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IODP Expedition 327:
Juan de Fuca Ridge-Flank Hydrogeology
Week 7 Report (16-22 August 2010)
PDF file is available for download.
23 August 2010
Operations
Hole U1362A L-CORK Instrument String Deployment
Following the discovery that
the instrument string was protruding by several meters beyond the end of the
CORK stinger, it wad decided to bring the drill string back to the surface. At
0200 hr on 16 August the L-CORK was hung off in the moon pool. The instrument
string was released using the screws built into the system for future removal by
a submersible, the string was shortened by 10.17 m, and then it was reinserted
into the L-CORK. At 0600 hr the drill string was once again tripped to the
seafloor. The trip took longer than usual because the pipe had to be filled
from a water hose after assembling each stand. The water was needed to prevent
a differential pressure from building up and overloading the latch system on
the instrument string. Hole U1362A was reentered for the eleventh time at 1150
hr. The CORK was landed without incident and the inflatable packer assemblies
were inflated with 1500 psi pressure over a period of 30 minutes. The Vibration
Isolated Television (VIT)/subsea TV was recovered and at 1600 hr preparations
began for deploying the CORK platform. The platform halves were maneuvered onto
the moon pool doors and bolted together. Another 2 hr were spent assembling the
"lunar lander" deployment vehicle with the VIT sleeve and rigging the various
required slings. At 1800 hr the platform began its trip to the seafloor but at
2007 hr the subsea TV camera went black. After some initial trouble shooting by
the ODL electronic technician, the VIT/subsea TV with the suspended CORK
platform was recovered back to the ship. A faulty connector was replaced and
the VIT was once again run to bottom. Upon initial landing at 0230 hr on 17
August, the platform reached the CORK running tool but failed to release. After
working the platform up and down for ~1 hr the platform eventually released.
The VIT was recovered back to the ship and the "lunar lander" was removed along
with all platform deployment slings. This was done so they would not become
entangled with the L-CORK installation. The VIT/subsea TV was deployed back to
bottom, confirming that the platform had not released correctly, and was found
to be hanging at an angle off the CORK running tool. The VIT sleeve was set
down on the platform multiple times before the platform was jarred off and fell
into position on the rim of the reentry cone. The running tool was released
from the L-CORK head at 0600 hr on 17 August, successfully completing the
installation of the Hole U1362A L-CORK. The drill string was tripped back to
the surface and the recovery tool cleared the rig floor at 1045 hr, ending
operations at Hole U1362A. Close inspection of the "lunar lander" mechanism and
the CORK running tool indicated that one of its arms was bent due to impact
with the bolt screwed into the running tool to protect the packer inflation
hose fitting. As a result only two of the three arms released initially, causing
the platform to hang on the third arm and resulting in the cocked attitude of
the platform on the CORK head. A shorter bolt that will not interfere with the
"lunar lander" mechanism was installed for the next deployment.
Hole U1301B Instrument String Recovery and Replacement (Expedition 301)
A new bottom-hole assembly
(BHA) that included the CORK recovery tool was made up and tripped to the
seafloor by 1615 hr on 17 August. At 1730 hr the recovery tool engaged the Hole
U1301B CORK head but before the J-tool could be engaged the running tool heaved
off. This required a second engagement attempt and by 1815 hr the tool was back
on the CORK head. Engagement of the J-slot tool was ineffectual so 10,000 lbs
weight was applied to the top of the CORK. The sinker bars were lowered and
after multiple attempts the GS overshot engaged the instrument string top plug.
Although tension was applied to the instrument string, the instrument string
appeared to be stuck in place. After working the sandline with various degrees
of overpull the instrument string started creeping slowly upward. At 0920 hr on
17 August the instrument string parted. The CORK recovery tool was disengaged
and a portion of the instrument string was recovered back to the surface. Upon
recovery it was found that a splice in the Spectra rope had failed directly
above the middle plug of the installed instrument string. Five temperature data
loggers and 377 m of Spectra rope were recovered. After laying out the
recovered portion of the instrument string the CORK head was re-engaged at 2225
hr. Another sandline run was made to deploy temperature data loggers to obtain
a temperature profile of the remaining portion of the hole as well as determine
the depth of the available open hole. This allowed proper configuration of the
replacement instrument string. The bottom of the open hole was ultimately
tagged at 3037 m (370 m below seafloor). The recovery tool was disengaged once
again at 0130 hr on 18 August. Make-up of the replacement instrument string began
at 0145 hr. This included the rigging of the Schlumberger electric logging
line. The new Electronic Release System (ERS), under development by Stress
Engineering for use with the developmental SCIMPI CORK system, was used for
this deployment since the Hole U1301B CORK system was not configured with an
instrument string latch-down system. Historically there have been a lot of
problems jarring off the instrument string without dislodging the upper
landing/seal sub. Therefore it was hoped that the ERS system would work. The
replacement instrument string was ready for deployment at 0330 hr and the CORK
running tool was engaged once again at 0435 hr. The instrument string was
successfully landed and released using the ERS without incident and the
Schlumberger logging line was recovered and rigged down. At 0530 hr on 18
August the CORK recovery tool was disengaged for the final time and the ship
began offsetting in dynamic positioning (DP) mode to Hole 1027C.
Hole 1027C CORK Recovery and Replacement (Leg 168)
At 1000 hr on 18 August the
CORK recovery tool was slipped onto the Hole 1027C CORK head and by 1015 hr
engagement of the J-slots with the CORK lugs was verified. Another 3-1/2 hr
were spent attempting to recover the CORK without success. Ultimately it was realized
that to release this type of CORK another set of lugs further down on the CORK
head (below the CORK platform) had to be engaged. The recovery tool deployed
was not long enough to reach these latches so the drill string was recovered to
the surface while a discussion of options took place. Finally, it was decided
that the crew could fabricate the required recovery tool using the existing
tool as a starting point, which took 36 hr to complete. A test-fitting jig was
built to emulate the 1027C CORK head to be recovered, a section of 20 inch
casing was used to extend the length of the tool so it could reach deep enough
to engage the lower set of CORK latches, the lower section of the tool was
enlarged to the correct inside diameter, and the small reverse cone used to
enhance the ability to get over the CORK head was cut down to a 32 inch
diameter. Everything had to be welded back together, doubler plates were added
for extra strength, and then the tool was fit over the test jig for the final
time. The drill string was tripped to the seafloor and at 1200 hr on 20 August the new recovery tool was
slipped over the Hole 1027C CORK head. The tool was lowered down through the 48
inch hole in the center of the CORK platform and by 1245 hr the lower latches
on the CORK head were engaged with the "modified" recovery tool J-slots. The
next 3-1/2 hr were spent trying to pull the CORK but the latching mechanism
would not release. Attempts were cycled between allowing the recovery tool to
hammer down on the CORK head with 10,000 lbs to exerting an overpull of up to
100,000 lbs, again without success. At 1615 hr the recovery tool was disengaged
from the CORK head and the drill string was recovered back to the surface. The
VIT/subsea TV was recovered and at 2130 hr on the recovery tool cleared the
rotary table, ending operations at Hole 1027C and beginning operations at Hole
U1362B. The failed recovery operation changed the direction of shipboard
operations as it became clear we could not replace the Hole 1027C CORK. This meant we would likely have time for coring at one or more of the Grizzly Bare
alternate sites.
Hole U1362B Drilling and Tracer Injection Test
Once the drill
string was recovered, the BHA was changed to a drilling BHA and a new 9-7/8
inch tri-cone drill bit was deployed. Hole U1362B was re-entered for the sixth time at
0423 hr on 21 August. The bit was advanced to bottom taking weight at 172 mbsf.
The top drive was picked up at that point and the hole was washed/reamed to a
depth of 262 mbsf where the top of the major concentration of cement was
contacted. The cement was drilled out and the hole cleaned to the bottom of the
14-3/4 inch hole at 282 mbsf. The hole was then deepened another 57 m to 339
mbsf, 3 m short of the original target depth of 342 mbsf. A 50-barrel
sweep of high-viscosity mud was circulated and two successive wiper trips were
conducted from the 10-3/4 inch casing shoe to total depth. On the last wiper
trip the driller noted some resistance at 310 mbsf but this was easily passed
and 6 m of hard fill was noted on bottom. Another 50-barrel mud sweep was
circulated and at 1630 hr on 22 August the drill string trip back to the
surface began. The seafloor was cleared at 1745 hr and assembly of the
injection test BHA began at 2200 hr on 22 August.
Science Results
Core description, shipboard
sampling, and laboratory measurements continued
throughout the week. Early in the week a science meeting was held to
discuss operations at Hole 1027C. Later in the week, following the failed
recovery of the Hole 1027C CORK, a meeting was held to discuss operations at
Hole U1362B and possibly the alternate Grizzly Bare sites if time allows. CORK
specialists, engineers, and technical staff formulated a plan for the upcoming
24-hr tracer injection experiment, followed by an operations review with ODL
staff.
Core description of Hole
U1362A cores is now almost complete. A detailed vein log for all cores has been
made to document changes in secondary mineral occurrence with depth. Structural
measurements are currently being processed to correct relative dips to absolute
dips. The dominant structures within this hole are veins and joints. Thin section observations of igneous and metamorphic properties are almost complete.
Currently all observations are being summarized and interpreted for the site
report.
No new physical properties samples were
obtained. As track and thermal conductivity measurements were completed in
previous weeks, we have only the finalized P-wave and moisture and density (MAD) results to report. P-wave velocities
were measured on 71 discrete samples, yielding values of 4.3–6.0 km/s,
with an average of ~5.4 km/s. This average value is greater than the values
obtained during Expedition 301. The lowest velocity was measured on a heavily
altered sample. A test of nearby unaltered material yielded much higher
velocity, which demonstrates the influence of alteration on P-wave velocity. There is no statistically significant velocity trend with depth or velocity anisotropy depending on sample direction.
Moisture and density properties were
determined on 73 discrete samples from Hole U1362A. Bulk density ranges from
2.58 to 2.89 g/cm3 with an average of ~2.74 g/cm3. Grain
density exhibits a range of 2.66–3.16 g/cm3 with a mean of
~2.88 g/cm3. Porosity values range from 2.76% to 14.2% with a mean
of 7.9%. The highest value of porosity was made in a highly altered sample,
which also has the lowest velocity. Overall, the data clearly show P>-wave velocity and porosity to be inversely correlated.
CORK specialists analyzed the temperature data
recovered from the loggers recovered with the Hole U1301B CORK instrument
string. The data are excellent and provide confirmation that the remedial
cementing operation conducted in June–July 2009 during Expedition 321T
was successful in sealing the hole. New temperature loggers were deployed in
Hole 1027C to obtain a temperature profile. Geochemists prepared and deployed
Osmosamplers on the replacement CORK instrument string.
Remanent magnetization
measurements were made on 79 discrete pieces and on portions of 23 core
sections. Remanent magnetization measurements were completed for Hole U1362A
and the data are being analyzed. Most samples display simple magnetization
behavior and the majority have positive inclinations, indicating the
magnetization was acquired during a normal polarity period. A few samples
display a reverse magnetization, most likely a result of alteration and
remagnetization.
Outreach
Outreach Officer Jackie Kane
led a videoconference with the Toledo (Ohio) Imagination Station, followed by a
videoconference with her students at St. Ursula's Academy. A videoconference
was also held with a University of Southern California Wrigley Institute
science camp and the R/V Thompson
as it was returning from Juan de Fuca Ridge. ROV activities concluded with
morning and night ROV challenges. The outreach team and several scientists
participated in a scientific-costume making workshop led by Katie Inderbitzen.
The week concluded with the Post-2013 Drilling Program Naming Workshop that was
attended by several scientists, outreach officers, technical staff, and ship's
crew.
Technical Support and HSE Activities
HSE activities
The weekly fire and boat drill were held as scheduled.
Laboratory activities
Processing of hard rock cores
continued. All Hole U1362A sections were measured with the section half
multisensor logger. Staff continues to provide support for various science,
education and engineering projects. Laboratory projects in progress include the
following: section half multisensor logger calibration, whole core multisensor
logger software upgrade in user testing, moisture and density/pycnometer
software upgrade, and laboratory documentation updates. Minor updates were
released for several LIMS applications.
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