892 m: Premature end to DFDP-2B

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

A core of cement and borehole wallrock from 471 m depth. 15/12/14. R. Sutherland.

Yesterday afternoon, we decided that it was not sensible to continue drilling in the DFDP-2B borehole. We will not drill in January 2015. The broken PWT steel casing is severely misaligned and cannot be repaired. We will securely cement it in place, and then use the well as a geophysical observatory – though with less capability than planned, and above the fault.

It would be possible to continue drilling from 463 m in the DFDP-2B hole, but only with a 4.5” (114 mm) bit, or smaller. A range of technical and safety concerns make it very unlikely this is a feasible way to achieve our goals below 1000 m depth.

Our primary concern now is to ensure that the final cementing operation is done well. This is scheduled for later today (Wednesday 17/12/14). After Christmas, we will drill out the excess cement to leave a sealed borehole to a depth of 400 m. We will install a wellhead, a seismometer, and then make temperature measurements.

This is not the end of the DFDP-2 project. We did not achieve our goals of making observations and installing instruments within and below the fault zone in DFDP-2B; but we obtained important data and samples to a depth of 893 m. These show that the Whataroa Valley is even more interesting than first thought, and that our original plan was feasible.

This project is interesting to the international science community, because we are investigating a fault that is due to fail in a large earthquake, and because we can investigate it deep enough to account for the complications of mountainous terrain above. This has not been done before.

We have learnt that the Whataroa Valley is much hotter than anticipated. The base of our planned borehole at 1300 m has a temperature of about 190°C. Temperature is fundamental in rock mechanics, and 190°C puts us in the lower half of the brittle crust, where some very important earthquake processes occur. Sampling any fault in this state would be an important world first. It is high risk, but with potential for very high reward.

More blog posts will follow…

Virginia Toy walks past a table of concrete. It was not what we had hoped for.
14/12/14. R. Sutherland

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).

Calamity 3, broken casing

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

HWT (4.5”, 114 mm) steel casing. 13/12/14. R. Sutherland.

Nobody likes a sequel, and a sequel to a sequel is even worse. Yes, we dropped another heavy steel tube to the bottom of our borehole. This time it was worse, because our recipe had 40 tons of cement added to the 25 tons of steel in the hole.

It was a complicated casing operation last Wednesday, and it was done carefully. We lowered PWT casing (5.5”, 140 mm) with only a minor hitch – the float shoe apparently failed with a third of the pipes still on the rack. Before this, mud had been displaced from the borehole as each piece was added. A float shoe is a one-way valve at the bottom of the pipe that stops mud entering, giving the pipe some buoyancy (air inside it) and reducing its effective weight, and preventing backflow when the pipe is cemented.

Float shoe for PWT casing. 10/12/14. R. Sutherland

Next, a BQ steel pipe (2.25”, 56 mm) had to be threaded 890 m to the bottom of the borehole (8.5”, 210 mm diameter), running alongside the PWT casing (5.5”, 140 mm). Simple maths tells you that a 14 mm tolerance over 890 m of rubbing against jagged rocks had a small chance of success. But it went in!

Next, a stainless-steel tube with delicate optical fibres inside was threaded into the BQ pipe. That worked, and we tested our sensors. OK too!

At 4 a.m. on Thursday, it seemed that everything had gone as planned. Just in time too, because the trucks showed up at 5 a.m. to set it all in concrete.

Concrete appears at wellhead. PWT and BQ pipes visible, and fibre optic cable held by clamp. 

11/12/14. R. Sutherland

By 9 a.m., the joyous mood had changed. Cement appeared back at the surface much earlier than it should have, and pump pressures were lower than predicted. We quickly deduced that the PWT steel casing had broken.

Our immediate action was to flush cement out as best we could before it set. Fortunately, we had waste pits prepared for just such an emergency.

Cement pumped from the hole. 11/12/14. R. Sutherland

The next step was to determine where the break in casing had occurred, and what we could do about it. Over the last few days we have been trying to determine the state of the borehole 430-470 m below us.

We have analysed records of pump volumes and pressures, and digital data from the drill rig computer. This shows that a significant event occurred at 11:42 a.m. on Wednesday, and it seems this is when the casing broke apart. The depth to the broken joint is estimated to be 436 m.

The drillers made up an HWT drill-string (4.5”, 114 mm) that fits snugly inside PWT pipes, and carefully lowered this into the borehole with a core barrel and bit. We touched an object at 436.0 m, pushed it to 437.0 m, and then cored it. It was the cementing plug. This was the last thing pumped after the cement. It floats, so its position seems consistent with our depth estimate for the break.

We advanced farther and eventually started coring rock below 470 m. This is bad news. It means that the pipes are not aligned.

Cement plug and concrete core. 13/12/14. R. Sutherland.

It is still too early to tell exactly what this means for the project. Several options are available to us. Our top priority is to remediate the immediate situation and secure the upper casing. However, we need to think through all possibilities before putting more cement in the borehole.

Everyone is looking forward to a break over Christmas. It has been physically and mentally very demanding for the last 16 weeks, and it still seems like there is so much more to do.

The latest addition to our team is as big as Virginia but not as ferocious.

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).

892 m, decision time, steel casing

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

The view downstream. It is 600 m to the bridge. 4/12/14.  Photo J. Townend.

We reached a very important decision point today. At 8 a.m. this morning at 892 m depth, we decided to stop drilling and to cement casing into the hole. A bunch of things now have to happen so that we are ready to start the collection of rock core.

We first have to clear the borehole of rock chips and cool it by circulating mud. The mud emerges at 52°C. How hot would it be if we weren’t drilling? We will know in the next week or so.

Before we cement PWT steel casing (5.5 inch = 140 mm diameter pipe) into the hole, we will use wireline tools to log the hole. This is our last look at the borehole wall before steel and cement get in the way. Logging will start about midnight tonight.

New PWT casing is ready to go. Photo J. Townend.

The process of putting casing in the hole is fairly complicated. It has to get down and around the J-bend in one piece. The bottom of the hole is now 250 m horizontally towards the road bridge and away from the drill site (see our last blog). Next, we have to run another smaller steel pipe next to it – this is going to be a tight fit. Then, we have to insert a fibre optic cable down the second pipe. Finally, we have to pump 25 cubic metres of cement down the inside and back up the outside of the casing without it leaking into the rock or setting hard before we are finished.

If all that happens without a hitch, then we will be hoping to collect our first core this weekend.

View from the geologists’ cage.  J. Townend.

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.

DFDP-2 @ 489 m: Calamity! Again!

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

Fresh snow in Whataroa. Drill site is up the valley on right of photo.
12/11/14. Photo R. Sutherland.

Misfortune struck in the early hours of Wednesday morning. Drilling progress had slowed the previous day, and then it totally stopped. We had reached 489.5 m depth.

The drill was removed from the hole and we got a surprise: the drill bit was missing. So was the bottom 7.5 m of the bottom-hole-assembly (BHA).

Steps to recover the lost BHA piece are in motion. We know how to fish it out from our last experience.

Crossover (left) with stripped thread and a broken fragment inside.
It should look like the male thread on the right.
Note the stabiliser just above it.
12/11/14. Photo R. Sutherland.

Worn stabiliser. 12/11/14. Photo R. Sutherland.

Close-up of stripped thread and broken fragment still engaged.
12/11/14 Photo R. Sutherland

 The loss was caused by equipment failure: a broken thread. It is the same section of drill collar that bore the full impact when the BHA was previously dropped to the bottom of the hole, so it may have had a weakened thread. However, there are also signs that drill bit failure contributed to this incident.

The science team noted anomalies in the hours before the incident. Steel shavings were collected (damage to stabiliser and bit?) and traces of hydrocarbons detected (grease from the threads?). The bottom stabiliser is badly worn at its base, suggesting the hole was not in gauge (it was too narrow). It seems that the drill bit may have started to fail at least 8 m before BHA separation occurred.

Wireline logging is underway. It will help us understand the state of the hole and what happened.

We hope to be drilling again in a few days.

These little fellas really didn't care about our woes. They are always happy to see us.
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.

DFDP-2 @ 430 m: Drilling hole again

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

It certainly took longer to get drilling again than we had hoped, but we are now making steady progress. We started drilling again at 7 pm last night and passed 430 m depth this morning.

The delay was caused by annoying fragments of metal that were still in the borehole after we had recovered the main BHA.

Fishing tool with a strong magnet inside it covered in fine metal shavings 9/11/14.
Photo: R. Sutherland.

The most elusive object was a weight that normally resides at the bottom of the winch rope (just below the flag, see photo of the new one). It was eventually retrieved using a strong magnet in a steel pipe (see photos).

Fishing tool with our last catch. 9/11/14. Photo: R. Sutherland.

The BHA and a nice new tricone drill bit were installed yesterday and we are now making good progress. The science team and drillers are very pleased to have put the dropped BHA drama behind them.

Flying the flag again 10/11/14. 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.

Happy drillers

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

Broken drill bit recovered from the lost BHA. 5/11/2014 Photo R. Sutherland.

Happy drillers: Luke Valour (left) and Tony Lyons (right). 5/11/14 Photo: R. Sutherland.

Was it great to see that smashed up drill bit finally recovered? Yes it was!

It took longer than we thought to get everything on deck, but finally the fish was landed, cleaned, and checked. The drill bit was a write-off (see photos), but the other components were surveyed by an engineer (who arrived by helicopter) and they are apparently undamaged — they are very solid steel.

Minor fishing operations continue as we recover remaining small fragments, but we are nearly there. We will collect wireline logs tonight. Tomorrow, a new drill bit will arrive, and a new BHA configured. We have an engineer’s report into the original winch failure and repairs will be complete tomorrow.



Hail on us, sunshine everywhere else. 4/11/14 Photo: K. Sauer

Check out our new video... Minerals and Alpine Fault drilling

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.

Landing the fish

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

Photo: R. Marx.

The BHA — 7400 kg of steel — was lost to the bottom of the hole over a week ago. The weather packed up shortly afterwards. It was a pretty grim week to be a scientist or a driller in Whataroa. But, the science and weather forecasts are good.



Photo: R. Marx.

The drillers have been fantastic. They methodically and calmly worked at the problem, systematically cleaning out loose materials and deconstructing the top of the lost BHA. It is amazing how they can picture and even feel what is going on 324 m underground. Over the last 10 days they have recovered wire rope, a shackle, a piece of wet rag, the top and then the bottom of the heavy steel hauling plug. They grabbed stuff with all sorts of special tools and even lifted the whole assembly by 5 m at one point. The mood has steadily improved.

This morning, just as the hail set in, they successfully latched onto the top of the BHA. By lunch time, the top of the ‘fish’ was visible at the surface. Tomorrow morning it will be landed. Then there will just be some minor bits of trash to clean up. Hopefully we will be drilling again by Thursday.



Drillers landing the fish. Photo: R. Marx.

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 @ 396 m: Calamity! Dropped bottom-hole-assembly (BHA)

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

Drill site 22/10/2014  Photo J. Thomson

We removed the drill from the hole last Thursday (23/10/2014) at a depth of 396 m, so that we could survey the hole and reconfigure the drill. The wireline logging survey went smoothly. It is about 56 degrees Celsius near the bottom of the hole.

Wireline logging tool. Photo: J. Thomson.

The drill bit was found to be worn and the hole had reached 12° off vertical. The deviation was caused by mechanical interaction between the drill and the dipping rock fabric. At least it was heading in the right direction (northwest, towards the fault).

Worn PDC drill bit. Photo: R. Sutherland

 Tricone bit, collars, and stabilisers. 

24/10/2014 Photo: R. Sutherland.

The drilling team reconfigured the drill pipe and switched to a new drill bit. This time we used a tri-cone type of bit. The bit is attached to heavy, rigid ‘collars’, and wider pieces of pipe called ‘stabilisers’ that centralize them in the hole. The entire ‘bottom-hole assembly’ (BHA) weighs 7400 kg in mud and is 72 m long. It is connected to the surface with steel drill pipes.

Fishing tool and fragment of
recovered wire rope. 27/10/2014
Photo: R. Sutherland.

Calamity struck at 13:09 last Friday afternoon (24/10/2014), just before the Labour Day long weekend. A wire rope snapped and the entire BHA dropped down the hole. We are very relieved that nobody was hurt. An independent technical investigation is being conducted by an engineer and we await his findings.



Our immediate strategy is to try and retrieve the BHA from the hole. This process is known as ‘fishing’. The BHA weighs 7.4 tons, so the first step in fishing is to extricate anything preventing a good grip. The drillers were successful in fishing out of the hole some broken fragments of wire rope and some of the top fixings. They are now working to establish whether they can lower a socket over the top of the BHA. If that is possible, they will use a special tool used in the oil drilling world to lock onto the BHA and lift it back to the surface. This tool is being transported from New Plymouth.

Fishing tool 30/10/2014  
Photo: J. Townend.

What does this mean for the project? It is certainly going to delay progress, but everyone is working hard to recover and continue. While fishing operations are underway, we have been analysing the data collected so far and documenting our preliminary findings.

If the BHA cannot be retrieved, we will cement it in place and side-track (deviate) the hole above it. This will mean re-drilling about 100 m of hole, but we can re-use most of the steel casing already installed.
We had expected delays of some sort from the outset, so we have contingency built into our scheduling. The delays so far mean that the project will continue into December, and we are very much hoping to get back on track so that we can finish before Christmas.

Nobody said it would be easy!



Check out our new video that shows you what a bottom-hole-assembly actually looks like before it is assembled and put in the hole...

Check out our video that describes the purpose of the DFDP project...

Some comedians did a parody of the safety of our project last week, but is it safe? We think it is, but don't take our word for it. See the video made by the Chairman of our independent Safety Panel...

See also:
The DFDP-2 wiki pages


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.