The ship was offset ~20 m west of Hole 1150A and a jet-in test was conducted for the future emplacement of the reentry cone and 20-in casing string. The jet-in test was completed in 2.5 hr after washing without rotation to a depth of 67.0 mbsf. A hard layer was detected at 56.0 mbsf, though increased weight on the bit and circulation kept the drill bit advancing without any problem. The jet-in test was concluded at 1830 hr 26 June when the bit cleared the seafloor.
The APC/XCB core bit reached the rig floor at 2215 hr 26 June 1999 ending Hole 1150A and beginning Hole 1150B. The bit was found to be in excellent condition after accumulating a total of 23.2 rotating hr and 913.8 m of penetration.
Hole 1150B was spudded ~44 m east of Hole 1150A at 0415 hr on Sunday 27 June with the rotary core barrel (RCB) coring system in a water depth of 2680.8 m (2692.2 mbrf). The hole was drilled down to 703.3 mbsf before coring began. Drilling was briefly halted during this interval when a hydraulic line in the top drive umbilical ruptured. Extremely heavy rain and high wind hampered the repair effort, which took 1.5 hr. Overall, drilling and connection time was 19.75 hr, with an average ROP of 35.6 m/hr.
RCB coring was initiated about two cores above the XCB termination depth of 722.6 mbsf. We had originally planned to core to 1000 mbsf but continued deeper in search of more indurated sedimentary rock, which would be better suited for the borehole instruments planned for installation in Hole 1150C. In addition, we wanted to get deep enough to log through the rock units directly below and at the depth at which the borehole instruments were to reside. Coring ceased at 1181.6 mbsf on 1 July, when it was deemed that the lithification and depth was sufficient to accomplish our goals. In all, we cored 478.3 m and recovered 269.4 m of sediment and sedimentary rock from 50 RCB cores, for an average recovery of 56.3% (Table T1).
No hydrocarbon problems were experienced in this hole. Methane gas continued to be present in the cores at an average of ~3%, slightly higher than the average of 1.5% seen in Hole 1150A. Ethane was present at ~10 ppm, and no higher hydrocarbons were identified.
In preparation for logging, we completed a wiper trip, circulated a 30-bbl sepiolite pill, released the bit, displaced the hole with 330 bbl of sepiolite logging mud, and pulled the bottom of the drill pipe up to ~114 mbsf. Though we encountered no apparent restrictions during the wiper trip, the first logging run encountered a tight interval at ~643 mbsf, which we were unable to get through. Logging with the triple combination logging tool (triple combo) string proceeded upward from 646 mbsf. The second logging run, using the Formation MicroScanner (FMS) tool string, encountered a second obstruction, this time at ~473 mbsf, and the hole was logged upward from this depth. After completing the first two logging runs, we lowered the drill string to 742 mbsf. No resistance was identified by the driller. This allowed three logging runs—the triple combo, FMS, and borehole televiewer (BHTV) runs—to reach to within 7 to 11 m of the bottom of the hole. Formation MicroScanner data indicated an elliptical hole with one axis diameter measuring 10 in, the other measuring 14 in.
The wireline logging tools and sheaves were rigged down by 0600 hr 3 July, and the drill string was pulled to a depth of ~3292 m (~600 mbsf). A 30-bbl cement plug (~96 m long) was set at that point to ensure that there would be no communication of seawater downhole and through a fracture network to the reentry installation. The drill string was pulled clear of the seafloor at 0900 hr 3 July, and the drill string was flushed with seawater to remove any remnant cement.
While recovering the drill string the drillship was offset ~80 m west, which was ~40 m west of Hole 1150A. The end of the drill string reached the rig floor at 1330 hr on 3 July 1999, ending Hole 1150B and beginning Hole 1150C.
The upper guide horn was removed to assemble the 20-in casing string and reentry cone ensemble (Fig. F3). Assembly of the 20-in casing went exceptionally well, taking only 2.5 hr to join the shoe joint, three additional joints of casing, and the Dril-Quip running tool.
With the reentry cone positioned beneath the rotary table on the moonpool doors, we attempted to lower and latch the 20-in casing hanger into the reentry cone. The first sign of trouble occurred when the hanger landed at the base of the reentry cone panels rather than proceeding smoothly into the bore of the transition pipe. Even after jostling the cone around the hanger, the hanger continued to hang up sporadically in the transition pipe and would not move freely down to the landing shoulder. We decided that there must be a significant interference between the 20-in casing hanger body and the weld attaching the latch-ring body extension. To save time, the top joint of 20-in casing was laid out with the hanger attached. The next joint of 20-in casing was also laid out. The third and fourth joints of casing plus casing shoe were raised up into the derrick, allowing access to the reentry cone. The cone was then repositioned onto its side to allow a more detailed inspection. After inspecting the transition areas of both reentry cones aboard, it was apparent that the axial weld on the transition pipe and the weld attaching the transition pipe to the latch-ring body extension protruded far enough to prevent the casing hanger from traveling freely to the landing shoulder. Also, field measurements show that the uppermost ~1 in of the latch-ring body extension was incorrectly machined. Once the welds and the incorrectly machined portion of the latch ring were ground flush on the inside diameter, the casing string was once again assembled; this time the casing hanger latched into the proper position as designed. This incident resulted in 8.5 hr of lost time.
The casing string and reentry cone were lowered to a depth of 2654 m, and the subsea camera on the vibration-isolated television frame (referred to as VIT camera herein) was deployed during the pipe trip. Hole 1150D was spudded at 0930 hr on 4 July by jetting the casing into the seafloor. It took 4.25 hr to jet in the casing to a depth of 58.13 mbsf and land the reentry cone at the seafloor at a depth of 2692.2 m.
The pipe was tripped back
to the rig floor, where the nozzles on the bit were replaced and the bottom-hole
assembly (BHA) was assembled in preparation for drilling the 18.5-in diameter
hole. The first reentry into the cone was made at 0245 hr on 5 July. By 0145 hr
on 6 July, we had drilled the 18
-in
hole down to a depth of 539.8 mbsf, for an average drilling rate of 27.5 m/hr.
The hole was swept clean with two 50-bbl sepiolite pills and a wiper trip,
displaced with 550 bbl of sepiolite, and the drill string pulled out of the
hole, reaching the rig floor at 1245 hr.
The 30-m-long seagoing tug Fumi Maru #26 came alongside to discharge cargo and seven passengers at 0600 hr on 6 July. Arriving personnel included Masanao Shinohara from the Earthquake Research Institute of the University of Tokyo (shipboard participant), Kevin Sharp (cable-connector technician from Ocean Design), Andrew Green and Murray McGowan (seismometer technicians from Guralp Systems Ltd., United Kingdom), and Michael Acierno (computer specialist from Carnegie Institution). In addition, a two-man film crew (Satoru Ninomiya and Daisuke Yamada), hired by ORI, came aboard. The film crew and the two Guralp technicians departed the ship the following day at 1200 hr after their work was completed.
The rig crew ran the 42 joints (525.87 m) of 16-in casing, assembled the casing hanger, and engaged the Dril-Quip running tool in only 5.5 hr. The 16-in casing string was lowered to the seafloor, and the second reentry occurred at 0130 hr on 7 July. The casing began to show resistance almost immediately upon entry into the 20-in conductor pipe. The circulating head had to be installed, and the casing was circulated down to 137.8 mbsf. While running the casing into the bore hole, weights of 20-30 kilopounds (kips) were used to advance the casing string. By 0845 hr on 7 July, the casing hanger was landed. The casing was cemented using 30 bbl of cement, which should have resulted in cement reaching ~100 m up the exterior of the 16-in casing. The cementing dart was launched, and at 1015 hr the plug was landed at the cementing shoe and confirmed with 500-psi pump pressure. Within 15 min, the running tool was released and the drill string was then flushed with seawater to remove any residual cement in the drill string. The pipe was pulled out of the hole clearing the rotary table at 1600 hr on the same day.
After attaching a new 14
-in
drill bit, the drill string was lowered and the cone reentered at 2315 hr on 7
July. Because the bit was hanging up and not sliding smoothly into the
transition pipe, the bit was pulled clear of the reentry cone at 2345 hr and the
top drive was picked up to allow the pipe to be rotated. The reentry cone was
reentered once again at 0030 hr on 8 July. The bit was "rolled" gently
into the transition area. The 16-in cementing shoe was contacted at a depth of
527 mbsf, and we began drilling out the cementing shoe, wiper plug, and dart
assembly.
Drilling had been in progress for 2.5 hr when, at 0640 hr, 60,000 lb of string weight was suddenly lost along with 300 psi of pump pressure. Calculations indicated that the drill string had parted at or near the seafloor. The VIT camera was deployed to verify the position of the fish (the part of the drill string in the hole) in relation to the reentry cone. The top of the fish was not visible. The camera showed, however, that the 5-in drill pipe had parted ~1 m below a tool joint in the area where the tube of the pipe had been rubbing the casing hanger during the cement-shoe drilling operation. Once the drill string was at the surface it was verified that the string did part in the 5-in drill pipe, 0.98 m below a box tool joint. The pipe showed signs of rubbing against the hanger or the transition pipe of the reentry cone during rotation but still measured a full 5 in in diameter. The pipe coating was worn away, but no deep cuts or gouges were noted. The failure was a clean break with no metal extending over the diameter of the pipe.
To retrieve the fish, we
used fishing tools consisting of a 8
-in
diameter overshot with a 5-in basket grapple and an 8 -in
diameter wall hook guide. The fish consisted of the BHA assembly plus 13
stands of 5-in drill pipe for a total length of 526.5 m. The top of the fish was
calculated to be at 2693.3 m, which put it near the top of the 16-in casing
hanger. The fishing assembly was made up and run into the top of the reentry
cone. On the first two attempts to engage the fish, the overshot slid down
beside the fish in the 15
-in inside diameter casing. On the third attempt, the guide passed over the top
of the fish and the grapple engaged the 5-in drill-pipe tube. The fish was
pulled to the surface and the broken joint was removed.
At 1045 hr on 8 July, Hole
1150C was reentered. As on the previous reentry, the bit once again hung on the
lip of the reentry cone at the entrance to the transition pipe. This time, chain
tongs were used to rotate the pipe and it eventually slipped into the throat of
the reentry cone. The pipe was run to bottom, and at 1245 hr we once again began
drilling operations. At 1400 hr on 10 July, we finished drilling the 14-in
hole for emplacement of the 10-in
casing string. It took 24.25 hr to drill the 510 m of 14-in
hole down to a depth of 1050.0 mbsf, an average rate of 21 m/hr. Sepiolite mud
sweeps of 30 bbl every 40 m were pumped during the drilling process, and the
hole was circulated with a 50-bbl sepiolite pill. The pipe was tripped to the
rig floor at 0245 hr on 11 July.
-in Casing StringThe 10-in
casing string, consisting of 82 joints of 10-in
casing plus the casing hanger, was assembled in just 8.75 hr. The casing string
was lowered to the seafloor, and Hole 1150C was reentered at 1735 hr on 11 July.
An hour was spent attempting to advance the casing shoe through the throat of the reentry cone without success. The bit was pulled clear of the reentry cone at 1630 hr, and the top drive was picked up. The cone was reentered after 35 min of ship maneuvering, but the problem persisted. As the casing string was lowered, the casing shoe would catch and cause the casing string to bend or bow with as little as 5000-8000 lb of weight. We observed the deflection of the casing string with the subsea camera, which moved off center of the hole when weight was applied to the shoe. On previous reentries the same problem had occurred entering the transition pipe/casing hanger area but had been solved with rotation that allowed the bits to pass. Because the Dril-Quip running tool released with right-hand rotation, we planned left-hand rotation to work the casing shoe through the transition pipe/casing hanger area. The top drive torque limit was set at 150 A (~2000 ft-lb) to prevent overtorquing the running tool and to keep the reverse torque well below the make-up torque of the casing (4200 ft-lb). Very slow reverse rotation was initiated, and the pipe was worked in an attempt to pass. Because of the low torque limit setting, rotation stopped as soon as the casing shoe took weight and never approached the make-up torque of the casing. Rotation at the reentry cone matched the rotation at the surface. The casing string was worked with and without rotation with weights reaching 12,000 lb during vessel heaves. The vessel was also offset 20 m forward at this time to try to reposition the casing in relation to the cone.
At 1750 hr on 11 July, the string parted in a casing coupling 17 joints (~205 m) above the casing shoe. Part of the casing was observed falling down through the previously impassable transition pipe and into the hole (Fig. F4). The VIT camera was recovered and the remaining 67 joints of casing were pulled to the rig floor. Several days later when we returned to Hole 1150C to plug it with cement, we observed some of the lost joints lying on the seafloor.
After reviewing the operation, the failure of the casing coupling was attributed to the flexing and bending of the casing string. This may have been caused by flaws in the reentry cone. As noted earlier in the leg, when trying to land the 20-in casing hanger in the reentry base used on Hole 1150C, we observed that the landing-ring body extension welded to the transition pipe was machined improperly and that the welds inside the pipe were not dressed to specifications. When the same machined area on the reentry cone for Hole 1150D was ground flush, we noticed that the body extension was not welded properly, creating a serious weakness to the structure. If the same welding techniques were used on the base of the reentry cone for Hole 1150C, the weld could have failed, creating an opening between the casing hangers and the transition pipe welded to the bottom of the base. This could have been the cause of the difficulties getting the bits and casing shoes to pass through the transition pipe/hanger area. This also could have been the problem that led to the drill-pipe failure that occurred while we drilled out the 16-in casing shoe.
Considering the rapid rate at which the casing string dropped into the hole, there would have been a slim chance of removing the pile of metal that would have crashed at the base of the hole. There was also concern that even if we were able to fish the casing, we might not have been able to pull it through the flawed reentry cone. Thus, we abandoned operations on Hole 1150C and started over in Hole 1150D.
Operations at Hole 1150D began with a great deal of welding and grinding to bring the reentry cone up to required tolerance and strength specifications. A total of 14 hr was required before the reentry cone could be positioned in the center of the moonpool doors. In the meantime, the ship was offset 60 m south of Hole 1150A.
Four joints of 20-in casing (including the shoe joint) were assembled and attached to the 20-in casing hanger. The hanger was lowered into the reentry cone and engaged the reentry cone as designed without incident. Hole 1150D was spudded at 0545 hr on 13 July at a seafloor depth of 2692.2 m. The cone landed at the seafloor 11 hr later, positioning the 20-in casing shoe at a depth of 55.0 mbsf.
The drill string was
pulled back to the ship, and we changed out the No. 16 jets with No. 24 jets in
the 18-in drill bit. The
BHA was assembled and the drill string was run back to bottom. The first reentry
was made into Hole 1150D at 0345 hr on 14 July after maneuvering the vessel for
45 min. This time the bit slid smoothly into the throat of the reentry cone and
continued to the casing shoe with no resistance. We drilled the hole to a depth
of 544.8 mbsf at an average penetration rate of 35.7 m/hr. Following bentonite
mud sweeps, a wiper trip, and a hole displacement with sepiolite mud, we tripped
the drill string to the rig floor.
By 1230 hr on 15 July, the drill crew had assembled 41 joints of 16-in casing. Reentry was made at 1700 hr on 15 July without requiring any time to reposition the vessel. The 16-in casing shoe went through the reentry cone transition with no problem, and the string was advanced to a depth of 278 m before the top drive was picked up. The remaining portion of the casing string was "washed" to bottom in the relatively tight hole. The 16-in casing shoe was landed at 533.9 mbsf at 0100 hr on 16 July and cemented into place with 30 bbl of cement 15.8 lb/gal (~1.92 g/cm3). The drill string was recovered to the rig floor by 0745 hr on 16 July.
After positioning the ship
for 30 min, Hole 1150D was reentered at 1315 hr on 16 July with the 14-in
drill bit. As before, the bit went straight through the reentry cone transition
area and advanced to bottom, where the cementing shoe was tagged at a depth of
532.8 mbsf. By 0830 hr on 17 July, the hole was drilled to a depth of 1044.8
mbsf. Only 16 hr was required to drill the 500 m of hole at an average ROP of
31.3 m/hr. As before, the hole was circulated with a 50-bbl bentonite mud sweep,
and a wiper trip was conducted up to the 16-in casing shoe.
-in Casing StringIt took ~7.5 hr to
assemble 80 joints of 10-in
and the casing hanger. The casing string was lowered, the VIT camera was
deployed, and at 0800 hr on 18 July, after positioning the ship for 30 min, Hole
1150D was reentered for the fourth time. Unlike the difficulties we had at Hole
1150C, this time the 10-in
casing shoe slipped through the throat of the reentry cone without resistance
and we ran the string to 1044.8 mbsf and then cemented with 50 bbl of 15.8
lb/gal cement.
During this operation, we had been monitoring a storm system that was heading in our direction. To avoid the possibility of being caught in a storm while deploying the borehole instruments, we decided to delay the deployment and instead head to Yokohama to get additional casing and a reentry cone, which were needed for Site 1151 operations. The drill pipe was tripped to the surface, the rig floor was secured for transit, and the ship got under way at 2130 hr on 18 July.
The 370-nmi distance to
Yokohama was covered in 36.8 hr at an average rate of 10.3 kt. The pilot came
aboard at 0750 hr, and we proceeded dockside with the first line ashore at 1000
hr on 20 July. Even though it was a Japanese holiday called "Day of the
Oceans," the resupply went exceptionally well. The shipping agent, Kiyoaki
Chiba of Sea Trade & Agency Inc., was able to arrange for a forklift and
foreman to remain on duty to assist the ship's crew with continued loading
activities after normal holiday working hours had ended. In addition, loading
was expedited by having the cargo predelivered dockside before our arrival.
Cargo taken aboard included one reentry cone, 6 joints of 16-in casing, 48
joints of 10-in casing,
and 32 joints of 4-in
casing. In addition, Michael Acierno and Kevin Sharp both departed the vessel
since their work was completed. Dan Malone, Overseas Drilling Ltd., warehouseman
replacement for the retiring Mick Malone (on the other crew), came aboard to
spend the rest of the leg coordinating with Mike Cole, the warehouseman on the
Leg 186 crew. All loading was completed by 1800 hr, although we were unable to
depart right away because of harbor congestion associated with the holiday
fireworks display. The delay provided a chance for all on the JOIDES
Resolution to enjoy nearly 2 hr of fireworks and some much-needed
entertainment along the dock. We eventually secured both pilots required for
transit out of the port area and departed at 2145 hr on 20 July.
The 364-nmi transit back to Site 1150 took 31 hr at an average rate of 11.7 kt. We acquired the positioning beacon at 0700 hr the morning of 22 July.
In exceptionally calm
seas, we reentered Hole 1150D. Using a 9 -in
tricone drill bit, we drilled through the cementing shoe at a depth of 1031.8
mbsf and began drilling the 9
-in diameter hole. Drilling in Hole 1150D was completed to a depth of 1140.0
mbsf. The final 95.2 m of hole took 5.5 hr to drill at a rate of 17.3 m/hr. We
circulated the hole with a 50-bbl bentonite gel mud sweep and commenced the
wiper trip back to the 10-in
casing shoe. We completed the trip back to the casing shoe without incident,
though on the return back down we experienced 20-30 kips of drag almost from the
start. Torquing and elevated pump pressure were also apparent. After we reamed
the hole to bottom twice and circulated two additional sepiolite pills, the hole
seemed to be clean.
At 1315 hr on 23 July, we
began pulling out of the hole to the seafloor. We cleared the reentry cone at
1530 hr and offset the ship back to Hole 1150C to plug the open hole with
cement. During the move between holes we identified a string of 10-in
casing resting on the seafloor near Hole 1150C. As discussed above, the 10-in
casing string at Hole 1150C apparently failed in more than one place, which
allowed some casing to fall into the reentry cone and some to fall outside onto
the seafloor. We were not able to accurately determine the quantity of casing
outside the reentry cone.
At 1630 hr we reentered Hole 1150C and, as anticipated, had to rotate the drill bit with the top drive to pass through the cone transition area. Because we had made five flawless reentries into Hole 1150D, we can now definitively rule out environmental causes for the reentry problems experienced in Hole 1150C. Therefore, there must be a major structural problem or failure in the transition area of the Hole 1150C reentry cone. The pipe was advanced to a depth of 263.0 mbsf, and a 15-bbl plug of cement was pumped into the 16-in casing. This was to prevent flow between Hole 1150C and Hole 1150D, where the instrument string was to be emplaced. At 1845 hr, after displacing the cement plug, the pipe was pulled clear of the Hole 1150C reentry cone. The pipe cleared the rotary table at 2230 hr, and preparations began for deployment of the instrument package in Hole 1150D.
The ship was offset back
to Hole 1150D as the rig floor was prepared for handling the instruments. The
instrument string was assembled by its various parts, of which the lowest is a
stinger pipe, a tube that allows cement to be pumped below the instruments (Fig.
F3). The stinger
is bolted to a overlying strainmeter. Above this is a deployment frame with two
seismometers and a tiltmeter. This part of the instrument package was lowered
into the moonpool area below the rig floor where the four -in
diameter instrument cables were connected to the respective instruments. The
rest of the instrument string consisted of 4-in
casing, a circulating sub, and a riser/casing hanger. Ninety-five joints
(~1107.1 m) of 4-in casing
were run while strapping and taping the instrument cables with tie wraps and
duct tape. In addition, casing centralizers were installed ~7.0 m apart along
the casing. After deploying 40 joints of casing, the circulating sub, which
allows the drill string to be flushed after the instruments are cemented in
place, was installed. Then the other 55 joints of 4-in
casing were assembled with cables being attached in the same manner. The last
two joints were not taped because this portion of cable was to be removed later
to allow the watertight connectors to be installed in the subsea shop.
After running all of the 4-in
casing, the J-slot
running tool was assembled, and the riser and casing hanger were picked up and
connected to the top joint of 4-in
casing. The assembly was then lowered into the moonpool area, where the
instrument cables were measured and cut to length. The riser was pulled back up
to the rig floor while the cable ends were fed into the subsea shop for
installation of the watertight connectors, a process referred to as cable
termination.
The cable termination began at 1945 hr on 24 July and extended until 1030 hr on 25 July. By 1200 hr the multiple-access expandable gateway (MEG) had been installed into the specially designed riser carrier, and the four cables and their new connectors were plugged into the MEG. The MEG is composed of a combiner/repeater module, analog-digital converter modules, strainmeter interface module, and power conditioning/distribution module, all of which acquire signals from the sensors, convert analog signals to digital data, and send out the converted digital data to recorders via a single serial link. By 1300 hr, the final instrument checks had been completed. Once the riser/hanger was lowered beneath the ship, the VIT camera was deployed over the running tool/riser/casing hanger assembly to ensure that there was no interference. The VIT was recovered after the successful test, and we commenced tripping the drill string to seafloor.
After positioning the ship
for 1 hr, we reentered Hole 1150D at 1730 hr on 25 July. The reentry drill
string was spaced out so as to allow the entire 16-m instrument package to be
inserted completely into the throat of the reentry cone with the top of the
instruments below the 10-in
casing hanger. The bottom of the instrument string was then lowered to a depth
of 1032 mbsf, where the top drive was picked up in preparation for inserting the
instrument package into the borehole. Slow circulation was maintained as the
package was lowered into the open 9 -in
hole so that we would know immediately if the end of the stinger began to plug.
Resistance was met almost immediately after entering the open hole. Washing
continued for 3.5 hr as the package was advanced to a depth of 1101.8 mbsf, or
23.4 m short of landing the riser/casing hanger in the reentry cone. Throughout
the insertion period we experienced 10-20 kips overpull or drag and pressures of
as much as 1500 psi. When making connections with each new pipe joint, the hole
would close around (pack off) the stinger or the stinger would become plugged.
Casing advance proved impossible until pump pressures returned to normal.
Several times the casing had to be picked up and worked back down again. This
frequently failed to lower the pressure, indicating the stinger pipe was
probably still plugged. Our efforts to emplace the instrument package were
further aggravated by a leak path that was apparently coming from the J-type
running tool. This made it difficult to determine how much circulation was going
out the stinger and how much was leaking past the running tool. Mud sweeps did
not improve the situation. At 2400 hr on 25 July, we elected to pull the
instrument string back inside the casing shoe. At this point, the stinger was
completely plugged, and increasing the pump pressure did not unplug it.
It was obvious that we needed to reenter the hole with a drilling assembly and ream out the ~100 m of open hole before we had any chance of successfully inserting the instrument package. Fortunately the stinger unplugged itself during the pipe trip, eliminating another potentially serious problem. The final step was to check the status of the instruments once the riser was pulled into the moonpool area. To our relief, all of the instruments were functioning. Given their multiple trips up and down the tight part of the open hole and their trip through the casing and reentry cone, the instruments and cables proved to be quite robust.
We decided to attempt to
hang off the intact instrument string from the ceiling above the moonpool rather
than undertake the enormous job of re-spooling the cables, removing the tape,
tie wraps, and centralizers, breaking down the 4-in
casing string, and disassembling the stinger/strainmeter/seismometer/tilt meter
instrument package. We were able to attempt this nonstandard operation because
of very calm weather and sea conditions and because the hang-off loads were
relatively low at ~20 T. To allow hanging off the instrument string we had to
make some modifications to the riser/hanger stabilizer fins. These were cut back
~18 cm (~7 in) to install the 10-in
casing elevators with the 10-in
casing slips installed below. We then disengaged the running tool and set it
aside for inspection and repair. Four 1-in-diameter
wire slings were attached to the 10-in
elevators and connected to the blocks. As the blocks were lowered, the load was
slowly transferred from the lowering slings to the hang-off slings. This allowed
the ~1130-m-long instrument string to swing slightly forward in the moonpool
where it was secured with a tugger line (Fig. F5).
The transfer was completed in 5 hr (including riser/hanger modifications), and
the rig floor was then clear for pipe handling/drilling operations to continue.
In addition to the hang-off activities, the wash pipe in the running tool was
welded at the top end to eliminate a circulation leak path within the J-type
running tool.
A 9
-in tricone drill bit was assembled with two stands of drill collars and the
normal 5-in transition
pipe. We lowered the pipe to bottom and reentered Hole 1150D at 1730 hr on 26
July. We reamed out the hole by making several passes through tight spots and
circulated several 30-bbl sepiolite mud sweeps. This was followed by a wiper
trip, circulating 5 m of fill from the hole, and then displacing the hole with
40 bbl of sepiolite mud.
We pulled out of the hole clearing the reentry cone at 0515 hr on 27 July and proceeded pulling pipe until clearing the rotary table at 0900 hr. Within 2 hr, the instrument string was transferred back to the running tool and a final instrument check was performed. The pipe was then run to bottom, and Hole 1150D was reentered for the eighth and final time at 1630 hr on 27 July.
This time the string entered the open hole with little resistance; however, after three pipe joint connections the drag and elevated pump pressure once again became our nemesis. As before, when a connection was made the string would pack off and high pump pressure was required to initiate circulation. Despite the repairs made to the running tool, we were faced with a circulation leak. We worked the pipe and unplugged the stinger multiple times, and after 3 hr we successfully landed the riser and casing hanger in the reentry cone, placing the end of the instrument string stinger at 1122.8 mbsf.
We pumped 80 bbl of 15.8 lb/gal cement, displacing it with the rig pumps. The cementing dart landed in the circulating sub located ~455 m above the instrument package and the sleeve sheared as designed at ~1500 psi. This opened up circulation ports to the annulus and allowed the drill string to be thoroughly circulated (two times capacity) to remove any remaining cement. The VIT camera was recovered, and at 0045 hr on 28 July we began to rig up for assembling the battery frame halves on the moonpool doors.
The battery frame halves were bolted together around the pipe on the moonpool doors. Final deployment rigging and release bridles with dual acoustic release systems were attached. We waited until daylight to deploy the assembly through the moonpool because of the intricate rigging required and the poor visibility at night within the moonpool. We did not want to risk snagging a deployment cable on the guide horn. After waiting until 0430 hr (~45 min) we began to lower the platform through the moonpool. This intricate operation was completed quite well, partly because of the relatively calm sea state, although there was some surge within the moonpool.
The battery platform was lowered at ~3500 ft/hr using the logging line, and, at 0830 hr, the assembly landed in the reentry cone. Within 10 min, a portable command unit was used to send a 10-kHz acoustic signal to the release system. After recovering the logging line and the remaining deployment bridle equipped with acoustic releases, the VIT camera was deployed. At 1145 hr we verified that the battery platform had indeed been placed exactly in position as planned (Fig. F6). All cables and surface gear appeared to be in good condition, undamaged by the deployment process.
It took ~1 hr to actually release the J-type running tool from the riser, keeping the entire drill crew and science party on edge. At 1245 hr on 28 July, while working the tool through the neutral point and with ~200 A torque, the running tool abruptly released from the riser/hanger. This completed the instrument installation for Hole 1150D.
During the pipe trip to the rig floor, both positioning beacons were released and recovered aboard, the rig floor was secured for transit, and at 1900 hr on 28 July the ship got under way for Site 1151.
The weather was quite variable during operations in Hole 1150B. At no time was the operation halted because of weather, though conditions did deteriorate markedly during the passage of a low-pressure cell northwest of the drilling location. We began to experience the effects of one low-pressure cell on the afternoon of 30 June, which continued through midday on 1 July. At its worst this gale brought sustained winds of 42 kt gusting to 56 kt, 28-ft seas on 7-s periods, and 30-ft swells on 7- to 8-s periods. The maximum roll, pitch, and heave experienced was 5°, 4°, and 9 ft, respectively.
Weather while drilling Hole 1150C was moderate and did not influence operations. The climate was characterized by frequent fog, overcast skies, frequent rain showers, and cool temperatures.
Weather and sea state were both excellent during operations at Site 1150D. The concern that a tropical depression was going to cross the site before installation of the instrument string influenced us to head to port earlier than would have been ideal. The storm appeared to dissipate as it neared the site, though we have no idea what its final effect on the site was since we were in Yokohama then.
