ABI40 Image Data Processing
IODP-MSP
drilling and logging contractor: ESO
Hole: M0029A
Expedition: 313
Location: New Jersey (NW
Atlantic)
Latitude: 39° 31.1605 N
Longitude: 73° 24.7925 W
Logging
date: July 11 - 16,
2009
Sea
floor depth (driller's): 53.41 m DRF
Sea floor
depth (logger's): 53.26 m WRF
Total
penetration: 754.55
m DSF
Total
core recovered:
454.31 m (74.55 % of cored section)
Oldest
sediment recovered: Early Miocene
Lithologies: Clays to gravels
The acoustic images show the acoustic hardness of the lithologies within the depositional sequence.
In M0029A, acoustic images have been recorded in the lower section of the borehole. Images could not be recorded in the sections above due to time constraints and technical difficulties with the winch. The images from the lower section were recorded at high resolution but the tool was poorly centralized, possibly due to a slightly oversized borehole. The lack of centralisation results in two dark lines occurring at 180° and frequently changing in location. Notwithstanding, the images can be used to recognize major changes in lithology, although average amplitudes and orientation data should be treated with caution. The image logs were acquired in two files but the processed image spectrum data have been combined into a single file due to complete coherency across the files break. The ABI40 images of the borehole wall were apparently unaffected by borehole fluid quality.
The ABI40 acoustic images were
acquired with a resolution of 288
samples x 4 mm which results in a pixel size of less than 5 (horizontal) x 4
(vertical) mm. Acoustic caliper values were calculated by
assuming a acoustic wave velocity of 1495 m/s through
borehole fluid and taking the mean value of the measurements at every sample (4
mm vertical sampling).
The images of the borehole wall (360°),
corrected for decentralization effects when possible, are displayed into a
two-dimensional view as an unwrapped borehole cylinder. A dipping plane in the
borehole will appear as a sinusoid on the image with the amplitude of this
sinusoid proportional to the dip of the plane. The images are oriented with
respect tothe magnetic north, hence the strike of dipping
features can also be determined. A "static" normalization of the
images has been applied to enhance structure visualization. Images are provided
in PDF format at two different scales. The travel time and amplitude data for
each interval logged have also been output in ASCII format.
Additional
information about the drilling and logging operations can be found in the
Operations section of the Site Chapter in IODP Proceedings of Expedition 313.
For further questions about the data, please contact:
Jennifer
Inwood
Phone:
011-44-116-252-3327
Fax:
011-44--116-252-3918
E-mail:
IODP-UK
Johanna Lofi
University
of Montpellier 2
Phone: 033-
467-149- 309
Fax: 033- 467-
143- 244
E-mail:
IODP-UK
For any
web site-related problem please contact:
E-mail:
Database Manager