Chevron Gulf of Mexico Gas Hydrate JIP Drilling Program
LWD Sonic Waveforms
Drilling contractor: Chevron
Logging contractor: Schlumberger
Hole: AC21-B
Expedition: JIP2
Location:
Latitude: 26° 56' 39.1900" N
Longitude: 94° 53' 35.6216" W
Sea floor depth (step in GR log): 4934 ftbrf
Sea floor depth (drillers'): 4934 ftbrf
Total penetration: 6050 ftbrf
TOOL USED: sonicVISION
Remarks about
the recording: none.
Acoustic
data were recorded by Schlumberger in DLIS format. Each of the four waveforms
consists of 151 samples, at depth
intervals of 2 and 6 inches. The original 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
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 general 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: (2-in data)
Number of rows: (6-in data)
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:
AC21-B_2in.bin: -14 to 954 ftbsf
AC21-B_6in.bin:
The binary files have been depth-shifted to the sea floor (-4934 ft).
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 or 8) 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 15cm, 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
For further questions about the logs, please contact:
Cristina Broglia
Phone: 845-365-8343
Fax: 845-365-3182
E-mail: Crisitna Broglia
Tanzhuo Liu
Phone: 845-365-8630
Fax: 845-365-3182
E-mail: Tanzhuo Liu