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IODP Expedition 335:
Superfast Spreading Rate Crust 4
Week 2 Report (18-24 April 2011)
PDF file is available for download.
The 478 nmi voyage to Hole 1256D was accomplished at an
average speed of 10.6 knots. The vessel was positioned on the established
coordinates of the hole at 0115 hr on 19 April. The water depth established on Leg 206 is 3645.4 mbrf. The final depth of the hole at the end of Expedition 312,
when this hole was last visited in December 2005, was 1507.1 mbsf.
Hole 1256D was reentered with a hard formation Smith 9 7/8"
F9 tricone bit affixed to an mechanical bit release (MBR) and 4-stand bottom
hole assembly (BHA). The initial objective was to test the openness of the hole
to a depth of 1100 mbsf without circulation or rotation so that, if clear, an
equilibrium temperature profile could be run to 1350 mbsf using the MTT logging
suite. This would be followed by a borehole water/microbiology sampling run
using the WSTP.
The drill string was lowered to a depth of ~920 mbsf where
it encountered a ledge precluding the planned wireline operations. This
interval had impeded smooth transit of the drill string on initial re-entry
during Expedition 312. The wireline caliper, FMS and UBI logs from that
expedition indicate an eroded zone from ~920 to 935 mbsf. Starting at 2330 hr on 19 April and for
32 hours until 0600 hr on 21 April the driller attempted to work past the
obstruction without success, and the drill string was recovered. A more
aggressive Reed 9 7/8" tricone bit (IADC Type 517), usually employed in softer
formations, was mounted along with a tandem set of junk subs and Hole 1256D was
reentered for the second time at 0105 hr on 22 April. Drilling on the bridge
resumed at 0445 hr and continued to 2100 hr (16.3 hours) without discernible
progress. The drill string was recovered with the bit clearing the rotary table
at 0605 hr on 23 April. The contents of the junk baskets were examined and
found to contain angular coarse sandy basaltic chips along with a few small
(2-3 cm) sub-rounded basaltic clasts, consistent with the rocks cored when this
interval was first drilled on Expedition 309. After discussing options with the
onboard scientific leadership, it was decided that placing a cement plug at and
above the bridge could possibly stabilize the zone and allow us to advance past
A cementing assembly was made up of the used Reed 9 7/8"
tricone bit without jets and two stands of drill collars and deployed. Hole
1256D was reentered for the third time at 1520 hr on 23 April. After the
driller tagged the bridge with the bit at 922 mbsf, the circulating head was
made up to the drill string and tested to 1500 psi. Five barrels of 16 ppg
(pounds per US gallon; S.G. ~1.9) blended cement was then pumped into the hole
and chased with a column of seawater equal to the volume of the drill string.
The drill pipe was then pulled back to 807 mbsf where an additional seawater
flush consisting of 3 drill string volumes was pumped through the system.
After rigging down the cementing equipment, the drill pipe
was recovered with the bit clearing the rotary table at 0515 hr on 24
April. The Reed bit was replaced
with a new 9 7/8" tricone bit (Atlas HP61) and the drill string was deployed to
1596 mbrf. Hole 1256D was reentered for the fourth time at 1655 hr. We are
presently running in with the drilling assembly.
The week commenced with an intensive series of introductory
science meetings to highlight the cruise objectives and team sessions for the
various groups to familiarize themselves with laboratory procedures and
equipment. With a healthy mix of experience aboard, numerous training sessions
have been run (e.g., curation, imaging, microscopy) by the technical
specialists supplemented by ongoing mentoring by seasoned scientists. The
logging groups and geochemistry prepared for the planned initial wireline
In anticipation of the recovery of plutonic rocks the
science party has been adapting and enhancing description protocols to enable
the capture of igneous and alteration petrologic and structural observations.
This work built on the templates developed at the pre-cruise core-logging
meeting held at TAMU in March 2011. The science party then received training in
using the DESClogik data capture application and database system. The archive
and working halves of cores recovered on Expedition 312 from the dike-gabbro
boundary and below are aboard, and these have been used to further refine the
core logging templates. The archive halves are presently being systematically
logged by the petrological groups. This will help tune the data capture systems
and create a seamless observational record from the Expedition 312 cores to
those recovered on this cruise. Daily science seminars on the formation and evolution of mid-ocean
ridges from ocean floor and ophiolite perspectives have been held, with
presentations to date principally lead by early career researchers. Calm seas,
beautiful sunshine and Expedition 335's first barbeque on Sunday helped assuage
a growing hunger for fresh core.
Education and Outreach
Following a successful press conference with Costa Rican
media as well as ship tours for ~60 visitors during the port call, the science
party received a presentation on education and communication outreach,
including the impact of embargo policies of major peer-reviewed journals and
the IODP 1-year data moratorium. The science party was also given blogging and
social media guidelines and was encouraged to sign up to blog on the JR.org
site and/or to help recruit schools to participate in the ship-to-shore video
broadcasts. First blogs were published on the JR.org site, including an
illustration prepared by the shipboard scientific illustrator as part of her
duties to develop a portfolio of ocean crust accretion diagrams for Expedition
335 and the wider ocean lithosphere community.
Technical Support and HSE Activities
Science Mission Support: The Science Party members were
introduced to their labs, met technical staff, and trained on data systems and
instrument host software. Seafloor magnet and bathymetric data were collected
during our transit from Puntarenas to our first site. The WSTP downhole tool
was prepared to sample borehole fluids. Other technical activities included:
- Continued development for DESCLogik project.
- Installed and tested new pyncometer interface board.
- Moved excess furniture into DOD van for shipment back to College Station.
- Installed new counter top in the Planning Area and re-plumbed coffee machine.
- ODL engineers started investigation into Core Lab exhaust ducting issues.
- Relocation and clean up work for science pallet storage reorganization.
- Troubleshooting aft VSAT installation.
- Loaded emergency D-tube supplies into the aft "Bat Cave" storage.
- Installed and tested the whole round imaging tray, developed measurement protocols.
The science party and new technical staff completed Transocean's
safety induction and IODP's Lab Safety Tour. The weekly fire and abandon ship
drill was held as scheduled.