Wireline Sonic Waveform Data

ODP logging contractor: LDEO-BRG

Hole: 1186A

Leg: 192

Location: Ontong-Java Plateau (tropical NW Pacific Ocean)

Latitude: 0° 40.7873' S

Longitude: 159° 50.6519' E

Logging date: October 27-28, 2000

Bottom felt: 2740 mbrf

Total penetration: 1034 mbsf

Total core recovered: 88.6 m (26.32 %)

TOOL USED: DSI (Dipole Sonic Imager)

Recording mode: Monopole P&S and Lower Dipole mode.

Remarks about the recording: none.

MONOPOLE P&S MODE: measures compressional and hard-rock shear slowness. The monopole transmitter is excited by a high-frequency pulse, which reproduces conditions similar to previous sonic tools.

LOWER DIPOLE MODE: measures shear wave slowness using firings of the lower dipole transmitter.

As most Schlumberger logs, acoustic data are recorded in DLIS format. Each of the eight waveforms consists of 512 samples, each recorded every 10 (monopole P&S) and 40 microsec (dipole modes), at depth intervals of 15.24 cm (6 inches). The original data in DLIS format is first loaded on a Sun system using GeoFrame software. The packed waveform data files are then converted into ASCII and finally binary format.

Each row of the binary file is composed of the entire waveform set recorded at each depth, preceded by the depth. In the case of 8 waveforms with 512 samples per waveform, this corresponds to 1 + 4x512 = 4097 columns. In this hole, the specifications of the files are:

Number of columns: 4097

Number of rows: 2101 (Pass 1)

Number of rows: 2081 (Pass 2)

Number of rows: 211 (Pass 3)

All values are stored as ' IEEE floating point numbers' (= 4 bytes).

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

The following files were converted:

DSI from FMS/DSI/GPIT/NGT (Pass 1, recorded open-hole)

1186A-mono_p1.bin: 3433-3750 mbrf

DSI from FMS/DSI/GPIT/NGT (Pass 2: recorded open-hole)

1186A-mono_p2.bin: 3430-3770 mbrf

1186A-ldip_p2.bin: 3430-3770 mbrf

DSI from FMS/DSI/GPIT/NGT (Pass 3, recorded open-hole)

1186A-mono_p3.bin: 3718-3750 mbrf

1186A-ldip_p3.bin: 3718-3750 mbrf

NOTE: the DSI runs labeled as #1 and 3 have been actually switched. The shorter one was the first one to be recorded; it aborted after recording less than 50 meters in the basement section.

The sonic waveform files are not depth-shifted to a reference run or to the seafloor. For depth shift to the sea floor, please refer to the DEPTH SHIFT section in the standard log documentation file.

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)

  enddo

For further information about the logs please contact:

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