Chevron Gulf of Mexico Gas Hydrate JIP Drilling Program
LWD Sonic Waveforms
Drilling contractor: Chevron
Logging contractor: Schlumberger
Hole: GC955-Q
Expedition: JIP2
Location:
Latitude: 27° 00' 07.3484" N
Longitude: 90° 26' 11.7156" W
Sea floor depth (step in GR log): 6564 ftbrf
Sea floor depth (drillers'): 6567 ftbrf
Total penetration: 8078 ftbrf
ACOUSTIC TOOL USED: sonicVISION
Remarks about
the recording: none.
The sonicVISION
data were acquired by Schlumberger/Anadrill in DLIS format and were uploaded in June 2020 using Schlumberger Techlog software. The waveform data files
were output as LAS files using Techlog and were finally converted into binary files and GIF images using software written in-house. Each of the four waveforms
acquired with the sonicVISION tool consists of 151 samples, at depth
intervals of 2 and 6 inches.
Number of
columns: 605
Number of
rows: 8114 (2-in sampling rate)
Number of rows: 2706 (6-in sampling rate)
The following
files have been loaded:
GC955-Q_2in.bin: -1 to 1351 ftbsf
GC955-Q_6in.bin:
ACOUSTIC TOOL USED: SonicScope
Recording mode: Monopole P&S, Low Frequency
Monopole, Quadrupole.
Remarks about the recording: none.
MONOPOLE P&S MODE: measures compressional slowness
in all formations and shear slowness in fast formations.
LOW FREQUENCY MONOPOLE: for Stoneley
wave analysis.
QUADRUPOLE MODE: measures
shear slowness in slow formations.
The SonicScope
data were acquired by Schlumberger/Anadrill in DLIS format and were uploaded in June 2020 using Schlumberger Techlog software. The waveform data files
were output as LAS files using Techlog and were finally converted into binary files and GIF images using software written in-house.The sonic waveforms are sampled every 20 (monopole
P&S monopole mode) and 40 microsec (quadrupole and low frequency
monopole modes), at depth intervals of 2 and 6 inches. Each of the 12 waveforms
acquired with the SonicScope tool consists of 256 samples.
Number of
columns: 3073
Number of
rows: 8792 (monopole, monopole low-frequency and quadrupole modes, 2-in sampling rate)
Number of rows: 2932 (monopole, monopole low frequency and quadrupole modes, 6-in sampling rate)
The following
files have been loaded:
GC955-Q_scope_mono_2in.bin: -1 to 1464 ftbsf
GC955-Q_scope_mono_6in.bin:
GC955-Q_scope_mono_lf_2in.bin: -1 to 1464 ftbsf
GC955-Q_scope_mono_lf_6in.bin:
GC955-Q_scope_qp_2in.bin: -1 to 1464 ftbsf
GC955-Q_scope_qp_6in.bin:
All values are stored as '32 bits IEEE float'.
Any numerical software or programing language (matlab, python,...) can import the files for further analysis of the waveforms.
The sonic waveform files were depth-shifted to the seafloor (-6564 m).
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 questions about the logs, please contact:
Cristina Broglia
Phone: 845-365-8343
Fax: 845-365-3182
E-mail: chris@ldeo.columbia.edu
Gilles Guerin
Phone: 845-365-8671
Fax: 845-365-3182
E-mail: Gilles Guerin