LWD Sonic Waveform Data
IODP drilling and logging operator: CDEX
Hole: C0002F
Expedition: 338
Location: Nankai Trough (NW Pacific Ocean)
Latitude: 33° 18.0507' N
Longitude: 136° 38.2029' E
Logging-while-drilling date: November 2-13, 2012
Total
penetration: 3973 m LRF (2005.5 m LSF)
TOOL USED: sonicVISION
The original LWD
sonic data have been unpacked by Schlumberger Drilling and
Measurements using GeoFrame's Preprocessor module, which also applies a gain correction. At LDEO-BRG the four waveforms have first been converted into ASCII and then binary format.
Each of the four waveforms consists of 151 samples at depth
intervals of 15.24 cm (6 inches). Each line of the
binary files is composed of the entire waveform set recorded at each depth,
preceded by the depth (multiplied by 10 to be stored as an integer). In the
case of 4 waveforms with 151 samples per waveform, this corresponds to 1 +
4x151 = 605 columns. In this hole, the specifications of the files are:
Number of columns:
605
Number of
rows: 7629 (15.24 cm sampling
rate)
The following
files have been loaded:
338-C0002F_6in.bin: 847.0392-2009.5464 m LSF
The binary files
are depth-shifted to the sea floor (- 1967.5 m).
For users interested in reading and
converting the data to a format more suitable for their own purpose, the
fortran declaration used to open the file *.bin would be:
open (1, file = *.bin,access = 'direct', recl = 4*(1+nrec*nsamples))
where nrec is the number of receivers (8 in the case of the DSI) and nsamples the number of samples per waveforms.
If the total number of depths where waveforms were recorded is ndepth (for a 150 m interval with data every 15cm, ndepth would be 1001), a generic loop to read the data would be
do k = 1, ndepth
...
read(1, rec=1+k) depth(k), ((data(i,j,k), j=1,nsamples),i = 1,nrec))
...
enddo
the first record in each file is a header with some of the file specifications:
- number of depths
- number of samples /trace
- number of receivers
- tool number = 2 (sonicVISION / MP3)
- vertical sampling interval
- scaling factor for depth
- waveform sampling rate in microseconds
Additional information about the drilling and logging
operations can be found in the Operations and Downhole Measurements sections of
the expedition reports, Proceedings of the Integrated Drilling Program, Expedition 338. For further questions about the online database please contact:
Phone: 845-365-8343
Fax: 845-365-3182
E-mail: Cristina Broglia
For questions about the processing of the resistivity images please contract:
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
Email: ykido@jamstec.go.jp
Yuichi Shinmoto
Email:shinmoto@jamstec.go.jp