Temperature Data Processing
IODP-USIO logging contractor: LDEO-BRG
Location: Cascadia Margin (NE Pacific)
Latitude: 48° 47.3617' N
Longitude: 126° 40.7159' W
Logging date: September 30, 2005
Sea floor depth (drillers'): 957.4 mbrf
Sea floor depth (loggers'): 956 mbrf
Total penetration: 211 mbsf
Total core recovered: 1.03 m (1.0.8 % of cored section. Note that this was a hole drilled for logging; only 9.5 m were cored at the bottom of the hole)
Oldest sediment cored: Late Miocene
Temperature Tool Used: LDEO-TAP
Depth versus time recording available: NO
Logging string: DIT/APS/HLDS/HNGS/TAP
The TAP tool acquires borehole temperature, tool acceleration, and hydrostatic pressure. It may be run in either memory mode, where the tool is fastened to the bottom of logging string and data is stored in the on-board memory, or in telemetry mode, where the tool is run alone and data is recorded in real-time by the third-party data acquisition system. When the tool is run in memory mode, the stored data is dumped to the third party data acquisition system upon the tool's return to the rig floor.
Borehole fluid temperature is recorded with one thermistor located at the bottom of the tool. The internal temperature of the tool is recorded as well. A pressure transducer is included to turn the tool on and off at specified depths when used in memory mode. Typically, data acquisition is programmed to begin 100 m above the seafloor. A 3-axis accelerometer is also included to measure tool movement down hole. These data are expected to be instrumental in analyzing the effects of heave on a deployed tool string which will lead to the fine tuning of the WHC (wireline heave compensator).
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.
During this leg no depth versus time data was recorded. A linear relationship of pressure versus depth has been calculated from the pressure reading at the mudline and at the total logging depth. The pressure at the mudline corresponds to the pressure recorded by the tool during the calibration stop (about 5 minutes), which takes place at the mudline on each logging run. The pressure readings are then converted to depth using a pressure/depth conversion that is linearly interpolated between the values determined at the mudline and total logging depth.
total depth (TD)= 210 mbsf
pressure at mudline (Pml)= 1415 psi
pressure at total depth (Ptd)= 1784 psi
Information about the temperature logging operations can be found in the Site Chapter, IODP Initial Reports Expedition 311.
For further information about the processing, please contact:
E-mail: Gilles Guerin
E-mail: Cristina Broglia