Temperature Data Processing
ODP logging contractor: LDEO-BRG
Hole: 808C
Leg: 131
Location: Nankai Trough (NW Pacific Ocean)
Latitude: 32° 21.17' N
Longitude: 134° 56.66' E
Logging date: April, 1990
Bottom felt: 4685.5 mbrf (used for depth shift to sea floor)
Total penetration: 1327 mbsf
Total core recovered: 572.4 m (55 %)
Water Depth: 4674.6 mbsl
Temperature Tool Used: LDEO-TLT
Depth versus time recording available: NO
Logging Runs
Logging string: DIT/BHC/NGT
Wireline heave compensator was not used because the sea was calm.
The LDEO-TLT tool is a self-contained, high precision, low-temperature logging tool that is attached to the bottom of the Schlumberger tool strings. The tool provides two temperature measurements (in degree Celsius, recorded by a fast-response and a slow-response thermistor. The fast-response thermistor, though low in accuracy, is able to detect sudden, small temperature excursions caused by fluid flow between the formation and the borehole. The highly accurate, slow-response thermistor can be used to estimate heat flow. Pressure and the two temperature measurements are recorded as a function of time: conversion to depth can be based on the pressure reading (Legs 123-157) or, preferably, on simultaneous recording (by Schlumberger) of depth and time (Legs 159-181).
The data was recorded through drill pipe from 0 to 770 mbsf. A pressure-depth relationship was originally used to calculate depth, but no documentation is available about the actual calculation. As no original data was available at the time of this review, no re-processing could be performed. The calculated depths were smoothed with a 50-samples running average. Temperatures were smoothed with a 5-samples window.
Information about the temperature logging operations can be found in the Site Chapter (Operations, Downhole Measurements, and Heat Flow sections), ODP IR volume 131.