ABI40OBI40 Image Data Processing
IODP-MSP drilling and logging contractor: ESO
Hole: M0023B
Expedition: 310
Location:
Latitude: 17° 29.4191' S
Longitude: 149° 24.2786' W
Logging date: November 11, 2005
Sea floor depth (driller's): 79.45 mbrf (67.58 mbsl)
Sea floor depth (logger's): 79.45 mbrf
Total penetration: 31.12 mbsf
Total core recovered: 21.13 m (64.90 % of cored section)
Oldest sediment recovered: Pleistocene sequence
Lithologies: Reef framework, algal crusts, and microbialite matrix
ABI40 Main/Repeat section: 4.45 – 26.63 mbsf
OBI40: 4.42 – 27.45 mbsf
The OBI40 and ABI40 acquired optical and acoustic images respectively at millimetre scale resolution. The optical images provide continuous and color-calibrated images of the borehole wall with a pixel size of less than 1 mm horizontally by 2 mm vertically. The acoustic images show the acoustic hardness of the lithologies within the coral reef sequence with a pixel size of 1.1 mm horizontally by 4 mm vertically.
The images are displayed as an unwrapped borehole cylinder and are provided in .BMP and .PDF format. 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 to north, hence the strike of dipping features can also be determined. Additional processing on the accelerometer data of the image tools by a double integration of the acceleration allowed, whenever needed, a detailed repositioning of the recorded image data to its correct position with respect to the seafloor.
The ABI40 images of the borehole wall are unaffected by borehole fluid qualit. On the other hand, in regions where the borehole fluid was cloudy OBI40 images are of lower quality with a blurred appearance.
Optical and acoustic images in borehole M0023B are of high quality and enable characterization of lithological changes within the > 20 m of logged section. Optical images are affected by cloudy borehole fluids and large borehole diameters in the lower 3 m only. A loss of power during logging of the acoustic tool necessitated evacuation of the rooster box and logging of the repeat run continued around 10 minutes later.
Additional information about the drilling and logging operations can be found in the Operations section of the Site Chapter in IODP Proceedings of Expedition 310.
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@le.ac.uk