"Looks Like We Made It"

16 July 2005

Assembling the drill string.

Subsea camera and beacon being lowered.

We arrived on site at 1045. Our coordinates are 6° 44"N, 91° 56"W, with nothing around as far as the eye can see…and my students in Romulus, NY think they’re in the middle of nowhere!

Once we were in position and the thrusters were lowered, the drill string was assembled and run into the hole to just above seafloor. Then a beacon (a positioning device that sends up an acoustic signal to receivers on the ship) was attached to the subsea camera and deployed to the seafloor. Amazingly, when the camera reached the bottom, we found ourselves right on target. What a feat of navigation! At approximately 2045 re-entry was accomplished. The only thing I can compare it to would be the moon landing in 1969. To my surprise, there were squid and fish swimming around the lights and camera – over 3400 meters below the surface!

17 July 2005

View forward from the logging winch

The water sampling tool (WSTP) was sent down the drill pipe on the wireline to obtain a water sample and measure the temperature in the hole. After it was brought back to the surface, the first of two logging tools were assembled and lowered. Logging begins once the drill string re-enters the hole and continues as the logging tool is raised. The logging tool strings contain a series of instruments that measure and send back a constant stream of data on hole diameter, temperature, resistivity and conductivity of the rock, as well as making a 360° “image” of the hole. All of the information, including depth, is monitored from the logging van located aft of the pipe racker.

The logging winch holds the logging cable that stretches forward to the drill floor, up into the derrick, then down through the drill floor into the drill pipe.

18 July 2005

Observing the Magnaflux   process under cover of black canvas.

Box threads on a joint ready to be Magnafluxed.

Measuring the core barrels.

A used (left) and new (right) roller cone bit used for rotary coring in hard formations. *

Today the logging process was completed and the tool was removed. All went well. The logging scientists tell us that Hole 1256D is in excellent shape! We will log the hole again when we finish the drilling at the end of the expedition.

As the drill string was retrieved, the connections in the drill collars (the large diameter pipe that make up the bottom-hole assembly, or “BHA”) had to be “Magnafluxed” to check for cracks. During Magnafluxing, the joint threads are cleaned and sprayed with fluorescent magnetic particles that, when exposed to a strong magnetic field, will identify surface and sub-surface cracks. When viewed under ultraviolet light, the cracks glow bright green. This tells Joe “Bubba” Attryde, Core Technician (USA), that there is a cracked tool joint that needs to be taken out of service.

I was invited to the rig floor to watch the roller cone drill bit (used for hard formation coring) being changed and to observe two core barrels being measured (they have to be exactly the same length) and readied to accept core. The degree of precision required is incredible. As large and unwieldy as the equipment is, you wouldn’t think that the tolerances would be so small. Just like before, the ship’s dynamic positioning crew re-entered the hole successfully. These guys make it look so easy!

When coring starts, a plastic core liner is put in the core barrel before it’s dropped. The core barrel freefalls from the surface to the depth of the bit. During drilling the bit grinds away a ring of rock leaving a column in the middle – the core. The core slides through a mechanism with spring hinges called a core catcher and into the core liner. A special tool called an overshot is lowered to retrieve the core barrel when drilling reaches the required depth. 

19 July 2005

Coring begins!

Removing the core catcher and core. *

Cutting and capping the very first core. *

Marking the core for splitting into archive and working halves. *

Cutting the core pieces in half.

Me at the labeling table!

As the Teacher At Sea, one of my goals is to follow the route of a core as it makes its way through the lab on the way to being imaged, subjected to sound waves, soaked in seawater, sawed, labeled, epoxied, slivered, observed under a microscope, ground to a powder, chemically analyzed, acidified, X-rayed, described, weighed and measured. The first stop on my journey is the core receiving platform, the catwalk.

The first core barrel went down at about 0600. The initial core was expected by 1200 but the core arrived sooner than expected; at 0945, the “core on deck” announcement came across the ship’s intercom. This brought everyone rushing to the catwalk. When the first core was laid out it was like a Hollywood premier, with cameras flashing and lots of on-lookers!

Once laid out, the core is measured and cut into 1.5m sections for ease of handling. The core liner is capped on both ends. A blue end cap is used at the top of the section and a clear one is put on the bottom. The capped section is then taken to the splitting room in the core lab. 

In the splitting room the core liner is split into what will become the working and archive halves of the core. With the help of an igneous or metamorphic petrologist or a structural geologist (or all three) the broken rock pieces that have connecting planar features or veins are aligned from piece to piece and fitted together. Non-matching pieces are separated into bins with plastic dividers.

Once divided, the whole round core goes through the physical properties lab and the whole round imaging system, otherwise known as the “DMT.” (More on them later – I will report on each lab separately!) Once through those two labs, the core pieces are then cut by hand on a rock saw into archive and working halves.

Sawing through the rock is relatively simple if you have the right tools. Armed with safety glasses and ear protection, I was given a chance to cut the rock. Some of the pieces cut “like butter.” It was a bit intimidating to put my fingers next to a saw blade but after the first time, it wasn’t so bad. The rock saw blade is diamond tipped and won’t cut fingers the way it cuts through a rock.  (REALLY!)

The two halves are taken from the splitting room to the main part of the core lab, where each piece is labeled. My day was spent helping on the catwalk, in the splitting room and at the labeling table.

Each tiny label is glued with epoxy to keep it in place. By the time the epoxy dries, an average of two hours has elapsed since arriving on deck. One of the lab activities for my final Teacher At Sea project focuses on the curation process performed at the labeling table. (Labeling is not the easiest or most exciting job I’ve ever done – it can be tedious and it’s easy to make mistakes.)

One of the most important steps in making sure a core is properly curated is the digital imaging of all the archive halves with the Digital Imaging System (DIS). This image is placed on the Visual Core Description (VCD) sheets by Debbie Partain, Ship’s Yeoperson (USA) for later use by the igneous, structural and alteration science teams.

After imaging, the archive half of the core travels to the description table. Every detail is described and catalogued on the Visual Core Description sheet. Each VCD sheet contains a photo of the core, a series of graphic description symbols and a place for a written description. Not only do the descriptions help to determine the samples taken and the tests to be done, when compiled they will provide the science party with the overall picture of the geologic story at this superfast spreading center.

20 July 2005

Discussion at the sample meeting.

Cutting a sample.

We have processed four more cores, bringing the total number of cores to eight, so the newness is starting to wear off.  There are fewer and fewer people showing up on the catwalk when “core on deck” is announced. Everyone is busy in their labs.

The first sample meeting was held. The scientists hear an overview of the daily findings and then discuss which samples should be taken from where for the on-board testing. When possible, they collaborate on sample usage so there will be minimal destruction to the working half of the core.

Once the decisions has been made, the core is marked so that the technicians can cut the sample material from the core. It is a precise and laborious task requiring great concentration.

21 July 2005

“Core on deck” at 0555! I’m not quite awake, but the core keeps coming.

Cutting on the SuperSaw.

Me getting to drop the core barrel.

We continued to process core through the core lab, and I was given my first chance to cut core on the custom-made IODP SuperSaw. The SuperSaw is a rock saw that moves along a stationary track. The core sits in a V-shaped groove and the saw is pulled over it. This saw is used for long intact pieces of core that are too long to cut on the regular rock saw, where you push the rock by hand.

Between core recoveries today, there was time to keep the paperwork flowing. I had a chance to do some clean-up work on my journal and get a couple of minor projects completed in the lab.

In the afternoon, I was able to “drop” the next core barrel. To “drop” a core barrel means to release it so that it goes from the surface down to the bit – in this case, about 4400m. The core barrel is placed in the top of the drill pipe, where it hangs on a stop (a piece of steel with a handle) while all of the lifting equipment is removed. When clear, the stop is pulled out and the core drops quickly, beginning its descent to the bit. The core barrel free-falls from the surface, but it’s much slower than one might expect. After about 12m the drill pipe is filled with water, which slows down the core barrel and prevents it from slamming into the bit.

Once the core barrel is down, it latches into place on a bearing and doesn’t rotate with the bit. This helps keep the core from breaking. It’s awesome that over the years engineers and drilling personnel were able to develop a system like this!

22 July 2005

During the night there was very good core recovery: 9.6m drilled, 7.1m recovered. There are six sections to this core. It is almost all “whole round,” meaning there are very few small pieces that rolled around and were ground up in the core barrel. There are a lot of long pieces so most will be cut on the SuperSaw.

We’ve recovered 11 cores, and now the bit needs replacing. The bits are only good for about 50 hours of drilling. During the replacement process all of the pipe will be brought to the surface and a new bit installed. Then the process reverses and pipe is added and lowered.

After the bit is replaced, the hole will be re-entered for the third time. The pipe trip process takes about 20 hours, so everyone has a chance to catch up before the next core will be brought up.

* Photo by Shannon Housley, Imaging Specialist, IODP/TAMU (USA)