Hot Water Drilling Manual
- to be used on Fimbul Ice Shelf, January 2010
Ole A. Nøst, Per G. Gabrielsen & Lars H. Smedsrud
Keith Makinson and Keith Nicholls from British Antarctic Survey hot water drilling
the Filchner Ronne Ice-Shelf. This manual is solely based on their experience.
1.0 Equipment
Here we describe the equipment to be used in a setup for drilling through the
Fimbul Ice Shelf. The planned holes are from 250 to 450 m deep. How the
equipment is set-up on the ice shelf, and the drilling sequence will be described
in the next section.
1. Flubber (Water tank)
The flubber is a large flexible rubber water tank that is to be placed in a shallow
snow pit with flat bottom. There is a sheet of the same material that should be
used below to protect the flubber, and insulation (~2.5 cm thick) shall be placed
underneath these two. It is important that the bottom of the snow pit is flat and
level, otherwise it will start tipping over. The flubber can be filled to a maximum of
about 12 m3 of water. Snow for the flubber should be taken from an area
radiating out from the flubber, but do not dig further down than 0.5 m, as this will
make walking difficult in the area. We could use skidoo sledges for transporting
snow to the flubber.
2. Pumps
There are three CAT pumps powered by diesel engines. We plan to use two at a
time, and have one spare. We could however complete the drilling using one
pump, but it would take longer. The pumps are to be set up as sketched on
Figure 1. We have packed the pumps together with the hoses that will connect
the flubber, the pump and the heaters. We have spare parts for these pumps,
extra engine oil, hydraulic oil for the pump, air and oil filters.
3. Pressure valves and pulsation dampers
These are connected straight after the pumps. The pulsation dampers will even
out the pressure pulses from the CAT pumps, and the pressure valves release
the pressure if it gets too high. We plan to operate with about 50 bar when
drilling, the security valve should then be tested and set at 70 bar.
Picture shows Lars
Henrik connecting the
security valve and
pulsation dampers.
4. Pressure and flow meters
Pressure sensor and flow meter are connected like shown on the picture below.
The maximum flow from each water pump is around 38 litre per minute. The
relative flow should be adjusted at the valves of each heater so that the outlet
temperature on each heater is approximatly the same. The drill speed formula
needs flow to calculate optimal speed, but the added flow from the two pumps
are also measured at the drum.
5. Heaters
We have 8 heaters. The smallest one should be used in the circuit from the
submersible pump, sending warm water down the pump hole. All heaters should
be placed on wooden beams, to prevent them melting down into the snow. We
will burn air-fuel and it is OK to burn the standard oil that NP has to transfer this
air-fuel to diesel. This oil is added as 1% in the fuel drums to lubricate the fule
pumps. The heaters run best at 80ºC but stay below 90ºC to avoid damage to
hoses. Spare parts are electric igniter electrodes.
6. Flow control valves
These valves control the flow back
to the flubber, or send it to the
drum when drilling. It can also be
used to isolate one circuit of
heaters when starting to melt
snow, or anti-freezing.
It is also good to let the air out of
the heaters and hose when starting
up.
7. Temperature, flow and pressure sensor at drum
These sensors are connected to the hose at the drum like shown below. These
values are used in the drill speed formula to calculate optimal speed on drum.
8. Sensor-display
The display boxes are placed in a big zarges box and shows data from the
sensors in (7). Additionally the display show drill speed and drill depth from the
sensors on the capstan (11) and the water level sensor placed with the
submersible pump (12). The display can be connected to an alarm. The alarm
should be used on the water sensor when we approach the ice base, but can
also be used to indicate too low/high temperature, pressure and load when
drilling. We will hold back the sensor display box, and bring it with us when we fly
to Troll in December 2009.
9. Drum
The hose connects to the drum like shown in the pictures below and above. The
drum rotation is controlled by a yellow hydraulic engine. To get enough hose on
the drum we need to lay it very neatly on the drum after it has been assembled.
The drum also stands on wooden beams and insulation as it also gets warm
during drilling.
10. Capstan
The capstan is placed on two 5 m
long 10cm×10cm wooden beams.
It is further described in the
sequence section later. Sensors for
drill speed and drill depth, as well as
hose tension are connected to the
display unit (8).
11. Nozzle and submersible pump.
We have three nozzles. Two thin ones to drill the hole. One reaming nozzle to
enlarge the hole has a diameter of 17 cm. This is the same diameter as the
Aanderaa frames we will deploy. This should not be a problem, as there is
significant melting after the reaming nozzle has passed a certain depth on the
way down from the warm water rising in the hole.
We should make a spare for the reaming nozzle. We plan to build a "tube" to add
to one of the drill nozzles. Also change the "jet" to one that spreads the water
outwards in this case, with NO forward pointing spray. The nozzles should be
secured using a special knot. The name of this knot is "prusik" in Norwegian.
We have three submearsable pumps, two new ones, and one old. They come
with a control box (starter) each. One of the new start-boxes needs repair. These
pumps should be strengthened using two metal rods or a metal tube to prevent
the breakage of the pump/motor coupling.
12. Hose from submersible pump.
This consists of two hoses; a yellow one for water pumped up, and a black one
for heated water going down to prevent freezing around the pump and hose in
the hole. Water is taken from the top of the yellow hose, controlled by the return
valve (13), and some is passed through a heater before it goes back down the
black hose with the remainder going to the flubber.
The power to the pump winds around the yellow and black hose as a plait.The
water level sensor is attached seperatly just above the submersible pump using
elastic string, and the cable for this is only attached an elastic rubber string at the
surface, as the hoses will stretch when they are filled with water.
13. Returnvalve.
The valve divides the water into the small heater for return down the black hose
as noted in (12). It should be easier to regulate the flow using a needle valve
rather than a "sphere" valve" as we used in the image below. The flow should be
adjusted so that the heater warms the water "significantly" to 40-80ºC but tis
depends on the water flow and heater fuel pressure.
14. Generators
Two red generators produce electrical power for heaters, electric hydralic
engines, and other instruments. We have changed filters and oil, and both are
now working properly.
15 Hydraulic power units
We have bought a new electrical engine for the blue hydraulic power, and an
altogeather new unit. Both these have two outputs, creating hydralic pressure for
the drum (9) and the capstan (10). We thus have a spare unit, and also bring the
single yellow unit.
2.0 Setup
The equipment setup should be done as shown in the sketch.
3.0 Sequence
When the position of the bore hole is decided, the average wind direction will
decide the layout of the camp. Heaters must be at the lee side of the wind so the
exhaust is blown away from the camp. The wind breaks are placed to give
maximum shelter for the equipment and ourselves. The rest is layed out as on
the sketch below. There should be free way along 0 and 180 degrees away from
the hole. The snow will be taken from the sector around 270 degrees, and should
be kept clean. This can also be our supply of drinking water. Living and kitchen
quarters should be more than 100 m away and along 45 degrees into the wind,
this will give the most the lowest noise level. A work tent can be placed near the
CTD winch if required.
The main hose(s) should be rolled neatly on the drum after its assembly. A way
to do this is to dig a hole in the snow, place wooden beams at either side, and roll
the wooden drum with its axis at ground level and freely rotating. Make sure that
the hose is on the top side of the drum when looking from the capstan.
Sketch of the drill site. The front page image is taken looking towards the flubber
on the sketch, and the living quarters would be off the upper right corner.
Time frame for the drilling is roughly three weeks at first site;
~ 2 weeks for preparing to drilling first hole
~ 2 days drilling
~ 1 day CTD / mooring deployment + 1 day rest
Preparation: water and pump
Generally, pumps, heaters,
and fuel drums stand on wood.
This will stop them from tipping
over and melting into the snow.
Hoses needs to be insulated
and additionally placed on
insulation sheets as shown in
the image to the right.
We start off by placing the stainless steel tank near the side of the flubber. The
melt tank base gets very hot and needs to stand on metal rods ontop of a
wooden board to stop it melting in. We mount the oil burner and shovel in snow,
and fire up. When the tank is full of melted snow we transfer the water over to
one of the plastic tanks to make up a mixture of antifeeze and water to the
correct strength, using either a bucket or the small blue electic ‘Handy pump’.
Next, water is transferred to the other plastic tank standing inside the flubber. We
carry on shovelling more snow into the melt tank until we have enough water to
make it go through a pump and a heater. We make a curcuit from the black
plastic tank, to a pump, to a heater, and back to the plastic tank. We can then
heat up the water in this tank, and throw in snow that will melt inside it. As it fills
water starts overflowing the plastic tank and into the flubber. Once the water level
in the flubber is deep enough we can remove the plastic tank and circulate water
directly to and from the flubber. Note that hoses must be supported over the side
of the flubber to prevent pressing down of the side, causing loss of water and
melting under the flubber!
The number of heaters can be increased if needed to speed up the melting and
digging! They should run at about 80ºC. If they get up to 90ºC the thermostat
should turn them off. We continue until the flubber is close to full. We now have
more than 10m³ melted water (10000 l). This is more than enough to make a 60
m hole. Using 38 l per minute this water would last for over 4 hours of pumping.
When we finish melting, turn off the heaters and anti-freeze the system.
Using the antifreeze mixture we pressure test the hoses and heaters and the
pressure release valves. Check that the security valve works, and that there are
no leaks. Check that the insulation covers everywhere as leaks may be hidden.
Test all the drill system pumps and heaters with antifreeze so that if serious
problems arise, freezing pipes, hose, valves, pumps etc. are not a problem.
When antifreezing the whole hot water drill system do it in small parts. Pump
antifreeze through one circuit of heaters only and watch the outflowing water as
we pump, and when it changes to blue color place the out-hose back into the
plastic tank. Then blow out the ant-freeze
from this set of heaters using airpressure. Antifreeze the next heaters
circuit also, and empty into the plastic
tank. If the submersible pumps have
been used, pour a little anti-freeze into
both submersible pumps as well until it
runs out of the intake. This liquid will be
lost. After we have started drilling we also
need to ant-freeze the drilling hose. This
then requires pumping antifreeze into the
hose for as long as we can. As we run
out of antifreeze, we stop the pump. Blow
the liquid through the entire drill hose
using airpressure. Remember the
antifreeze mixture will always get weaker,
check it regularly and add extra
antifreeze as required.
Preparation: Hole
We start this by digging a narrow trench up to 1.5 m deep. The capstan is placed
above this ditch on 10cm*10cm wooden beams to make a stable platform. At the
bottom we place a ready made board of plywood. The drilling will start through
holes in this plywood board.
The trench makes it alot easier to deploy and recover instruments and hoses.
The hose to the submersible pump passes over an empty fuel drum, insulated
both at the bottom and behind. This prevents the hose from melting/digging into
the snow. (The drum will also get warm from sunshine).
The setup of the capstan and the hole is shown in the sketch to the right, and
also in the images below.
Check that the instruments on the capstan works; load and drill speed, as well as
drill depth. We make a10m mark on the drill hose, to know it is soon to appear at
the surface.
We will soon start drilling in
the hole at the middle the
buried and insulated fuel
drum. We will drill quickly in
the beginning. The upper
snow layer is loose anyway,
and we do not want to make
a big hole and loose alot of
water. Otherwise we will
use a formula to set the drill
speed, based on water
temperature and flow, and
the depth we are at the
moment.
Mount the drill nozzle on the
snow infront of the capstan,
and lower it down when it
has been mounted properly.
It shall then hang freely
suspended below the
capstan. We need to able to
adjust the capstan and the
plywood board (Directions
mentioned is 0 to 180
degrees for capstan and 90
to 270 degrees for plywood
board.)
We fire up the 8 heaters and are ready to drill the first test hole.
Drilling of test hole
This hole may be drilled down to 30 m using a cone spray on the nozzle and
reamed to make a first drill hole. We can then stop drilling and take a rest,
because we have only drilled in the firn layer. This firn layer will not refreeze, and
the water we use is lost anyway. Drill quickly in the beginning, and use the
formula when we get deeper. The 30 m hole should not take more than an half
an hour to drill and 15 minutes to ream using the full drill system. Check the
depth in the display box (8). This hole will become the return hole where we
deploy the submersible pump.
At this stage the flubber can be refilled ready for the main drilling work and the
drill system antifeezed, including the drill nozzle.
Note: When using hoses intermittently always clear the water and use some
antifreeze. If a hose is ready for use next to a valve,e.g. to divert flow, and the
valve leaks even a little, the hose will become frozen, so if possible only connect
‘empty’ hoses when needed.
Final preperations and practice mooring deployment
Using the 30 m test hole practice the deployment of the submersible pump, CTD,
and mooring to ensure methods are correct and all people know what they are
doing, next time they could be very tired! Install any snow anchors that will be
needed to secure the submersible pump, mooring, capstan, CTD winch and get
all fuel, equipment and spares ready before the main drilling takes place.
We lay the black/yellow hose and the power cable (umbilical) out on the ice in
direction 0 degrees. We could use the skidoo to drag it out, and secure it with
also. Measure and mark depths on submersible pump umbilical so the
deployment depth is known, similarly, do the same with the mooring if required.
Test the CTD and the CTD winch, and finally check the instruments and lay them
ready assembled out on the snow.
Before starting drilling get a full nights sleep. For deeper drilling shifts must be
decided, as people need have some sleep. At this stage it is smart to wait for a
good weather forcast (call Rothera). When we continue from here there is "no
way back". If we have to stop the drilling operation the hole will freeze over with
~1cm per hour. We will loose the water inside the hole, and have to start melting
snow again.
Drilling of pump hole
We continue drilling using the test hole until we are at 60 m. We then make
another mark on the hose, and bring the drilling nozzle back up. We close the
water flow down the hose at 10 m depth to prevent making a big hole below the
capstan.
General check procedure during drilling every 15-30 min;
Measured Temp and Press on Drum. ~80 ºC, 50 bar
Drilling speed. To be reduced as we go deeper according to formula.
All heaters working and at similar temperature ?
Leaks ? (Water, oil, fuel)
Return flow to flubber (should pour in making small water fall)
Heat inflow to sub-pump, change temp by regulating flow to heater.
Generators and Pumps (Diesel level)
Refill drums from back using 1 hand driven mechanical pump and new drums.
Water level above the submersible pump (+2 m).
Ream the hole and deploy pump
Attach the reaming nozzle and antifreeze the first drill nozzle. We use this reamer
in the same way, drill fast in the beginning and then slow down gradually. The
reaming goes faster than the drilling because it only checks the minumum hole
diameter.
Back on the 60 m depth mark with the reaming nozzle, we shall make a big ice
cavern. This cavern shall be large enough so that when we drill the other hole at
the side water shall connect through from the deeper main hole. Leave the
reaming nozzle at this depth for up to 20-30 minutes. Make sure the water level
in the flubber is not less than ~ 25 %.
As the reamer nozzle is left at 60 m depth we prepare the submersible pump.
When the pump hole is finished we bring the reaming nozzle back up. We can
place the hose inside the flubber, and leave the pump running. Secure the hose
carefully because at high flow rates it can ‘jump out’ of the flubber. The heaters
should be stopped before we start lowering the submersible pump.
The pump is secured and lowered slowly down the hole. The water level sensor
cable is lowered by hand at the same time. We need to be very careful at the
end, as it grows heavier and heavier. Using the skidoo, or maybe the band
wagon to secure it with is good. When it has reached the correct depth we use
the rope (Yalegrip) attached to the hose and secure it to the prepared snow
anchor.
When everything is placed and connected we start the electrical pump by
switching it on in the starter box. The water will start flowing up through the
yellow hose, and some of it shall be heated and sent back down the black hose.
Now secure the water level sensor cable using elastic string at the top of the
hole. Keep on pumping warm water back down the hole while we fill the flubber.
This may take some time, also have a small rest.
At the pump there is a pressure sensor, measuring the water level above. Make
sure that there is always some water above the pump (2-3 m minimum). The
return water to the flubber should pour in from above water level so that it makes
a small waterfall. In this way we hear it flowing all the time, and can see if it
stops. If this water stops flowing, first check the power and try to restart, if no
restart we need to bring up the pump quickly. Be very careful not to snap the
pump at the top of the hole, lift last 5-10 m by hand.
Change the nozzle to the drill nozzle and move the capstan over to the other hole
in the plywood board. If the flubber becomes full or the water level becomes too
low in the hole, we stop the return flow to the flubber and divert all the flow back
down the hole through the heater.
Drilling of main hole
Using water from flubber we start drilling the main hole. We drill slower and
slower with depth using the formula. We drill down again to the 60 m depth mark,
and hold the drill there for a short time, then bring the drill nozzle back up.
Remember to stop water flow at 10 m depth. During this drilling the water level
can suddenly increase in the pump hole if a connection is made between the two
holes higher in the hole.
We change nozzle, and ream the main hole down to the 60 m, the level where
the pump is hanging. We should have a connection between the two holes now,
and see the water starting to fill up again on the water level display. Otherwise
we may leave the reamer at this depth for longer. But with time the connection
will open up driven by the warm water ascending inside the hole.
Bring up the reaming nozzle. Change to drill nozzle, and resume drilling from 60
m depth. We switch on the full flow when the drill nozzle is approaching the water
level depth, 60 m less the water level recorded in the pump hole. Open up the
return flow to the flubber as we start drilling.
We continue drilling. If the water flow is stopped for some reason we need to
bring up the drilling nozzle at once by at least 10 m. It could freeze the nozzle tip
very quickly.
From the seismic data we have a good estimate on total ice thickness at the site.
When we approach this depth we set the alarm on the water level indicator for
+/- 20 cm. This sensor tells us how much water there is above the submersible
pump, and it will change when we drill through the ice shelf. The water level
could either drop or rise, but it will be a permanent and signficant change. For ice
250 m thick the fresh water level in the hole should be around 39 m and 55 m for
ice 450 m thick.
Stop drilling immediately, and mark the hose at this depth using tape. We bring
the nozzle 1 m back up and leave it for 10 minutes. This will help making a better
transition for the CTD entering the hole from below. We also run the nozzle a bit
up and down to widen the opening.
Then bring the drill nozzle up, and change to the reaming nozzle. We then use
the reamer mainly to check the hole diameter but also to enlarge the main hole a
little as the first drilling should have made the hole the correct size. Once the drill
is recovered from the hole we antifreeze the hoses and heaters, and are ready
for the CTD.
Note: It should be possible to leave the submersible pump running and just
recirculate water through the heater during the CTD work. But with a long 60 m
power cable next to the CTD cable this may interfer with its communications and
the pump must be turned off. In this case, antifreeze the surface hoses and pour
about 5 litres of antifreeze down both hoses to the submersible pump.
CTD measurements
We deploy the CTD using the anchored CTD winch. The CTD wire runs over a
metered wheel on the capstan before it descends the hole. Ropes with snow
anchors secure the capstan on opposite side to the CTD winch. We do a good
number of CTD profiles, and try to get it back up the hole. If it gets stuck, we do
not pull very hard, but bring it back down and profile some more. A different
directions on the tides will hopefully make the next attempt more succesful.
In the worst case we need to cut the CTD cable but as a final try, use the split
metal rod to slide down to the CTD to try to release it. It is not possible to drill
with the CTD in the main hole as the CTD wire and the hose will get entangled,
and we risk loosing both the CTD and the hose/nozzle. The hole is freezing over
quite slowly. The reamer makes at least 17 cm diameter hole, and refreezing is
not more than about 1 cm in diameter every two hours. So we can keep on taking
CTD profiles at least 12 hours (equals loss of 6 cm in diameter).
Rig deployment
We start everything up once again and ream the main hole once more. After the
big nozzle is back on the surface we need to antifreeze the for a last time.
We then deploy the current meter rig that has been ready ever since we started
drilling on the ice. We need to be careful, drop it nice and slow, avoid long stops
because of freezing, and make sure it is secured all the time on the way down.
Using the skidoo as an "anchor" and drive slowly towards the hole is a good idea.
At the right depth we secure the rig to a snow anchor, and leave wooden beams
(4"×4") across the hole to hold the rig. We remove the capstan and the let go of
the skidoo.
Setup the mooring logger as soon as is possible so that if failures occur some
data will have been collected. If the mooring fails is will be difficult to recover,
even immediately, but after an hour or two it is likely to be impossilbe because of
refreezing of the hole.
We then have to bring the submersible pump up slowly using the skidoo. The
pump and the single heater have been running until now, because our main
priority was to get the rig deployed. When the pump approaches the surface we
need to be very careful to not break the pump (but it has been strengthened
using metal bars). Suggest lifting the last 5-10 m by hand to avoid breakages.
We antifreeze both hoses and empty with air pressure. Pour anti-freeze liquid
directly in the outflow connector on the pump to antifreeze that.
Rest
At this stage we will have worked intensively for 2 weeks, and not slept much the
last 24 hours. It is therefore very important to take a proper rest. Shifts and/or
rest periods are recommended for drilling the deep hole. Take a day off, and
relax as much as possible. We should be very happy if everything has worked as
planned.
BAS hot water drilling shift pattern with 4 people. This will provide 3 people on
site at all times with long handovers and lots of cooked food available:
Each person has: 6 hours sleep, 3 hours – make food/rest, 12 hours work, 3
hours – make food/rest.
Packing
Everything is dis-assembled and packed in boxes. However, we keep as large
parts of the drill intact as possible, and make the most of the big snow cats and
their trailers. We drain the left over water from the flubber, and role the hoses
back on the empty wooden drums in the snow pits. GPS positions are double
checked.
We then mark the hole with flags and tall poles. We want the current meters to
operate for many years, and there is roughly 0.5 m/year snow accumulation.