17 July 2009

Working with the shallow cores

Zoe and Kaitlin with the shallow cores

Zoe and Kaitlin working with the shallow cores at the firn village.

At the firn village we have Zoe and Kaitlin who are interested in the ice cores from the shallow drilling – not the borehole as the gas pumping gang is. The shallow core are carefully documented and logged and packed in bags and boxes for transport back to the US. Every day the cores are transported back to camp and stored in the colder science trench.

What we have done today:
1.Drilling with the NEEM long drill: 7.67 m. Drillers depth: 1181.59m
2. Logging 95.78 m of core. Logging depth 1028.27 m
3. CFA analysis: 19.80 m. Depth: 429.55 m.
4. Maintained saws and placed bags for the processing under the brittle zone in the science trench
5. Made ventilation from CFA-lab directly to the surface to further cool the science trench and to lower the temperature in the CFA-lab from 30-40°C to 23°C.
6. Shallow drilling at the air-firn village. Present depth 30 m. Air-sampling has been made at the depth 30m.
7. Shallow drilling at a second site 40 m from the firn-gas sampling borehole. Present depth 6.6 m. 
8. Temperature logging of the 2008 shallow hole started
9. Pit sampling by Zoe and Kaitlin.

Ad.1: Driller’s Report July 17, 2009: “The last night shift and morning shift were spent doing thorough maintenance on the drill. In between was an unexpected midnight shift to recover a lost core barrel down hole.
Drilling performance had become unsatisfactorily unstable so we did an “overhaul”.  We replaced all seals on the pump and valves and serviced the pump.  We replaced the black PE guides near the drill head.  We separated the outer tubes and found that ice had collected around the inner sleeve that needed to be melted out.  We repositioned the central booster just below the hallow shaft junction. The drill head was inspected and the cutters were changed back to the old set, sharpened, and the pitch retuned.  We learned that the cutter sets do not have exactly the same dimensions.  The new set we had put on at 1030 meters gave a very slightly smaller diameter, one that allows the drill to pass with the previously used cutter set, but that increased friction enough to rotate the inner core barrel backwards and disengage the super banger when descending the last 150 meters of the borehole.  Happily, the resulting fishing expedition for the lost core barrel was successful on the first attempt.
Subsequently the drill was reassembled and the lower part of the borehole was reamed with the “old” very slightly wider cutters.  Two runs before dinner were excellent and stable throughout.  Inclination is now 2.38. “

Weather: A very nice and sunny day with blue sky and  night temperatures between Thursday and Friday down to -10°C and day temperatures up to -5°C. Wind 3-12 kn from S.

FL, Dorthe Dahl-Jensen

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