Helicopter rendevous

RAB tool deployment

Blown Pipe

Free fall
Funnel

At Sea Report from the Bismarck Sea:
It was quite a week

As you may recall, in my last report I said that after loosing 200 m of drill pipe in the Snow Cap site (Hole 1188A) we were moving to a place called Roman Ruins. Well, here is what has happened since then.

We lowered the camera and when the seafloor appeared before our eyes, we were treated with a set of chimneys and structures that were quite different from the overall topography of our first site. After a couple of hours of surveying, a spot was chosen and drilling operations began in Hole 1189A. Core recovery was low but drilling went along fairly smoothly for a while. We made several temperature measurements along the way by lowering thermometers that record a maximum temperature on the core barrel that houses the core that is being cut by the drill bit. Temperatures ranged between 35 to 39º C, which is in the range of a hot summer day ranging from 95 to 101º. These temperature measurements proved to be important because not only they were cooler than what we were expecting but also when we reached 125 mbsf, King Neptune decided to claim another victim as the drill string got stuck and we were unable get free. There were concerns that if the temperatures were too high and we had to use explosives again, they could detonate before they were set in place. The low temperatures eased all concerns and it was time to wake up Kerry Swain (Schlumberger Wireline Engineer) so he could begin the process of assembling explosives to blow the pipe free. He was woken up during his prime sleeping hours. Once he had all the equipment ready, with one swift "KABOOM!", we were free. The final tally for Hole 1189A at the Roman Ruins site is the following:

Latitude: 3° 43.2'S
Longitude: 151° 40.5'E
Water Depth (m): 1690.2
Number of Cores: 13
Interval Cored (m): 125.8
Core Recovered (m): 8.58
Percent Core Recovery: 6.8

Now, it was time to go somewhere else. We chose to go to an area called the reference site where it was thought the location would be least affected by high temperatures and would produce a good representation of the stratigraphic sequences and the fluid flow patterns in the area. We lowered the camera once again and after finding a suitable place we officially began drilling operations in Site 1190. Drilling difficulties appeared almost immediately in Hole 1190A as we got stuck at 6 mbsf, but luckily we were able to get free. We tried a few more time in Holes 1190B and 1190C until we decided not to risk loosing any more drill pipe and once again move to our first site (Snow Cap) where even though we lost pipe, we were also able to reach more than 200 mbsf. The final tally for Site 1190 (Reference Site) was not too good as shown below:

Hole 1190A Hole 1190B Hole 1190C
Latitude: 3° 43.3'S Latitude: 3° 43.3'S Latitude: 3° 43.6'S
Longitude: 151° 40.6'E Longitude: 151° 40.6'E Longitude: 151° 40.6'E
Water Depth (m): 1703.1 Water Depth (m): 1701.1 Water Depth (m): 1696.1
Number of Cores: 1 Number of Cores: 1 Number of Cores: 3
Interval Cored (m): 9.1 Interval Cored (m): 8.6 Interval Cored (m): 17.2
Core Recovered (m): 0.03 Core Recovered (m): 0.25 Core Recovered (m): 0.40
Percent Core Recovery: 0.3 Percent Core Recovery: 2.9 Percent Core Recovery: 2.3

The decision to go back to the first site had a direct impact on the logging group, which, in addition to me, includes Anne Bartetzko (Logging Scientist from Aachen, Germany), Anthony Strahan (Anadrill Engineer from Australia), and Kerry Swain (Schlumberger Wireline Engineer from Texas). A decision was made to attempt to drill a hole to 75 mbsf with a logging-while-drilling (LWD) tool called Resistivity-at-Bit (RAB) and deepening the hole with a newly designed bit called the Advanced Diamond Core Barrel (ADCB). The decision to drill with the RAB was exciting and scary at the same time. It was exciting because I have been one of the proponents for using this tool in ODP but it was scary because we have been getting stuck in almost every single hole and I was not looking forward to the possibility of loosing this expensive tool. It was time for us to earn our keep.

However, before we could deploy the RAB, we had to wait for the arrival of a helicopter that was bringing a set of lithium batteries for the tool. We had left Guam without these batteries because they were still in Japan after being shipped from Australia. We could not get a confirmation of their arrival so we left without them and made arrangements for a shipment to Rabaul (New Britain) and a helicopter transfer to the ship. Once the batteries arrived at 8 AM (local time), we were ready to begin drilling with the RAB, a first in ODP history.

Drilling went pretty fast for the first 15 m and then we encountered our first set of difficulties as we stalled the top drive and we had 100,000 lbs of over pull (resistance when an attempt to retract the drill string is made). This was tense situation because of our recent drilling history in this area but after working the drill string for about 10-15 minutes, we became free and continued operations. The entire time that drilling operations continued was nerve wrecking because we continued to encounter difficulties followed by periods of relatively easy drilling. Finally, after averaging 9.5 m in 55 minutes we spent the last 2 hours drilling 4 m. A decision was made to stop drilling operations at 72 mbsf because we were close enough to our original target (75 mbsf) and re-enter the hole with the ADCB bit. I was relieved because the tool was coming back and we did not loose it. After 26 hrs of monitoring the situation, I could go to sleep now.

The hole was re-entered with the ADCB after dropping a free fall funnel (big funnel that comes in two pieces that are welded around the drill string and then dropped to the seafloor to facilitate re-entering a hole and resume drilling operations). We got the RAB back onboard, a little bit battle tested, but in one piece. Now it is time to download the data and begin our processing and interpretation. Colin Bremner (Driller), Phil Christie (Driller), and Pepe Esteves (Senior Tool Pusher) deserve most of the credit for bringing the RAB back onboard because the did most of the hard work of getting through all the tough spots.

So you may ask, why are we having so many difficulties? There are different theories but in the past, these active environments have been extremely difficult to drill because of the nature of the rocks that are usually encountered. So far we have found large amounts of a sulfate mineral called anhydrite (CaSO4) which seems to comprise a large amount of the matrix of the rocks within this area. Anhydrite is stable at temperatures ranging from 150 to 200º C and the problem begins with the drilling process that circulates cold water form the ship into the formation. This cold water tends to dissolve the anhydrite and as the formation becomes unstable and begins to crumble, large pieces start filling the hole and trapping the drill string to the point that we are unable to retreat or rotate. The volcanic rock also proves to be a challenge because their glassy texture shatters during the drilling process creating a similar unstable situation of the borehole walls. The bottom line is, this is not easy at all.

In the wildlife report, I have seen schools of squid, sometimes in the hundreds, congregating around the ship at night. They tend to feed on smaller fish and the bigger fish tend to feed on them. The water in the vicinity of the ship becomes very active at night. There is also tuna and mahi mahi (also know as dolphin fish or dorado). A very peculiar kind of fish has also been swimming around. It has elongated grayish body and very peculiar white lips. I have not figured out what kind of fish this is but I will continue to try to find out.

Today, we had a stormy morning and I could not see land. The seas are still fairly calm but as the storms were rolling in and the rain began to fall, I could not see the sunrise. I have become accustomed to watch the sun come over the horizon in the middle of my shift around 5:30 AM. It is the best time of the day because everything is still quiet and the temperatures are still bearable. The same cannot be said by 8:00 AM when it is already plenty warm and humid. However, today was a beautiful day in its own kind of stormy way. One of things that I like about being at sea is that I become more in tune with nature and learn how to appreciate the little things like a sunrise, all over again.

Once again, it is time for me to go so until next week.