Temperature (CBTT) Data Processing


ODP logging contractor: LDEO-BRG

Hole: 1188A

Leg: 193

Location: Manus Basin (Bismarck Sea)

Latitude:  3°43.698' S

Longitude: 151°40.200' E

Logging date: November 25, 2000

Bottom felt: 1653 mbrf (by LWD gamma ray)

Total penetration: 72 mbsf

Total core recovered: n/a (LWD hole)

Temperature Tool Used: CBTT
Top Depth: 28 mbsf
Bottom Depth: 33 mbsf
Temperature versus time recording available: Yes


The Core Barrel Temperature Tool (CBTT) was developed by the Borehole Research Group of the Lamont-Doherty Earth Observatory (LDEO) for assessing temperature conditions while drilling and determining if the conditions were favorable for subsequent LWD operations in hydrothermal environments. Similar to the drill string accelerometer (DSA), the CBTT is another step in series of measurements while coring that has been used in the past to characterize in situ drilling conditions. The primary purpose of the CBTT was to measure and record the borehole temperatures while drilling. These measurements could then be correlated to pump rates used during coring operations in order to determine the feasibility of performing LWD operations in the high temperature conditions that were encountered in the Manus Basin. The CBTT contains a thermocouple and a battery operated electronics board encased in a single dewar inside the pressure case that was designed for the DSA.

During Leg 193, the preliminary plan was to use the CBTT in every other core barrel at Sites 1188, 1189, and 1190. The CBTT would be deployed on an RCB core barrel for a mudline measurement and then on every other RCB core barrel run. On each run, the CBTT would begin data acquisition at a pre-determined depth as programmed by the logging scientists. For ease of deployment, the CBTT was designed as a removable extension of the RCB core barrel. Using standard threaded connections, the CBTT was attached to the top of the core barrel by a Core Tech prior to the core barrel deployment. Except for the connection and disconnection of the CBTT, coring activities were not be affected by its presence. Upon CBTT/core barrel retrieval, the CBTT was disconnected and the data downloaded to the third party data acquisition system in the Downhole Measurements Laboratory for immediate analysis. The data was then correlated to pumping rates to determine the necessary parameters for successful subsequent LWD operation in the 1188, 1189, and 1190 sites.

The temperature vs. time record from Core 193-1188A-4R shows profiles for both the internal (Tint) and external (Text) temperature sensors. The time of initialization, a period of ~6 min where Text was disconnected, a heating up period when the tool was at the rigfloor, a cooling trend as the core barrel was released from the rigfloor, and finally, the bottom hole profile were all recorded. Text shows an average bottom hole temperature of 3.9 ± 0.4ºC whereas Tint shows an average temperature of 28.2 ± 0.8°C. These measurements imply either effective cooling of the borehole through pumping an average of 50 strokes per minute (spm), which is ~250 gal/min, or very cool shallow conditions for this area. The tool was programmed for a 1 s sampling rate.

The tool was disassembled and cleaned thoroughly after retrieval. Several checks were made to determine the erratic behavior in data recording times and communication. In the mean time, the DSA/CBTT pressure case was deployed in Sites 1189 and 1191 with maximum temperature thermometers to provide an idea of downhole temperature conditions while troubleshooting with the CBTT electronics continued. The maximum temperature measurements recorded with the thermometers showed that the conditions were favorable for attempting a 75-m LWD hole in Site 1189. The same reasoning was used for the Satanic Mills area (Site 1191). Unfortunately, the bit, core barrel, and DSA pressure case were lost at this site effectively ending any other potential deployment of the CBTT during Leg 193.

For additional information contact:

Cristina Broglia
Phone: 845-365-8343
Fax: 845-365-3182
E-mail: Cristina Broglia