Operations at Site 1193 (proposed Site CS-01A) began when a beacon was dropped on site coordinates at 2200 hr on 12 January 2001. The water depth was 352.8 m based on the corrected precision depth recorder.
Hole 1193 was spudded with the advanced piston corer (APC) at 0045 hr on 13 January and established a water depth of 348.3 m (Table T2 in the "Leg 194 Summary" chapter; Tables T1, T2). Piston coring advanced to 37.1 mbsf, where the carbonate platform was penetrated. The average recovery for the piston-cored interval was 100.8%.
Coring continued with the extended core barrel (XCB) system and advanced to 450.4 mbsf (Core 194-1193A-73X) with generally low recovery. Cores were retrieved at half-interval (~4.8 m) advances to maximize the chances of capturing the elusive reefal debris. The average recovery over this interval was 27.8%. Recovery was below 6% between 50 and 150 mbsf and improved in the interval from 150 to 180 mbsf, ranging between 10% and 60%, apparently as a result of higher amounts of mud in the formation.
Following the recovery of Core 194-1193A-73X, excessive backflow from the drill string resulted in the entire drill floor being sprayed with water. When the driller lowered the kelly into the drill pipe in preparation for making up the next connection, the drawworks mechanical brake did not hold. The driller applied the electric brake to gain control of the traveling assembly, but the assembly had already descended ~2 to 3 ft, thus bending the 20-ft and 30-ft knobbies along with the first joint of 5.5-in drill pipe in the rotary table. Apparently, the immediate cause of the incident was the wet mechanical brakes on the drawworks.
After the severely bent 30-ft knobby was laid out and the slightly bent 20-ft knobby was made up to the drill string, rotation and circulation could not be established. The string was worked with high pull, weight, and torque until rotation was regained. Mud sweeps were circulated to work the tight hole. The wireline was run to retrieve the latest core barrel, and the pipe was worked again until it eventually became free. The top drive and all traveling components were inspected for any damage, and no problems were detected. Coring operations resumed at 0730 hr on 16 January. The total operating time lost as a result of this incident was 7.75 hr.
XCB coring advanced from 450.0 to 515.0 mbsf with an average recovery of 17.2% for this interval. At this depth, hole instability prevented further coring. The pipe got stuck, and another 5 hr was needed to free it. After several wireline fishing trips failed to recover the last core barrel (Core 194-1193A-84X), the hole was displaced with 118 barrels (bbl) of mud, and the bottom-hole assembly (BHA) had to be recovered. The retrieved core barrel was found with a broken latch dog, which had jammed into the latch sleeve. The latter was cracked in several places.
During coring operations on 13 January, the rendezvous boat Black Samurai arrived from Mackay, Australia, with three scientists (Gilles Conesa, Gregor Eberli, and Wuchang Wei) and two ODP technicians (Austin Crawford and Gavin Eppard), who stayed on shore so that the Hydraulic Autoclave Coring Equipment (HYACE) engineers could be accommodated during the first 3 days. In addition to the HYACE team, the personnel leaving the JOIDES Resolution were Lamont-Doherty Earth Observatory representative Greg Meyers, ODP/Texas A&M University (TAMU) development engineer Eddie Wright, and ODP/TAMU technician Darren Lawrie.
While the drill string was being recovered, a helicopter from Reef Helicopters in Mackay landed on the vessel and removed roughneck Melchoir Pepito, who had been diagnosed with probable kidney stones. The helicopter landed at 1015 hr and departed with the patient at 1028 hr on 17 January.
The vessel was offset 20 m east of Hole 1193A. A rotary core barrel (RCB) BHA was lowered, and the seafloor was tagged, indicating a water depth of 348.3 mbsf. Hole 1193B was spudded at 1730 hr on 17 January. After the hole was washed ahead to 35.0 mbsf, rotary coring penetrated the hard cover of the carbonate platform and advanced 53.8 mbsf with 19% recovery. The average rate of penetration for the two cored intervals was 6.5 m/hr. A free-fall funnel (FFF) was deployed after the bit had been pulled back to 20.3 mbsf. The underwater television system was employed to verify that the FFF was visible and not buried in the top of the seafloor.
The pipe was tripped to make up the ADCB system (see "Sea Trials with the Advanced Diamond Core Barrel" in "Introduction" in the "Explanatory Notes" chapter) with a 7.25-in polycrystalline diamond compact (PDC) bit. The ADCB was deployed in anticipation of improved recovery of reefal limestone. The core barrels were dressed with the new Lexan liner and a combination basket/slip-type catcher. Hole 1193B was reentered with the ADCB (Fig. F3), and the bit was advanced to 53.8 mbsf, where coring was initiated. The first core (194-1193B-3Z) was cut in less than 7 min, with an advance of 4.7 m. The mud pump was set at 13 strokes/min, and the rotary speed was set at 40 rpm. The maximum weight on bit used throughout the core run was <3 kilopounds (kips) (average = ~2 kips). Operating pressure during the initial core run was between 300 and 350 psi. The second barrel gave a momentary indication that it landed, but immediately appeared to have lifted off of the seat as a result of a loss in operating pressure. The barrel was recovered and the core lifter case replaced with a standard slip-type catcher. The hole appeared to be packing off, so the pumps were turned up again before the barrel reached the bottom. Because of the softness of the material recovered in the first ADCB core, the decision was made to advance the core barrel, despite the fact that it appeared not to have landed properly. Core 194-1193B-4Z was cut in 15 min; the driller had a hard time keeping weight on the bit. After a 4.5-m core run, the sinker bars were deployed. The core barrel was jarred up by the wireline jar, but it would not come free. The pumps were turned up in an attempt to see if the barrel could be pushed down with pressure, which sheared off the shear pin in the overshot. Two more jarring attempts would not release the core barrel. The pipe was pulled again to retrieve the barrel, and it was found that the inner tube had collapsed, which distorted the diameter and prevented the section of the inner tube from being pulled through the landing ring. It appears that when the hole collapsed and pump pressures were increased momentarily between 2200 and 2400 psi, the path of least resistance was for the inner tube to collapse before clearing the annulus of the hole.
Hole 1193B was reentered with the ADCB at 0725 hr on 19 January. The bit was advanced to 63.2 mbsf, where ADCB coring was resumed. Total recovery over the interval from 53.8 to 91.0 mbsf yielded 16.4%, compared to 2.6% for the XCB over a similar interval. The bit appeared to have encountered a clay layer with Core 194-1193B-7Z, preventing any advance in 47 min of rotation, despite applying a weight of over 15 kips. The barrel was recovered, and the pump strokes were reduced in an attempt to clean the bit. Apparently, this corrected the problem because penetration and recovery improved on the next core. Drilling parameters were held constant over these cores, with bit weight averaging 5 kips, rotary speed at 40 rpm, and flow rate varying between 6 and 10 strokes/min (30 to 50 gal/min). The other significant difference was that 5 bbl of sepiolite mud was introduced in the pipe before breaking each connection to prevent backflow. After Core 194-1193B-4Z, no other hole problems were experienced.
After cutting Core 194-1193B-11Z, the inner barrel was dropped, but no indications were seen via pump pressure that the barrel had landed properly. Several more unsuccessful attempts were made to deploy the inner barrel. An improvised bit deplugger was run in an attempt to clear the core blockage. Several blows of the wireline jars were necessary to clear the throat. The core barrel subsequently landed correctly, but the low circulation pressure established earlier was lower by over 150 psi. Cores 194-1193B-12Z through 21Z were cut, but core recovery was very poor, and recovered cores were not cut to gauge but only captured by being jammed in the throat of the inner barrel. Average recovery for this portion of the hole dropped to 6.3% with many of the cores being recorded as zero despite the impression from the surface that the bit was encountering material that should have been recovered more easily. Most of the material appeared to be lost because the core was not being trimmed for the catchers. The driller also noted on several occasions that more than 1 m of fill (presumably lost core) was encountered on the bottom of the hole at the beginning of several coring attempts. Drilling parameters were the same for this interval as for the overlying interval that had better recovery.
At this point, the drill string was pulled, and it was found that ~50% of the cast matrix pilot portion of the bit that trims the core was missing. Jarring with the bit deplugger to clear the blockage in the throat had apparently broken it off. The bit looked brand new except for the broken core trimming portion and one lost PDC element. The PDC element was most likely lost from coming into contact with the broken portion of the bit that was lying in the hole after rotation and coring was reinitiated. A properly spaced out and designed bit deplugger is recommended to ensure that this will not occur again. Hole 1193B was officially terminated at 1515 hr on 20 January.
For the second time in 4 days, a medical evacuation by helicopter was required. At 1646 hr on 20 January, a Kawasaki helicopter from Reef Helicopters landed on the vessel. Melchoir Pepito, the roughneck with the kidney stones who was evacuated earlier, returned to the vessel ready for work. A scientist, Brooke Olson, was put on the helicopter in a stretcher, along with her belongings. She was diagnosed with a fractured femur. The helicopter left the vessel at 1657 hr. Olson's diagnosis was confirmed in the Mater Hospital, where she underwent surgery a couple of days later before returning home.
As the drilling crew made up the RCB BHA for Hole 1193C, the vessel was offset 20 m northeast of Hole 1193B. Hole 1193C was spudded at 1800 hr on 20 January, with the primary objective of serving as a dedicated logging hole. After drilling through the top pelagic section, the top of the carbonate platform was cored for the third time, from 35 to 70.1 mbsf, with an average recovery of 16.2%. A center bit was deployed, and continuous drilling advanced to 510 mbsf at an average penetration rate of 24 m/hr.
While drilling ahead with the center bit, the float valve is open to allow backflow at the rig floor while making connections. This is necessary because cuttings in the annulus create excess hydrostatic head in the pipe. To counteract the overpressure and ensure the annulus was being circulated clean, 10 bbl of sepiolite was introduced during each connection and then circulated while we drilled the next interval. While making a connection at 156.1 mbsf, the drill string became stuck. Circulation and rotation could only be reestablished after applying 40 kips of overpull and 700 A of rotary current. The string was worked up and down over a 20-m interval until normal torque and pressure values were established. A total of 340 bbl of sepiolite was circulated during this operation.
Four additional cores were taken from 510 to 548.5 mbsf, where basement was penetrated. Mud sweeps were pumped for each cored interval. A 50-bbl sepiolite sweep was circulated, the bit was released on bottom, and the hole was displaced with 172 bbl of sepiolite mud in preparation for logging. The recovery for this portion of the hole was 39.9%, with an average penetration rate of 24.4 m/hr. The total cored interval for Hole 1193C was 73.6 m, with 21.07 m recovered (28.6%). A total interval of 474.9 m was drilled without coring.
The drill string was pulled and had to be worked through a tight spot at 297 mbsf with 80 kips of overpull. After the drill string was freed, excessive backflow propelled mud from the open end of the drill pipe at the rig floor to the monkey board level with one stand of drill pipe pulled above the rotary table. The backflow quickly vented all of the mud from the drill pipe. The top drive was picked up at 297.2 mbsf, but circulation or rotation could not be established. A maximum of 200 kips of overpull was applied in a 3-hr attempt to free the pipe according to shallow-water guidelines. A 50-bbl sweep was pumped while we worked the tight hole. However, no indication was observed that the mud sweep was entering the annulus.
Severing operations commenced with a safety meeting for all personnel involved. The Schlumberger wireline was rigged up and all relevant safety checks were performed. Seventy-two pellets of 1.75-in Goex RDX were loaded for the severing charge. Depth of connection was 433.96 m of drill string length (75.06 mbsf). Prior to severing the drill pipe, the drill string compensator (DSC) was opened, and 30 kips of overpull was applied. The severing charge was fired, and no indication of free pipe was noted on the weight indicator. The DSC was overpressured to 70 kips, at which point the stuck pipe came free. Circulation and rotation were established. The wireline was retrieved and rigged down. The top drive was used to pull out of the hole, and the fragmented end of pipe was on deck by 2100 hr, ending operations at Site 1193.
As the drill string was being recovered, several attempts to retrieve the beacon failed.