Wireline Sonic Waveform Data
Science operator: Texas A&M University
Hole: U1508C
Expedition: 371
Location: Tasman Sea
Latitude: 34° 26.8905' S
Longitude: 171° 20.2558' E
Logging date: August 31, 2017
Sea floor depth (driller's): 1619.7 m DRF
Sea floor depth (logger's): 1617 m WRF (MSS/HRLA/DSI/HLDS/HNGS/EDTC-B downlog)
Total penetration: 2324 m DRF (704.3 m DSF)
Total core recovered: 163.12 m (66.5 % of cored section)
Oldest sediment recovered:
Lithology: Gray nannofossil chalk with forminifers
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 on a virtual PC machine using Schlumberger's Techlog log analysis package. The packed waveform data files are run through a module that applies a gain correction. After they are exported from Techlog in LAS format, they are converted into binary and GIF format (images) using in-house software.
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 + 8x512 = 4097
columns. In this hole, the specifications of the files are:
Number of
columns: 4097
Number of
rows: 4280 (downlog)
Number of rows: 2854 (main pass)
The following
files have been loaded:
DSI from
HRLA/MSS/DSI/HLDS/EDTC-B/HNGS (Downlog, drill pipe at m 87.5 WMSF)
371-U1508C_ldip_d.bin: 0-660 m WSF
371-U1508C_mono_d.bin: 0-660 m WSF
371-U1508C_udip_d.bin: 0-660 m WSF
DSI from
HRLA/MSS/DSI/HLDS/EDTC-B/HNGS (Main pass, recorded open hole)
371-U1508C_ldip_main.bin: 263-706 m WSF
371-U1508C_mono_main.bin: 263-706 m WSF
371-U1508C_udip_main.bin: 263-706 m WSF
DSI from
HRLA/MSS/DSI/HLDS/EDTC-B/HNGS (Repeat pass, recorded open hole)
371-U1508C_dip_rep.bin: 572-706 m WSF
371-U1508C_mono_rep.bin: 572-706 m WSF
371-U1508C_udip_rep.bin: 572-706 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 (-1617 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.
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 = 4*(1+nrec*nsamples))
where nrec is the number of receivers (8 in the case of the DSI) and nsamples the number of samples per waveforms.
If the total number of depths where waveforms were recorded is ndepth (for a 150 m interval with data every 15cm, ndepth would be 1001), a generic loop to read the data would be
do k = 1, ndepth
...
read(1, rec=1+k) depth(k), ((data(i,j,k), j=1,nsamples),i = 1,nrec))
...
enddo
the first record in each file is a header with some of the file specifications:
- number of depths
- number of samples /trace
- number of receivers
- tool number = 0 (DSI)
- mode (1 = Lower Dipole, 2 = Upper Dipole, 3 = Stoneley, 4 = Monopole)
- vertical sampling interval
- scaling factor for depth
- waveform sampling rate in microseconds
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 . 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:
Cristina Broglia
Phone: 845-365-8343
Fax: 845-365-3182
E-mail: Cristina Broglia
Tanzhuo Liu
Phone: 845-365-8630
Fax: 845-365-3182
E-mail: Tanzhuo Liu