Logging-While-Drilling
Data Processing
Coring and logging operator: CDEX
Hole: C0022A
Expedition: 338
Location: Nankai Trough (NW Pacific Ocean)
Latitude: 33° 13.068' N
Longitude: 136° 43.454' E
Logging-while-drilling date: December 28-29, 2012
Sea floor depth (as seen on logs): 2704 m LRF
Total penetration: 3124.5 m LRF (420.5 m LSF)
The
downhole logs were recorded using the LWD/MWD
(Logging-While-Drilling/Measurement-While-Drilling) system, which employs
instruments that are part of the drill string itself. The advantages of this
technique include being able to log in formations that would not provide a
stable hole for wireline logging (e.g. the upper section of sedimentary
formations) and logging a hole immediately during drilling, so that it is in
good condition and largely free of wash-outs. The data is recorded in the
tool's memory and downloaded when the drill string returns to the rig floor. A
small subset of the data is transmitted up to the ship during drilling.
The
following services were employed in Hole C0022A :
geoVISION-8 / arcVISION-8 / TeleScope (resistivity, resistivity images, velocity and gamma ray, azimuth, annulus fluid temperature and pressure)
The rate of penetration ranges from 20 to about 45 m/hr.
Depth
shift: The original logs
have been depth shifted to the sea floor (- 3113 m) by JAMSTEC personnel.
Resistivity data: The geoVISION resistivity is sampled with a 0.03048 m (1.2 in) sampling rate. According to the header of the printouts produced by Schlumberger, the resisistivity has been corrected for bit size and mud resistivity.
Quality Control
During the processing, quality control of the data is performed by inter-comparison of all logging data to ensure that reasonable values are returned for expected lithology types and features on the logs reflect true formation characteristics and are not artifacts. The overall quality of the logging data is good.
Additional information about the drilling and logging operations can be found in the Operations and Logging-while-drilling sections of the expedition report, Proceedings of the Integrated Drilling Program, Expedition 338.
For questions about the online database, please contact:
Cristina Broglia
Phone: 845-365-8343
Fax: 845-365-3182
E-mail: Cristina Broglia
For questions about the procesing of the resistivity images, please contact:
Tanzhuo Liu
Phone: 845-365-8630
Fax: 845-365-3182
E-mail: Tanzhuo Liu
For questions about the logs, please contact:
Yoshinori Sanada
E-mail: sanada@jamstec.go.jp
Yukari Kido
E-mail: ykido@jamstec.go.jp
Yuichi Shinmoto
E-mail: shinmoto@jamstec.go.jp