LWD Sonic Waveform Data


ODP logging contractor: LDEO-BRG

Hole:  808I

Leg: 196

Location: Nankai Trough (NW Pacifc Ocean)

Latitude: 32° 21.2145' N

Longitude: 134° 56.7003' E

Logging date: May 22-27, 2001

Bottom felt: 4686 mbrf (used for depth shift to sea floor)

Total penetration: 1058 mbsf


TOOL USED: ISONIC (IDEAL Sonic-while drilling)

Remarks about the recording: none.


The original ISONIC data recorded during Logging-while-drilling operations have been translated into DLIS format by Schlumberger-Anadrill. 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 are then converted into ASCII and finally binary format.

Each row of the binary file s is composed of the entire waveform set recorded at each depth, preceded by the depth. 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: 3558 (5.08 cm sampling rate)

Number of rows: 1187 (15.24 cm sampling rate)


Any numerical software or programing language (matlab, python,...) can import the files for further analysis of the waveforms.


The following binary files are available at Hole 808I:


ISONIC from ISONIC/RAB/ADN (casing at 156 mbsf)

808I-2in.bin: 0-991 mbsf

808I-6in.bin: 0-991 mbsf


The binary files have been depth-shifted to the sea floor (-4686).


NOTE: For users interested in converting the data to a format more suitable for their own purpose, a simple routine to read the binary files would include a couple of basic steps (here in old fashioned fortran 77, but would be similar in matlab or other languages):

The first step is to extract the files dimensions and specification from the header, which is the first record in each file:

  open (1, file = *.bin,access = 'direct', recl = 50) <-- NB:50 is enough to real all fields

  read (1, rec = 1)nz, ns, nrec, ntool, mode, dz, scale, dt

  close (1)

The various fields in the header are:
      - number of depths
      - number of samples per waveform and per receiver
      - number of receivers
      - tool number (0 = DSI; 1 = SonicVISION; 2 = SonicScope; 3 = Sonic Scanner; 4 = XBAT; 5 = MCS; 6 = SDT; 7 = LSS; 8 = SST; 9 = BHC; 10 = QL40; 11 = 2PSA)
      - mode (1 = Lower Dipole, 2 = Upper Dipole, 3 = Stoneley, 4 = Monopole)
      - vertical sampling interval *
      - scaling factor for depth (1.0 = meters; 0.3048 = feet) *
      - waveform sampling rate in microseconds *

All those values are stored as 4 bytes integers, except for the ones marked by an asterisk, stored as 4 bytes IEEE floating point numbers.

Then, if the number of depths, samples per waveform/receiver, and receivers are nz, ns, and nrec, respectively, a command to open the file would be:

  open (1, file = *.bin, access = 'direct', recl = 4*(1 + nrec*ns))

Finally, a generic loop to read the data and store them in an array of dimension nrec × ns × nz would be:

  do k = 1, nz

    read (1, rec = 1+k) depth(k), ((data(i,j,k), j = 1,ns), i = 1,nrec)



For further information about the logs please contact:


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