Wednesday, October 22, 2014

DFDP-2 @ 360 m: solid rock since 240 m

Rupert Sutherland, GNS Science
John Townend, Victoria University of Wellington
Virginia Toy, University of Otago

A lot has happened since our last update. We have completely reorganised the site and positioned a new drill rig over the borehole. We’ve tidied up all the big steel pipes, and the Washington Drilling trucks, rig, and drillers, have left. We’ve hoisted the flags on our science facility and are getting down to some serious business in solid rock.

Onsite science facilities 22/10/14. Photo R. Sutherland.
The main phase of open-hole drilling began at 3 pm on Sunday 19 October, and we had reached 360 m depth by 7 am this morning. Our rate of progress varies between 1 and 4 metres per hour. We are now working in shifts around the clock.

The geology group is collecting rock cuttings made by the drill bit and transported to the surface entrained in the drilling mud. The mud travels down the centre of the drill pipe, out through the bit, and back up to the surface. It emerges at 25°C, but we know from downhole measurements that the temperature at the bottom already exceeds 50°C.

8.5” PDC drill bit. Photo: R. Sutherland.

We have three main science tasks at the moment. The first is to document drilling rates and mud characteristics. These measurements tell us about rock properties, fluid pressures and downhole temperatures. The second is to use wireline tools to survey the borehole during breaks in drilling. Finally, we are carefully analysing the rock cuttings to determine when to stop this phase of open-hole drilling and to start collecting rock cores.

Drill rig and mud pump 22/10/14. Photo R. Sutherland.

Primary funders of the DFDP-2 project are: the International Continental Scientific Drilling Program (ICDP), the Marsden Fund of the Royal Society of New Zealand, GNS Science, Victoria University of Wellington, and the University of Otago.

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