollected or unknown data. N/A: not applicable.
Data sources: 1Personal communication from O. Alemany (2006). 2ICDS. 3Augustin (unpublished information). 4Tanaka and others (1994); Fujii and others
(2002); Motoyama (unpublished information). 5Kudryashov and others (1994, 2002); Talalay (unpublished information). 6Gundestrup and others (1984);
Hansen (unpublished information). 7Personal communication from S. Panichi (2006). 8Hansen (unpublished information). 9Wumkes (1994a, b).
Augustin and others: Drilling comparison in ‘warm ice’
77
Fig. 3. Drill design comparison: drill length, core length, concentration and ice-chip density.
It is interesting to look at two drill parameters, Rd (Rd =
core barrel length/drill length) and Rda (Rda = average core
length drilled/drill length). Rd varies from 0.24 (PICO) to
0.34 (EPICA), while Rda varies from 0.16 (DISC) to 0.31
(Berkner). The ratio Rd is one of the most difficult parameters
to determine in drill design, as one cannot know in advance
how dense the ice chips inside the ice-chips chamber will
be. Another interesting parameter is the concentration of ice
cuttings, c (percentage of the ratio of the ice volume cut by
the volume of the chips chamber), inside the chips chamber,
as defined by Talalay (2006). For the nine drills, c varies
from 73% (IDRA) to 38% (KEMS). KEMS’ designers were
very careful, designing a long chips chamber giving a 38%
concentration for their drill, while IDRA’s designers have
been very optimistic, as the concentration cannot exceed
63% (Gardner, 1994, cited in Talalay, 2006).
The ice-chip density inside the chips chamber can be
checked during the drilling operation. If we call the design
density Dd, calculated from the ice cut weight for the
maximum possible core length, and the average density Da,
calculated from the ice cut weight for the average core
length obtained in the drilling operation, Dd varies from
0.39 (Berkner) to 0.67 (IDRA) and Da varies from 0.30
(DISC) to 0.49 (JARE). The Da obtained by the JARE drill is a
maximum that can be reached inside a chips chamber. The
density of ice chips inside a chip chamber depends on
several factors such as chip size and chip shape, which
themselves depend on cutting angle, cutting speed and ice
structure. Studies of ice-chip structure would be very useful.
The density of ice chips inside the chips chamber also
depends on the ability of the fluid circulation and filtering
systems to compact chips inside the chips chamber. Therefore it is not possible to calculate, at the time of the drill
design, the ice-chip density that will be reached inside the
chips chamber. The real ice-chip density value is known
after the production of the first cores. History shows that very
often designers are too optimistic and expect longer cores
than the drill (ice-chips chamber capacity) allows. How
densely the drill is able to pack the chips inside the chips
chamber is an important issue.
5. CONCLUSION
Data collection is incomplete, but we have some good
information and possible tracks for drill design. The amount
of ice chips produced, ice-chip transportation and storage
are important factors in drill design. These factors directly
affect the length of the drill, and therefore the speed of
descent of the drill, which will have a direct impact on the
duration of the whole drilling operation. The JARE drill is the
most efficient in terms of ice-chip density; the mechanical
action of an Archimedes screw located at the lower part of
the chips chamber seems to be more efficient than the
greater pump flow of the KEMS drill. Some uncertainties
remain about how to overcome the problem of drilling warm
ice, concerning the importance of pump flow and drillingfluid type. For most drillers, a large pump flow is a positive
thing for pushing forward the limit of an electromechanical
drill in warm ice, especially if cutting speed and pump flow
can be driven independently, as permitted by the DISC drill.
Nobody yet knows how far the limit of electromechanical
drills in warm ice can be pushed. Experiments in natural
temperature, fluid and pressure conditions can only be
carried out on site, so it may take the drilling community a
few more years to answer this question. Funding agencies,
principal investigators and project partners should be aware
of the difficulty of the task. This issue, arising at the very end
of the project, should be resolved while drillers are still
producing cores. This leaves very little room for tests and
experiments, especially when, as tends to be the case,
projects are running out of time and funding and the drilling
teams are tired.
78
ACKNOWLEDGEMENTS
We thank all the institutions and funding agencies of the
different projects who have given this generation of drillers
the unique opportunity of having all these deep-drilling
projects take place within a few years. We warmly thank all
the participants in the different drilling projects who have
enabled these data to be collected and made this comparative study possible. This work is a contribution to the European Project for Ice Coring in Antarctica (EPICA), a joint
European Science Foundation/European Commission scientific programme, funded by the European Union and by
national contributions from Belgium, Denmark, France,
Germany, Italy, the Netherlands, Norway, Sweden, Switzerland and the United Kingdom. The main logistic support was
provided by Institut Polaire Français–Emile Victor (IPEV) and
Programma Nazionale di Ricerche in Antartide (PNRA) (at
Dome C) and the Alfred-Wegener-Institut (at Dronning Maud
Land). This is EPICA publication no. 203. Additional funding
support was provided by the FP6 STREP EPICA-MIS.
REFERENCES
Augustin, L., S. Panichi and F. Frascati. 2007. EPICA Dome C
2 drilling operations: performance, difficulties, results. Ann.
Glaciol., 47.
Bentley, C.R. and B. Koci. 2007. Drilling to the beds of the
Greenland and Antarctic ice sheets: a review. Ann. Glaciol.,
47.
Fujii, Y. and 25 others. 2002. Deep ice core drilling to 2503 m
depth at Dome Fuji, Antarctica. Mem., Natl. Inst. Polar Res. 56,
Special Issue, 103–116.
Augustin and others: Drilling comparison in ‘warm ice’
Gardner, M. 1994. Matematischeskic golovolmki i razvlecheniya
[Mathematical puzzles and dimensions]. Moscow, Onyx. [In
Russian.]
Gundestrup, N.S., S.J. Johnsen and N. Reeh. 1984. ISTUK: a deep
ice core drill system. CRREL Spec. Rep. 84-34, 7–19.
Kudryashov, B.B., N.I. Vasiliev and P.G. Talalay. 1994. KEMS-112
electromechanical ice core drill. Mem., Natl. Inst. Polar Res. 49,
Special Issue, 138–152.
Kudryashov, B.B. and 9 others. 2002. Deep ice coring at Vostok
Station (East Antarctica) by an electromechanical drill. Mem.,
Natl. Inst. Polar Res. 56, Special Issue, 91–102.
Salamatin, A.N., R.N. Vostretsov, J.R. Petit, V.Y. Lipenkov and
N.I. Barkov. 1998. Geophysical and palaeoclimatic implications
of the stacked temperature profile from the deep borehole at
Vostok station, Antarctica. Mater. Glyatsiol. Issled./Data Glaciol
Stud. 85, 233–240.
Talalay, P.G. 2006. Removal of cuttings in deep ice electromechanical drills. Cold Reg. Sci. Technol., 44(2), 87–98.
Talalay, P.G. and N.S. Gundestrup. 2002. Hole fluids for deep ice
core drilling. Mem., Natl. Inst. Polar Res. 56, Special Issue,
148–170.
Tanaka, Y. and 6 others. 1994. Development of a JARE deep ice
core drill system. Mem., Natl. Inst. Polar Res. 49, Special Issue,
113–123.
Ueda, H. and D.E. Garfield. 1969. Core drilling through the
Antarctic ice sheet. CRREL Tech. Rep. 231.
Wumkes, M.A. 1994a. Development of the U.S. deep coring ice
drill. Mem., Natl. Inst. Polar Res. 49, Special Issue, 41–51.
Wumkes, M.A. 1994b. Operational considerations of the U.S. deep
coring ice drill. Mem., Natl. Inst. Polar Res. 49, Special Issue,
52–56.
Zagorodnov, V.S., J.J. Kelley and O.V. Nagornov. 1994. Drilling of
glacier boreholes with a hydrophilic liquid. Mem., Natl. Inst.
Polar Res. 49, Special Issue, 153–164.
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