LWD Sonic Waveform Data

IODP logging contractor: CDEX

Hole: C0006B

Expedition: 314

Location: Nankai Trough (NW Pacific Ocean)

Latitude: 33° 1.6350 '

Longitude: 136° 47.6390' E

Logging-while-drilling date: November 9, 2007

Sea floor depth (as seen on logs): 3899.5 mLRF

Total penetration: 885.5 mLSF (4785 mLRF)

TOOL USED: LWD sonicVISION

The original LWD sonic data have been translated into DLIS format by Schlumberger Drilling and Measurements. Each of the four waveforms consists of 151 samples at depth intervals of 15.24 cm (6 inches) and 5.08 cm (2 inches). The data in DLIS format is first loaded on a Sun system using GeoFrame software. The waveform data files, consisting of 4 waveforms each, are then converted into ASCII and finally binary format.

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: 18391 (5.08 cm sampling rate)

Number of rows: 6131 (15.24 cm sampling rate)

Each file can be viewed directly as an image with Spyglass transform or NIH image on MACs and PCs, or Fortner transform or Khoros on UNIX) - where it has to be opened as either 'raw' or 'binary matrix'. Any image or signal-processing package should also allow viewing it.

The following files have been loaded:

314-C0001D_2in.bin: 0-876.7572 mLSF

314-C0001D_6in.bin: 0-876.7572 mLSF

The binary files have been depth-shifted to the sea floor (- 3899.5 mLRF).

NOTE: 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 = 2*(1+nwav*nsamples))

where nwav is the number of waveforms (4) and nsamples the number of samples per waveforms (see above).

If the total number of depths where waveforms have been recorded is ndepth (for a 150 m interval with data every 15.24 cm, ndepth would be 1000), a generic loop to read the data would be

do k = 1, ndepth

...

read(1, rec=k) iz, (data(i), i = 1, nwav*nsamples)

z(k)=float(iz)/10

...

enddo

In such a case, the file dimensions will be ndepth rows by nwav*nsamples+1 columns

Additional information about the drilling and logging operations can be found in the Operations and Downhole Measurements sections of the expedition report, Proceedings of the Integrated Drilling Program, Expedition 314 . For further questions about the logs, please contact:

Yoshinori Sanada
IODP Department, CDEX
Japan Agency for Marine Science Technology(JAMSTEC)
3137-25, Showama-machi, Kanazawa-ku
Yokohama, 236-0001, Japan
tel: +81-45-778-5649

fax: +81-45-778-5704
e-mail: sanada@jamstec.go.jp

For any web site-related problem please contact:
E-mail: logdb@ldeo.columbia.edu