Both drilling operations are progressing very well – University of Copenhagen

19 May 2015

Both drilling operations are progressing very well

The Air Greenland helicopter taking off from camp.

The Air Greenland helicopter taking off from camp.

We still suffer from rather short workdays due to high day temperatures and the effects of turning around our working day, but the core quality is excellent for both the main and shallow drilling, and we have not encountered any significant problems with either.

The run-in of the long Hans Tausen drill continues, and all morning, we produced cores of approximately 1.4 meters’ length on a routine basis. Later in the day, the cores started to show signs of stress due to the pressure difference between the hole and the surrounding ice. At this time, we had drilled to about 132 meters, and the pressure difference ice and hole was about 10 atmospheres.

The pressure difference makes the cores crack already when is being drilled, and the core breaks start to be less regular. The cure for this is to go to wet drilling, where the hole is partially filled with a liquid that partially balances the pressure difference.

The trick is to find a liquid that satisfies a lot of different technical and scientific criteria, and our group has put a lot of effort into identifying and testing different alternatives.

The main requirements are that it should have roughly the same density as the ice (917 kg/m3), stay liquid at the temperatures inside the ice sheet (around -18°C where we are now), have a high viscosity, be hydrophobic, not be environmentally hazardous, not be too expensive, and finally (but of course very important), it should not interfere with the measurements that we are making on the ice core.

We use Estisol, which is a low-molecular-weight fatty-acid ester. Adding the liquid immediately removed all signs of stress, but the price is clear: Drilling with liquid is a messy and smelly business and staying warm while handling the cold liquid is a challenge.

Logged length 133.02 meter.

We are at a depth of 35 meters in the second shallow drilling. Everything is going well.

Todd Sowers has been taking amazing movies with his remote-controlled drone, which decided to fly away from home today. At an altitude of about 1000 ft, it lost connection to the controller and slowly drifted away.

In the evening, we received a few supplies by Air Greenland helicopter, and had to say “see you later” to a colleague who had to return early for family reasons.

Weather: The weather cleared up and in the morning, and the skies were clear for some hours, allowing for the helicopter to arrive. Clouds rolled in during the day, but the weather is still much more pleasant than during the last few days.

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