DFDP-2 @ 850 m, mylonite, borehole shape

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

Are we there yet?  They were born when we started and are growing up fast. 5/12/14.  Photo R. Sutherland.

 It was a slow start yesterday as the reconditioned drill reamed its way into the hole, but by this morning we were making new hole and producing fresh rock cuttings. We are now making about 3 m of new hole every hour and passed 850 m at lunch.

The good news is that analysis of rock cuttings is indicating we are not far from the fault. We know this from fragments of mylonite, which is a rock formed at temperatures of more than 300°C by the smearing out and recrystallization of quartz grains.

In the meantime, geophysical logging of the borehole (see last blog) and analysis of data is producing interesting results. 

The borehole is J-shaped, with the bottom deviated 40° from vertical (animated figure). This places the bottom of the hole below the Whataroa River about 200 m northwest of the drill rig. This is exactly what we had hoped would happen: the deviation is taking us directly towards the fault. The onset of mylonite rocks is right in line with predictions that we should be getting close.

Borehole geometry to 825 m.  R. Sutherland

We have been able to make a very detailed analysis of the inside surface of the borehole (example shown in animated figure). We have discovered that the layers in the rock consistently dip southeast at about 60°. This is a little steeper than predicted and a slight concern, as it could mean that the fault is deeper than predicted. The mylonite cuttings are giving us a clue that we are close, but we will soon find out where the fault is.

Borehole surface over a 1.5 m interval.  J. Townend

Funded by: the International Continental Scientific Drilling Program (ICDP); the Royal Society of New Zealand Marsden Fund; GNS Science; Victoria University of Wellington; University of Otago; and governments of NZ (MBIE), UK (NERC), & USA (NSF).

DFDP-2 @ 828 m, wireline logging, schools and locals

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

A lovely morning with drilling progressing smoothly.  2/12/14.  Photo R. Sutherland.

We made solid progress over the last week. Our plan was to stop and set steel casing at 800 m depth, but we always knew that a detailed analysis of rock cuttings would be needed to confirm the depth of the fault. We reached 828 m depth after dinner yesterday.

The cuttings geology team is telling us that we should drill a bit deeper before we cement casing into the borehole, but we took a break from drilling last night for several reasons:
(1) drilling equipment needs to be checked and maintained;
(2) we wanted to survey the orientation and state of the borehole; and
(3) geophysical measurements made deep in the borehole today will inform our decision about what to do next.

Geophysical instruments (sondes) are lowered into the borehole on a wire rope from a special winch that precisely measures depth. Cables inside the wire transmit data to a computer at the surface. This process is called ‘wireline logging’.

Wireline logging sonde.  Photo J. Thomson

There are many different types of sonde. Today we will be measuring: electrical conductivity and temperature of the mud in the hole; seismic wave-speeds and electrical conductivity of the rock; natural rock radioactivity; borehole orientation; borehole shape; and images of the borehole wall that reveal rock fabrics and fractures.

This video gives a bit of an explanation of some of the wireline logging tools we use:


We have had several open days recently with lots of locals and two schools coming to visit.

Carolyn Boulton explains rock cutting and crushing to Hokitika High students. 4/12/14 Photo J. Townend

Jennifer Eccles explains earthquake sensors to Hokitika High students in the rain. 4/12/14 Photo J. Townend

DFDP-2 is funded by: the International Continental Scientific Drilling Program (ICDP); the Royal Society of New Zealand Marsden Fund; GNS Science; Victoria University of Wellington; University of Otago; NZ Government (MBIE); UK Government (NERC).

DFDP-2 @ 760 m, rock cuttings team

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

Naoki Kato (Japan) cleans rock cuttings, Mike Allen (UK) makes microscope thin-section slides, Carolyn Boulton (UK) analyses dried rock cuttings under a microscope, and Tim Little (NZ) records analysis. 28/11/14.  Photo J. Townend.

The sun is out and drilling is going smoothly. We passed 760 m before lunch. The drillers are happy.

Tony Kingan, Head Driller, looking happy with progress. Photo R. Sutherland

The rock cuttings team tell us what the rock is that we are drilling through, and how far we are from the fault. We’re getting closer, but we are not quite there yet. The plan is to start coring 100 m from the fault or at a depth of 1000 m, whichever comes first.

The rock cuttings team collects, cleans, dries, sorts, describes, counts, glues, and grinds the cuttings, analyses them under a microscope and then enters the data into a computer. Everyone has had to work hard in shifts over the last few days to keep up with drilling, but it is more interesting than waiting for equipment problems to get solved. This video shows what's involved:


Many of the team have now been here for more than two months — and some of us have been here most of the time since August! It is becoming clear that we will be here well into January, but only after a brief and well-earned Christmas break.

Rewi Newnham (left) talks to Rupert Sutherland about the DFDP-2 drilling project.  Photo J. Townend.

Lisa Craw and Alan Cooper are given a site induction by Alex Pyne.  Photo J. Townend.

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.

DFDP-2 @ 635 m, packer tool

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

Doug Schmitt, Dierdre Mallyon, and Alex Pyne take a moment from packer tool testing. 28/11/14. Photo B. Celerier. 

Drilling has been going smoothly over the last few days. We reached 635 m depth at breakfast time. 

We will continue this phase of drilling until the team analysing rock cuttings tell us we are near the fault. Then, we will put steel casing (pipe) into the hole and cement the annulus (gap between rock and steel), to secure a foundation for deeper operations.

In the meantime, we are also mobilising and testing tools for the next phase. A new tool for imaging the borehole wall at high temperatures arrived this morning from Europe, and a packer tool was tested on site.

Water circulating through packer tool. Photo B. Celerier.

A packer is a rubber element that inflates to seal and isolate a section of the borehole. It is then possible to pump water down the pipe that is inside the packer and inject water into the isolated section of rock. The process works in reverse too: you can produce a small amount of fluid out of the rock from an isolated section of borehole.

Why do we want to do packer experiments? 

(1) To determine how easily fluid can move through the rock; and 

(2) to collect fluid for analysis. 

When combined with other data, we can also use this tool to evaluate the stress state of the rock, which is interesting for us earthquake scientists.

Checking the packer tool works OK. Photo B. Celerier.

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.

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.

DFDP-2 @ 520 m, geothermal resource?

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

Happy to be drilling again. Onsite shift scientists under some of our flags.16/11/14. Photo R. Sutherland.

What a great team we have at the DFDP project. About 120 scientists from 12 countries are involved in DFDP-2, and more than half of them have been working with us here onsite already.

We started in August and won’t be finished until Christmas. It’s a long time away from families and friends, but the team here has great morale. It will take at least a year to make systematic lab analyses of samples, and then another two years to do specialised analyses. It really is a big job.

We are making steady progress and passed 520 m at breakfast today (17 Nov.). We are drilling a 212 mm diameter hole on our way towards the fault, sampling and analysing rock cuttings as we go.

Geothermal conditions in the borehole have turned out to be one of the most popular talking points amongst scientists and locals. We have made 9 temperature logs of the borehole. When not cooled by circulating fluids, the borehole is at about 85°C at 500 m depth. This is about 70°C hotter than at the surface. For an average location in New Zealand, or on most other continents, the temperature increase would be about 12°C. The geothermal gradient – the rate of temperature increase with depth – is six times normal. The hot conditions underground are of scientific interest, but are also a challenge for sensitive instruments.

Is there a commercial geothermal resource here?

Our main focus is earthquake science, but there is a reasonable possibility that we have discovered a significant resource in the process.

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.

DFDP-2 Calamity resolved! Mostly.

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

A lovely morning at the site. 13/11/14. Photo R. Sutherland.

Successful fisherman, Richard. 
Photo: R. Sutherland 13/11/14

Yesterday, after it was clear that the drill had snapped and been left at the bottom of the hole (489 m depth), the drillers flew into action, quite literally. They went up to New Plymouth in their plane, obtained a fishing tool, got it back to our site, deployed it, attached to the lost drill, pulled it back to the surface, and took it apart. This was all complete by 4 a.m! It was an impressive effort.

The drill bit was damaged, but still in one piece. The bearings were broken. It was also badly worn, so must have been cutting a hole that was at least one cm too narrow. We think this explains the damage to the bottom stabiliser, but are still piecing together the facts.

Our next challenge is to check the integrity of all components and obtain new stabilisers. We hope to be drilling again very soon.

Everyone on site is now familiar with what a bottom-hole assembly (BHA) looks like. If you want to watch an explanation of the various parts and what they do, see our youtube video:


https://www.youtube.com/watch?v=A6gLpzR8mlI

Comparison of broken drill bits. The bit recovered today (left) is badly worn and the bearings are loose. The bit dropped previously (right) has broken teeth and has cones jammed together. Photo R. Sutherland. 13/11/14.

Broken pin with stripped thread. This is the top of the recovered piece of BHA. Scratches visible at the top of the photo are from the fishing operation. 
Photo R. Sutherland 13/11/14.

Driller, Paul, is standing next to the fishing tool and a part of the recovered bottom section of the BHA. The drill collars beneath are part of the upper BHA. 
Photo R. Sutherland 13/11/14.

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.