Temperature Data Processing
Wireline Standard Data Processing
ODP Logging Contractor: LDEO-BRG
Location: Eratosthenes Sea Mount (Eastern Mediterranean)
Latitude: 34° 4.104' N
Longitude: 32° 43.524' E
Logging Date: April, 1995
Bottom Felt: 2564 mbrf (used for depth shift to sea floor)
Total Penetration: 600.3 mbsf
Total Core Recovered: 72.3 m (14 %)
Temperature Tool Used: LDEO-TLT
Depth versus time recording available: NO
Logging string 1: ACT/GST/NGT
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 Leg 160 depth versus time data were collected at Holes 966F, 968A, and 970A only.
A linear relationship of pressure versus depth has been calculated from the pressure reading at the mudline. 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.
Depth = Pressure * x - WD
Depth = mbsf
Pressure = bars
x = pressure conversion coefficient (m/bars)
WD = water depth, mbrf
This procedure does not fully account for the vagaries of the pressure readings that result in lots of ups and downs in the generated depth channel. Further problems arise because of pumping during logging operations, which affects the pressure, especially when the Side Entry Sub is used. Also, whenever heavy pills of mud are used, the pressure-depth calculation is affected, resulting in a non-linear effect that is difficult to account for. If the pressure conversion coefficient is recalculated for the mudline, the resultant total depth is often wrong.
The following processing has been performed at Hole 967E:
Logging Run: ACT/GST/NGT
Mudline P=265.65 bars
Pressure conversion factor calculated from pressure at mudline
Depth = Pressure * 9.6512-2564
Information about the temperature logging operations can be found in the Site Chapter (Operations, Downhole Measurements, and Heat Flow sections), ODP IR volume 160.
For further information about the processing, please contact:
E-mail: Cristina Broglia