Temperature (UHT-MSM) Data Processing
ODP logging contractor: LDEO-BRG
Location: Manus Basin (Bismarck Sea)
Latitude: 3°43.698' S
Longitude: 151°40.200' E
Logging date: November 25, 2000
Bottom felt: 1653 mbrf (by LWD gamma ray)
Total penetration: 72 mbsf
Total core recovered: n/a (LWD hole)
Temperature Tool Used: UHT-MSM
Depth versus time recording available: YES
One pass recorded. Data recorded both downhole and uphole. No wireline heave compensation was used for this run.
The ultra-high temperature multisensor memory tool (UHT-MSM) is a slimhole probe running on the coring line (sand line). The Geophysical Research Corporation developed the tool for the University of Miami and it was deployed for the first time during ODP Leg 169. The UHT-MSM contains internal and ultra-high external temperature measuring devices, a pressure gauge, a multisensor memory unit, and a dewar flask that acts as an insulator to maintain a stable temperature and cool-down rate for the tool. The heat shield is aircraft-grade aluminum bound at both ends by brass heat sinks. The dewar flask can maintain an internal temperature suitable for tool operation for 4 - 5 hr at an external temperature of 400¹C. Operations are possible up to 10 hr if the average temperature does not exceed 232¹C.
The UHT-MSM tool records pressure, borehole fluid temperature (Text), and internal tool temperature (Tint). This tool can only be run in memory mode, where the tool is fastened to the sand line and the data is stored in memory and downloaded upon retrieval. Borehole fluid temperature is recorded with one thermistor located at the bottom of the tool. A pressure transducer is programmed to turn the tool on at a depth specified by the operator, which is typically set to begin 30 min after tool initialization.
Drilling and circulation operations considerably disturb the temperature distribution inside the borehole, thus preventing equilibrated temperature conditions. The amount of time elapsed between the end of drilling fluid circulation and the beginning of logging operations is not long enough to allow the borehole to recover thermally.
To obtain depth records, the internal tool clock was synchronized with rig floor time and the computer in the subsea shop onboard the JOIDES Resolution. The computer in the subsea shop was then used to obtain cable length time-depth records of the sand line as the tool was being lowered in the hole. These depth data were merged with the data recorded in memory by the UHT-MSM tool by matching absolute time in the two data sets. The sub-sea shop measured depth at 4 to 5 sec intervals whereas the tool measured temperature at 1-sec intervals. Therefore, depth values were interpolated from the toolÍs temperature versus depth profile. The depth values provided in the processed files are reported in meters below rig floor (mbrf) and meters below sea floor (mbsf). The pressure data was not included in this file because the pressure transducer was not working properly. The temperature profiles are given with a starting and ending depth of 20 meters above sea floor.
This hole was re-entered approximately 26 days after it was initially drilled. Shortly after re-entry, the bottom of the drill pipe encountered a restriction at 3-mbsf and the UHT MSM penetrated to a logging total depth (TD) of 7 mbsf. Several attempts to pass through the obstruction failed and a 15-min temperature station was recorded before the tool was retrieved. Because of the attempts to pass through the obstruction, the best way to visualize these data is to plot the profiles versus time.
Information about the temperature logging operations can be found in the Site Chapter (Explanatory Notes, Operations, and Downhole Measurements sections), ODP IR volume.
For further information about the processing, please contact:
E-mail: Cristina Broglia