Wireline Sonic Waveform Data
Science operator: University of Rhode Island-University of Milano
Logging operator: Schlumberger Italy
Hole: Cismon (APTICORE Program)
Location: Monte Grappa State Road 50 (km 53), Veneto, Italy
Latitude: 46° 2' 43.46" N
Longitude: 11° 45' 46.85" E
Logging dates: January 17-18, 1996
Elevation (ground level): 398 m
Total penetration: 131.8 m
Lithologies: limestones.
ACOUSTIC TOOL USED: SDT ( Sonic Digital Tool, also known as Array Sonic)
Recording mode: Depth-Derived Borehole-Compensated mode, with a 3'-5'-5'-7' spacing.
Each of the 4 waveforms consists of 500 samples, acquired at depth intervals of 15.24 cm (6 inches). The original waveforms were first loaded on a virtual PC machine using Schlumberger's Techlog log analysis package, then they were exported from Techlog in LAS format and finally converted into binary and GIF format (images) using in-house software. Gain cirrections were applied. Each line is composed of the entire waveform set recorded at each depth, preceded by the depth value. In the general case of 4 waveforms with 500 samples per waveform, this corresponds to 1 + 4x500 = 2001 columns. In this hole, the specifications of the files are:
Number of columns: 2001
Number of rows: 873 (main run)
Number of rows: 378 (repeat run)
The following files have been created:
SDT from SDT/NGT (main run)
cismon_m.bin: 8-131 m
SDT from SDT/NGT (repeat run)
cismon_r.bin: 8-56.54 m
All values are stored as '32 bits IEEE floating point'.
Any image or signal-processing program should allow to import the files and display the data.
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 Cajon Pass project is available at:
https://riviste.unimi.it/index.php/RIPS/article/view/5330/5382
https://people.clas.ufl.edu/jetc/files/Channelletal2000GSAB.pdf
https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2009PA001769