Chevron Gulf of Mexico Gas Hydrate JIP Drilling Program

Wireline Sonic Waveform Data

JIP drilling contractor: Chevron

JIP logging contractor: Schlumberger

Hole: KC151-3

Expedition: 1

Location: Keathley Canyon (Gulf of Mexico)

Latitude: 26° 49' 22.68" N (NAD27)

Longitude: 92° 59' 11.94" W (NAD27)

Sea floor depth (step in GR log): 1335 mbrf
Sea floor depth (drillers'): 1333.6 mbrf
Total penetration: 444.1 mbsf

TOOL USED: DSI (Dipole Sonic Imager)

Recording mode: Monopole P&S and Cross-Dipole modes.

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.

CROSS-DIPOLE MODE: uses alternate firings of upper and lower dipole transmitter, thus allowing acquisition of orthogonally polarized data for anisotropy studies.

Acoustic data are recorded in DLIS format. Each of the eight waveforms generally consists of 512 samples (256 in cross-dipole mode), each recorded every 10 (monopole P&S) and 40 microsec (all dipole and Stoneley 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 line 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 general 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: 1938 (downlog)
Number of rows: 2313 (uplog)

All values are stored as 'signed short integers' (= 16 bits signed).

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:
DSI from DSI/GPIT/NGT (downlog, BHA at 1456 mbrf)
KC151-3_mono_d.bin: 1383.18-1678.38 mbrf
KC151-3_cd_udip_il_d.bin: 1383.18-1678.38 mbrf
KC151-3_cd_udip_cl_d.bin: 1383.18-1678.38 mbrf
KC151-3_cd_ldip_il_d.bin: 1383.18-1678.38 mbrf
KC151-3_cd_ldip_cl_d.bin: 1383.18-1678.38 mbrf

DSI from FMS/DSI/GPIT/SGT (uplog, BHA at 1455 mbrf)
KC151-3_mono_up.bin: 1324.05-1676.4 mbrf
KC151-3_cd_udip_il_up.bin: 1324.05-1676.4 mbrf
KC151-3_cd_udip_cl_up.bin: 1324.05-1676.4 mbrf
KC151-3_cd_ldip_il_up.bin: 1324.05-1676.4 mbrf
KC151-3_cd_ldip_cl_up.bin: 1324.05-1676.4 mbrf

All values are stored as '32 bits IEEE float'.

Any image or signal-processing program should allow to import the files and display the data.

The sonic waveform files are depth-shifted to the seafloor (- 1335 m) but are not depth-matched to the reference run.

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

Additional information about the drilling operations can be found in the cruise report. For further questions about the logs, please contact:

Cristina Broglia

Phone: 845-365-8343

Fax: 845-365-3182

E-mail: Cristina Broglia