IODP Expedition 372

Creeping Gas Hydrate Slides and Hikurangi LWD

Daily Science Report for 4 January 2018

Location: Port of Lyttelton, New Zealand

Science Update: The vessel finished the 404 nmi transit to Lyttelton from Site U1517 and arrived at the pilot station at 0600 h. Expedition 372 ended at 0706 h with the first line ashore at the Port of Lyttelton.

Daily Science Report for 3 January 2018

Location: In transit to Lyttelton, New Zealand

Science Update: The laboratory teams spent the day finishing their site reports and methods chapters. The ship transited 252 nmi during the day and is scheduled to arrive at the pilot station in Lyttelton tomorrow at 0600 h.

Daily Science Report for 2 January 2018

Location:
• Hole U1517D (38°49.7765′S, 178°28.5604′E; water depth 720.9 mbsl)
• In transit to Lyttelton, New Zealand

Science Update: Three attempts were made to measure in situ formation pressure and temperature. The temperature dual-pressure tool (T2P) was deployed at 120 m. The deployment procedure went smoothly, but the Electrical Release System (ERS) could not latch back on to recover the tool, so we used the coring line. When the tool was recovered, the tapered probe was missing and the drive tube had been flooded. Data have yet to be recovered from the memory card due to a card error, but we will continue working to obtain the data. Following two unsuccessful T2P deployments, the hole was drilled down and the sediment temperature pressure tool (SETP) was deployed at 130 m. Tool deployment and recovery went smoothly; however, the data file was erased from the memory card. A final SETP deployment was made at 168.7 m after drilling the hole to that depth. After successful deployment and recovery, the data were downloaded from the tool. Upon converting the data from its native format to ASCII, it was noted the ASCII file had been corrupted. Efforts continue to convert the native data into a clean ASCII file.

Following the probe deployments the drill string was pulled out of the hole with the bit clearing the seafloor at 1030 h. At 1515 h operations on the rig floor were complete and the transit to to Lyttelton, New Zealand, started at 1536 h. We are scheduled to arrive at the Lyttelton pilot station at 0600 h on 4 January.

Daily Science Report for 1 January 2018

Location: Hole U1517D (38°49.7765′S, 178°28.5604′E; water depth 720.9 mbsl)

Science Update: After arriving at Site U1517, the bottom-hole assembly (BHA) was made up and the drill string assembled in preparation for formation temperature and pressure measurements. Hole U1517D began at 0720 h and was drilled down to 80 m. The center bit was retrieved and the temperature dual-pressure tool (T2P) deployed to make an in situ formation pressure measurement. The shear pins did not work on the first attempt and a second attempt was made ~1 h later. This time the tool was inserted into the sediment. The tool could not be recovered using the Electrical Release System (ERS) and had to be picked up using the coring winch. Upon retrieval, the T2P probe tip was damaged, having lost the thermistor in the tip; however, it did record a good pressure measurement. The center bit was installed and the hole drilled down to 120 m. After the center bit was retrieved, a second T2P probe was deployed at the end of the day.

Processed logging-while-drilling (LWD) files were received for Site U1519, and the LWD and log-seismic integration teams spent the day working on their reports and defining logging and seismic units for Sites U1518 and U1519. A science results meeting was held that summarized the findings of Sites U1518 and U1519.

Daily Science Report for 31 December 2017

Location:
• Hole U1520B (38°58.1587′S, 179°7.9233′E; water depth 3527.4 mbsl)
• Site U1517 (38°49.77′S, 178°28.56′E; water depth 720.9 mbsl)

Science Update: Logging while drilling (LWD) in Hole U1520B continued from 696.3 to 750.0 m. After reaching the total depth at 0430 h, the hole was cleaned with mud and the LWD tools and drill string were pulled from the hole. The bit cleared the seafloor at 0715 h. The LWD tools were broken down and the bit arrived back on the rig floor at 1930 h. At 1954 h the vessel began the 32 nmi voyage to back to Site U1517 where the plan is to conduct temperature dual-pressure tool (T2P) formation temperature and pressure measurements in Hole U1517D with possible pressure core sampler (PCS) coring if time permits. The ship arrived at Site U1517 at 2300 h.

The science laboratory teams are finalizing their Site U1517 reports and Methods chapters. The LWD team continues to work on the Site U1518 and U1519 reports.

Daily Science Report for 30 December 2017

Location: Hole U1520B (38°58.1587′S, 179°7.9233′E; water depth 3527.4 mbsl)

Science Update: Logging while drilling (LWD) continued in Hole U1520B from 236.3 to 696.3 m.

Initial results based on the real time LWD from Site U1520 show that the uppermost ~600 m of the sedimentary section is consistent with predominantly sandy and muddy layered sediments (probably turbidites). An upper sequence of soft sandy sediment overlies the Ruatoria avalanche deposit. These in turn overlie an apparently muddy sequence that becomes sandier with depth. Towards the base of the borehole the sediment appears more consolidated, with logging signatures indicating a change in lithology to higher velocity and denser material. The lower sequence is inferred to be predominantly pelagic sediments overlying the subducting Pacific Plate. The LWD science team continued to work on their reports for Sites U1518 and U1519.

Daily Science Report for 29 December 2017

Location: Hole U1520B (38°58.1587′S, 179°7.9233′E; water depth 3527.4 mbsl)

Science Update: Weather conditions improved throughout the morning and after 45.75 h spent waiting on weather, logging while drilling (LWD) in Hole U1520B began at 1345 h. By the end of the day, the hole was advanced to 236.3 m.

The LWD team continued work on the Site U1518 and U1519 logging results. Additionally, the LWD data from these sites are being tied to seismic profile sections. Real time monitoring of pressure in the borehole for safety is ongoing.

Daily Science Report for 28 December 2017

Location: Site U1520 (38°58.1640′S, 179°7.9350′E; water depth 3527.4 mbsl)

Science Update: The vessel spent the day waiting on weather as conditions continued to deteriorate throughout the day. Wind speeds, heave, and wave height peaking during the evening. The maximum recorded wind speed was 62 kt and the maximum heave was 7.7 m.

The logging-while-drilling (LWD) team continued to work on the Site U1518 and U1519 logs and the newly received processed data. They are having ongoing discussions about the logging interpretation around the thrust fault zone at Site U1518.

Daily Science Report for 27 December 2017

Location: Hole U1520A (38°58.1640′S, 179°7.9350′E; water depth 3527.4 mbsl)

Science Update: After a failed tool test, the logging-while-drilling (LWD) tools were pulled up to the vessel and the proVISION was replaced with the spare tool. The tools and drill string were set at 390 mbsl for a second LWD tool test. Again, the proVISION tool failed to send real time information. The tool string was deployed to the seafloor (3527.4 mbsl) and Hole U1520A began at 0845 h. The proVISION began sending real time data once the tools were turned on. The weather and sea conditions began to deteriorate and the drill string was pulled out of Hole U1520A after reaching a depth of 97.9 m. The bit cleared the seafloor at 1410 h and the vessel ended the day waiting on weather.

The initial logging results at Hole U1520A suggest that the 0–97.9 m interval is composed of turbidites. Resistivity images from Hole U1519A show borehole breakouts between 624–645 m that indicate the primary stress direction. The science laboratory teams submitted drafts of their Site U1517 reports for review.

Daily Science Report for 26 December 2017

Location:
Hole U1519A (38°43.6372′S, 178°36.8537′E; water depth 1004.1 mbsl)
Site U1520 (38°58.1640′S, 179°7.9350′E; water depth 3529.5 mbsl)

Science Update: Logging-while-drilling (LWD) operations at Hole U1519A continued from 623.7 to 650 m. Once total depth at the hole was reached, mud was pumped to clean out the hole. The LWD tools and the drill string were pulled out of the hole and the bit cleared the seafloor at 0425 h. At 0855 h the bit reached the rig floor and at 0930 h the vessel began the 28 nmi transit to Site U1520 (proposed Site HSM-05A). The ship reached Site U1520 at 1230 h, the LWD tools were assembled, and the drill string was run to a depth of 390 mbsl to test the tools. The proVISION tool was not sending real time data and the drill string was recovered so that the spare proVISION tool could be deployed.

The Downhole Measurements team continues to analyze the LWD results from Site U1518 and to discuss the depth at which the thrust fault is located. Site U1519 LWD data was received in the afternoon and is starting to be processed.

Daily Science Report for 25 December 2017

Location: Hole U1519A (38°43.6372′S, 178°36.8537′E; water depth 1004.1 mbsl)

Science Update: Logging-while-drilling (LWD) operations continued in Hole U1519A from 221.1 to 623.7 m. Below the thick, washed out zone from 140 to 235 m, borehole conditions improve and the log quality appears to be good.

The science laboratory teams are working on the reports for Sites U1517 and U1518. The logs from Hole U1518B clearly show the thrust fault zone, which is characterized by an increase in porosity and a decrease in velocity. Above the thrust fault (~319 m) there are indications that gas hydrates are present. The borehole images show bedding, fractures, and borehole breakouts.

Celebrations were held for the Christmas holiday that included a barbeque on the deck, a Christmas feast, and the Christmas program.

Daily Science Report for 24 December 2017

Location:
Hole U1518B (38°51.5476′S, 178°53.7621′E; water depth 2636.4 mbsl)
Hole U1519A (38°43.6372′S, 178°36.8537′E; water depth 1004.1 mbsl)

Science Update: The bit cleared the rotary table at 0100 h and the ship was secured for transit at 0257 h, ending Site U1518. The vessel arrived at Site U1519 (proposed Site HSM-01A) at 0530 h after a 15.4 nmi transit. The logging-while-drilling (LWD) bottom-hole assembly (BHA) was assembled and contained the geoVISION, SonicScope, NeoScope, TeleScope, proVISION, and StethoScope tools. The LWD tools and drill string were deployed to a depth of 952 mbsl and the tools were tested before starting the hole. Hole U1519A began at 1200 h and by midnight the hole was advanced to 221.1 m. Real time LWD data include the ultrasonic caliper, resistivity, gamma ray, porosity, annular pressure, nuclear magnetic resonance, and resistivity images. The annular pressure is being closely monitored for safety.

LWD data from Hole U1519A indicate good hole conditions from 0 to 140 m. From 140 to 235 m the hole is washed out and is inferred to be a sandy interval. A meeting was held to discuss results from Holes U1517A to U1517C.

Daily Science Report for 23 December 2017

Location: Hole U1518B (38°51.5476′S, 178°53.7621′E; water depth 2636.4 mbsl)

Science Update: Logging while drilling (LWD) in Hole U1517B continued from 372.2 to 600 m. After reaching total depth we circulated a mud sweep and pulled out of the hole. The bit cleared the seafloor at 1825 h. The remainder of the day was spent pulling up the drill string and breaking down the LWD tools.

The real time LWD data from Hole U1518B show a low density and low resistivity formation extending from ~300 to 430 m. This interval appears to have several washout intervals based upon the ultrasonic caliper readings. From ~430 to 600 m the resistivity and density values increase and the borehole conditions appear to be good.

Geochemical analyses from Hole U1517C are ongoing. Carbonate values from 0 to 150 m range between ~4% to 8%. Organic carbon content is less than 0.6% in this interval. The science laboratory teams are finalizing the site reports for Holes U1517A–U1517C and a pre-site meeting was held for Site U1519 (proposed Site HSM-01A).

Daily Science Report for 22 December 2017

Location: Hole U1518B (38°51.5476′S, 178°53.7621′E; water depth 2636.4 mbsl)

Science Update: Logging-while-drilling (LWD) operations continued in Hole U1518B to 372.7 m. After logging a portion of the thrust fault zone, the tools were pulled up to 334.7 m. Three pore pressure measurements were attempted using the StethoScope tool, all with poor results. The tools were then pulled up to 234.0 m to try three additional StethoScope measurements; these were unsuccessful as well. We lowered the tools back to the bottom of the hole, circulated a mud sweep to clean the hole, and ended the day preparing to advance the hole to a total depth of 600 mbsf.

Hole U1518B real time logging results show that from 0 to 300 m the formation has high density and resistivity. At ~300 m, the thrust fault was encountered and the density and resistivity drop over a 20 m interval. From 325 to 334.7 m, there is evidence of borehole washouts based on the caliper readings. Overall, the borehole conditions are good and the logs appear to be of high quality.

Moisture and density analyses are complete from Cores U1517C-27F to 36F. The porosity of the sediments from these cores is ~45%. Preliminary analyses of pore water samples from Hole U1517C yield gas hydrate saturation values (S_h) from 5% to 9% in five of the gas hydrate bearing samples, 10%–18% in two samples, and >50% saturation in three samples. Sample analysis for total organic and inorganic carbon is underway.

Daily Science Report for 21 December 2017

Location:
• Site U1518 (38°51.5367′S, 178°53.7603′E) waiting on weather
• Hole U1518B (38°51.5476′S, 178°53.7621′E; water depth 2636.4 mbsl)

Science Update: The first half of the day was spent waiting on weather and the ship was offset 20 m to the southeast of Hole U1518A. At 1310 h, an attempt was made to begin Hole U1518B; however, the sea conditions were too rough and prevented the start of the hole. After an additional 3 h of waiting on weather, Hole U1518B successfully began at 1600 h. As of midnight, the bit had reached 133 mbsf and real time logging-while-drilling (LWD) data was being observed by the science team. These real time data include the ultrasonic caliper, resistivity, gamma ray, porosity, annular pressure, nuclear magnetic resonance, and resistivity images.

Cores U1517C-29F to 36F (154.8–187.58 m) were split and described. These cores contain greenish-gray clayey silt and graded turbidite beds. The turbidites contain fine to medium sands. In Cores U1517C-35F and 36F (179.1–187.58 m) several cm-scale tephra layers are observed. Porosity of core samples averages ~50% in Cores U1517C-17H to 20F (90.6–118.49 m) then gradually declines to ~40% in Core U1517C-26F (144 m). The Chemistry Laboratory group is currently processing and running sediment and pore water samples. The LWD team is working on their Site U1517 chapter and are tying the LWD results to seismic reflection lines. Scientists are continually monitoring the real time LWD data from Hole U1518B for safety, to identify stations for pore pressure measurements using the StethoScope tool, and to observe LWD data quality.

Daily Science Report for 20 December 2017

Location:
• Hole U1518A (38°51.5368′S, 178°53.7606′E; water depth 2636.4 mbsl)
• Site U1518 (38°51.5367′S, 178°53.7603′E), waiting on weather

Science Update: The logging-while-drilling (LWD) tools and drill string were run to a depth of 2460 mbsl and the subsea camera was deployed to determine the depth of the seafloor. While the camera descended, 115 ft of drill line was cut off. The seafloor was tagged at 2636.4 mbsl. The camera was brought to the surface and the top drive installed. Hole U1518A began at 0855 h. Weather conditions and sea state deteriorated over the next few hours and the logging tools were pulled out of the hole at 1605 h, ending Hole U1518A. LWD data was collected from 0 to 117 m. The remainder of the day was spent waiting on weather.

Cores U1517C-18H to 28F (99.6–154.82 m) were split and described. The cores contain greenish gray clayey silt with sand and shell fragments in addition to graded turbidite beds. Some of the turbidite layers contain unconsolidated sand. Porosity varies between 40%–50% in the uppermost 90 m of core and a sharp increase in porosity occurs between 66–68 m. Pore water alkalinity has two maxima at ~17 and 70 m and the sulfate–methane transition zone is observed at 15 m. Chlorinity of the pore water indicates the presence of gas hydrates between ~135 to 165 m. The Downhole Measurements team continues to work with the LWD data and borehole images from Hole U1517A to construct logging units and initial interpretations. A fracture cluster is observed in the borehole image at ~55 m, which appears to lie close to the base of the landslide.

Daily Science Report for 19 December 2017

Location:
• Hole U1517C (38°49.7820′S, 178°28.5633′E; water depth 720.9 mbsl)
• Site U1518 (38°51.5367′S, 178°53.7603′E)

Science Update: Half-length APC (HLAPC) coring continued from Core U1517C-27F to 36F (145.9–188.5 m) with 72% recovery. The drill pipe was pulled out of the hole with the bit clearing the seafloor at 1015 h and the rotary table at 1220 h, ending Hole U1517C. A total of 177.8 m of core was recovered from the 188.5 m interval (94%). The ship was secured for the 20 nmi transit at 1310 h and arrived at Site U1518 at 1635 h. The logging-while-drilling (LWD) bottom-hole assembly (BHA) and drill pipe were run to a depth of 300 mbsl and the LWD tools were tested. After the test, we continued to assemble the drill string. The LWD tool string for Site U1518 contains the geoVISION, SonicScope, NeoScope, TeleScope, proVISION, and StethoScope tools.

Cores U1517C-19F to 36F (108.3–187.6 m) were scanned using the whole-round physical properties tracks, and Cores U1517C-5F to 17H (24.6–99.73 m) were split and described. These cores contain greenish gray thinly-bedded to laminated clayey silt, thick units of stacked turbidites composed of fine sand to silt, and massive clayey silt. Small cm-scale tephra layers as well as tephra blebs are observed. The cores also contain shell fragments and pyrite. Several samples for X-ray diffraction (XRD), carbonate content, total organic carbon, and moisture and density are being processed. Void space gas samples are being run through the gas chromatograph. Interstitial pore water results suggest the presence of gas hydrate in at least four samples based upon low chlorinity values.

Daily Science Report for 18 December 2017

Location:
• Hole U1517B (38°49.7820′S, 178°28.5633′E; water depth 720.2 mbsl)
• Hole U1517C (38°49.7820′S, 178°28.5633′E; water depth 720.9 mbsl)

Science Update: APC coring in Hole U1517B began at 0130 h. Core U1517B-1H was recovered full (9.4 m), so the decision was made to abandon Hole U1517B and attempt to recover a mudline core. The bit was raised 3 m and Hole U1517C began at 0210 h. Cores U1517C-1H and 2H penetrated to 15.2 mbsf before we switched to the half-length advanced piston corer (HLAPC) to recover a silt-rich interval. Cores U1517C-3F to 14F (15.2–71.6 m) were taken before switching back to the full-length APC for Cores U1517C-15H to 18H (71.6–108.3 m), all of which had partial strokes. The HLAPC was redeployed for Cores U1517C-19F to 26F. As of midnight, coring operations had penetrated to 145.9 m with 147.02 m of core recovered (101%). Several whole-round samples were taken on the core receiving platform that may contain gas hydrate based on temperature readings from infrared (IR) cameras. These samples will be used for shipboard interstitial water chemistry as well as postcruise research.

Cores U1517B-1H and U1517C-1H to 18H (0–108.3 mbsf) have been processed through the whole-round physical properties tracks and Cores U1517C-1H to 4F (0–24.6 m) were split and described. These cores contain dark greenish-gray silty clay and clayey silt with thin, cm-scale turbidite beds. Drilling disturbance, in particular arching structures from the piston coring, is present throughout the cores. There are occasional flecks of tephra and foraminifers as well as shell fragments.

Methane concentrations are low in Cores U1517B-1H and U1517C-1H to 2H. From Cores U1517C-3F to 36F (15.2–188.5 m) the methane concentrations vary between 2000 to 5000 ppm, with a maximum value of 10,500 ppm in Section U1517C-4F-4 (24 m). A total of 54 samples were collected from Hole U1517C for interstitial pore water chemistry, which are currently being processed in the laboratory.

Logging-while-drilling results from Hole U1517A are in the process of being analyzed. These data are being used to identify distinct logging units. The image logs have been processed and bedding features and fractures are being identified. Resistivity, density, sonic velocity, and resistivity images were used to make predictions on the presence or absence of gas hydrates at certain intervals in the core. The Downhole Measurements team is working on the Site U1517 report and filling in their logging templates.

Daily Science Report for 17 December 2017

Location: Hole U1517A (38°49.7722′S, 178°28.5574′E; water depth 725.3 mbsl)

Science Update: Logging while drilling (LWD) in Hole U1517A continued through the first half of the day, reaching the total depth of 205 mbsf at 1115 h. After a mud sweep, the drill pipe and LWD bottom-hole assembly (BHA) was pulled from the hole, with the logging tools recording sonic measurements on the way up. The bit cleared the seafloor at 1245 h and the rotary table at 1840 h, ending Hole U1517A. The vessel was offset 20 m to the southeast for coring operations in Hole U1517B. The day ended with the advanced piston corer (APC)/extended core barrel (XCB) BHA and the drill string assembled to a depth of 715 mbsl.

The Downhole Measurements scientists observed the LWD data in real time and made initial interpretations about the presence of gas hydrate in selected intervals.

Daily Science Report for 16 December 2017

Location:
In transit to Site U1517 (proposed Site TLC-04B)
Hole U1517A (38°49.7722′S, 178°28.5574′E; water depth 725.3 mbsl)

Science Update: The 3407 nmi transit to Site U1517 ended at 0200 h. The thrusters were lowered and the ship moved to the site coordinates at 0247 h. The advanced piston corer (APC)/extended core barrel (XCB) bottom-hole assembly (BHA) was put together in preparation for Hole U1517B. The logging-while-drilling (LWD) tool string was assembled and contained the geoVISION, SonicScope, NeoScope, TeleScope, and proVISION tools. The LWD tools and drill string were run to 672 mbsl and the subsea video camera was deployed to observe the drill bit tag the seafloor, which occurred at 1755 h. The seafloor depth for Hole U1517A is 725.3 mbsl. The camera system was retrieved and Hole U1517A was spudded at 1935 h. As of midnight, the bit had advanced 63 mbsf.

The Downhole Measurements scientists began observing the LWD data in real time. This included the borehole caliper, resistivity at bit, annular pressure, gamma ray, velocity, porosity, bulk density, and nuclear magnetic resonance.