Temperature Data Processing
ODP logging contractor: LDEO-BRG
Hole: 1189B
Leg: 193
Location: Manus Basin (Bismarck Sea)
Latitude: 3° 43.236' S
Longitude: 151° 40.506' E
Logging date: December 25-26, 2000
Bottom felt: 1693 mbrf
Total penetration: 206 mbsf
Total core recovered: 13.7 m (7.8 %)
Temperature Tool Used: HTGC
Water depth: 1692 mbrf
Logging Runs
Logging string 1: HTGC (one main and one repeat pass)
Logging string 2: DIT/HLDS/APS/HNGS/HTGC (main and repeat pass)
Logging string 3: FMS/GPIT/NGT/DSI/HTGC (2 passes)
The wireline heave compensator was used to counter ship heave.
HTGC (main pass): Bottom-hole assembly at 26 mbsf
DIT/HLDS/APS/HNGS/HTGC (main pass): Bottom-hole assembly at 26 mbsf
FMS/GPIT/NGT/DSI/HTGC (pass 1): Bottom-hole assembly at 26 mbsf
FMS/GPIT/NGT/DSI/HTGC (pass 2): recorded open-hole
Casing at 34 mbsf.
The HTGC (High-pressure, high-temperature telemetry gamma-ray cartridge) consists of a gamma-ray detector made of a NaI crystal, a photo multiplier tube, a high-voltage generation circuit, and a preamplifier of the gamma-ray pulse all built in one package. The number of the output pulses from the detector is counted at a rate of 8 Hz, and the count is sent up-hole. Housed in a heatsink and dewar flask that allow operations in high-temperature environments (260°C), this tool also has a 31-pin upper and lower head asset and is combinable with any standard 3.375-in tool without additional adaptors. The data acquisition software cannot distinguish between the tools, but the HTGC has the correct length and measure point and gamma-ray response for the flasked tool.
The gamma-ray values are measured in American Petroleum Institute (API) units. These units are derived from the primary Schlumberger calibration test facility in Houston, Texas, where a calibration standard is used to normalize each tool. Because the natural gamma-ray response is sensitive to borehole diameter and the weight and concentration of bentonite or potassium chloride present in the drilling mud, corrections are routinely made for these effects during data processing at LDEO-BRG. The HTGC also has an external sensor that allows for real time temperature measurements of the borehole fluids. This sensor was located on the cable head that was used on top of each tool string. Two thermocouples were used to calibrate the cable head temperature measurements. At 0°C there is a -1.1°C difference between the calibration standard and the cable head measurements. At 106°C there is a 1.7°C difference.
Processing
No processing of the HTGC temperature data was performed. The temperature measurements made on the cable head are rough indicators of borehole conditions because there are post-drilling disturbances and some fluid displacement effects from the entire tool string that can affect the temperature measurements especially in the down logs. The temperature data have been depth shifted to match the other logs by using the gamma ray measurement recorded with temperature.