Wireline Sonic Waveform Data
Science operator: Texas A&M University
Location: Mentelle Basin (SE Indian Ocean)
Latitude: 33° 47.619' S
Longitude: 112° 29.1204' E
Logging date: 23-24 November, 2017
Sea floor depth (driller's): 2800 m DRF
Sea floor depth (logger's): 2799.5 m WRF
Total penetration: 3574 m DRF (774 m DSF)
Total core recovered: 49.99 m (74 % of cored section)
Oldest sediment recovered: Older than Late Albian
Lithology: Volcaniclastic siltstone and sandstone, phyric and porphyritic basalt.
ACOUSTIC TOOL USED: DSI (Dipole Sonic Imager)
Recording mode: Monopole P&S and Upper and Lower Dipole (all passes).
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.
UPPER DIPOLE MODE: measures shear wave slowness using firings of the upper dipole transmitter.
LOWER DIPOLE MODE: measures shear wave slowness using firings of the lower dipole transmitter.
Acoustic data are recorded in DLIS format. Each of the eight waveforms geerally consists of 512 samples, each recorded every 10 (monopole P&S) and 40 microsec (dipolemodes), at depth intervals of 15.24 cm (6 inches).The original waveforms in DLIS format are first loaded into Schlumberger's Techlog log analysis package. The packed waveform data files are run through a module that applies a gain correction. After being exported from Techlog in LAS format they are converted into binary and GIF format (images) using an in-house software.
Each row of the binary file is composed of the entire waveform set recorded at each depth, preceded by the depth. In the general case of 8 waveforms with 512 samples per waveform, this corresponds to 1 + 8x512 = 4097 columns. In this hole, the specifications of the files are:
Number of columns: 4097
Number of rows: 3991 (pass 2 downlog)
Number of rows: 3982 (pass 2 main)
Number of rows: 690 (pass 2 repeat)
The following files were converted:
DSI from HRLA/DSI/HLDS//EDTC-B/HNGS (Pass 2 Downlog , drill pipe at 424 m WMSF)
369-U1513E_ldip_d.bin: 0-616 m WSF
369-U1513E_mono_d.bin: 0-616 m WSF
369-U1513E_udip.bin: 0-616 m WSF
DSI from HRLA/DSI/HLDS//EDTC-B/HNGS (Pass 2 Main , drill pipe at 424 m WMSF)
369-U1513E_ldip_main2.bin: 0-614.8 m WSF
369-U1513E_mono_main2.bin: 0-614.8 m WSF
369-U1513E_udip_main2.bin: 0-614.8 m WSF
DSI from HRLA/DSI/HLDS//EDTC-B/HNGS (Pass 2 Repeat , recorded open hole)
369-U1513E_ldip_rep2.bin: 498-616.1 m WSF
369-U1513E_mono_rep2.bin: 498-616.1 m WSF
369-U1513E_udip_rep2.bin: 498-616.1 m WSF
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-matched and depth-shifted to the seafloor (-2799.5 m). Please refer to the 'depth_matches' folder in the hole index page for the depth-matching values and to the "DEPTH SHIFT" section in the standard processing notes for further information.
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
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)
Additional information about the drilling and logging operations can be found in the Operations and Downhole Measurements sections of the expedition report, Proceedings of the International Ocean Discovery Program, Expedition 369. For further questions about the logs, if the hole is still under moratorium please contact the staff scientist of the expedition.
After the moratorium period you may direct your questions to:
E-mail: Cristina Broglia
E-mail: Tanzhuo Liu