Tuesday, November 25, 2014

DFDP-2 @ 547 m, drilling equipment

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

DFDP-2 drill site from the bridge over Whataroa River.13/11/14. Photo R. Sutherland. 
Exploration can present logistic challenges, because any trip into the unknown may hold surprises. In the case of our drilling experiment, the challenges we face include: having the right drilling equipment; attracting and sustaining a strong team of people for many months; and extracting scientific results from challenging underground conditions (e.g. the high temperatures that we have already encountered).

Obtaining and maintaining the right drilling equipment has proven tougher than expected and we are now several weeks behind schedule.

The current drilling method we are using breaks the rock into small pieces (cuttings) and creates a 215 mm diameter open hole. It is a similar method to that employed by the petroleum industry, but we are drilling into a much harder rock than they typically encounter. Hard rocks similar to our site are commonly drilled by mineral explorers (e.g. gold miners), but they usually collect rock cores and drill a much smaller (<125 mm) and shallower hole. It is hard to find a drilling company with such overlapping experience. The NZ contractors we have on the job (Webster Drilling and Eco Drilling) have been very helpful and are learning with us.

This video shows you what the business end of our open hole drilling gear looks like:

We reached 547 m depth last Wednesday (17/11/14), but progress was slow and equipment was damaged. A decision was made to remove all drilling equipment from the hole, send it to Christchurch for a makeover, and obtain new specialised drill bits. The new roller-cone drill bits have hardened points to shatter the rock, but they need several tons of weight on them to be effective.

We hope to start drilling again tomorrow.

Photos of different (used) drill bits: 
(A) Coring drill bit with industrial diamonds for hard rock
 – the hole in the middle is where rock core enters; 

(B) PCD, Poly-Crystalline Diamond, bit for an open hole;
(C) Roller-cone bit designed for soft rock (damaged bit).
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.