Temperature Data Processing
ODP logging contractor: LDEO-BRG
Location: Walvis Ridge (tropical SE Atlantic)
Latitude: 19° 37.1818' S
Longitude: 11° 19.1598' E
Logging date: September, 1997
Bottom felt: 805.5 mbrf
Total penetration: 452.7 m
Total core recovered: 393.5 m (91.4 %)
Water Depth: 804 mbrf
Temperature Tool Used: LDEO-TLT
Depth versus time recording available: YES
Logging string 1: DIT/SDT/NGT
Logging string 2: APS/HLDS/HNGS
Wireline heave compensator was used to counter ship heave.
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).
During this leg depth versus time data was recorded on a personal computer (part of the L-DEO digital logging data acquisition system in the ODP Downhole Measurements Laboratory aboard the JOIDES Resolution) with input from the Schlumberger MAXIS computer. The depths recorded through this system are the same used by Schlumberger to measure cable length as recorded in the logging data files. These depth data were merged with the data recorded in memory by the Temperature Logging Tool (TLT) by matching absolute time in the two data sets. Time versus depth data from the MAXIS was available during logging at all holes. The depths in the processed files are reported in meters below sea floor (mbsf). At each hole, the constant depth shift applied to the original temperature logs was the same as that applied to all of the other logs; it is given in meters below rig floor (mbrf) in the header of the processed files.
Information about the temperature logging operations can be found in the Site Chapter (Operations, Downhole Measurements, and Heat Flow sections), ODP IR volume 175.
For further information about the processing, please contact:
E-mail: Cristina Broglia