UBI Image Data Processing



IODP logging contractor: USIO/LDEO

Hole: U1362A

Expedition: 327

Location: NE Pacific Ocean

Latitude: 47° 45.6628' N

Longitude: 127° 45.6720' W

Logging date: August 12, 2010

Sea floor depth (driller's): 2672 m DRF

Sea floor depth (logger's): 2673.5 m WRF

Casing shoe (driller's): 2980.5 m DRF (308.5 m DSF)

Casing shoe (logger's): 2979 m (downlog); 2981 m (pass1); 2982 m (pass2) WRF

Total penetration:  3200 m DRF (528 m DSF)

Total core recovered: 44.4 m ( 30 % of cored section)

Oldest sediment recovered: N/A

Lithologies:  Highly fractured and altered basalt, both pillow and massive.


UBI Pass 1: 308-506 m WSF

UBI Pass 2: 308-506 m WSF

UBI Pass 3: 372-505 m WSF

Magnetic declination: 17.7213°


The Ultrasonic Borehole Imager (UBI) provides an acoustic image of the borehole wall by scanning it with narrow pulsed acoustic beam from rotating transducer while the tool is pulled up the hole. The same transducer acts as a receiver and measures both the amplitude and transit time of the ultrasonic pulse. The tool is relatively insensitive to eccentralization up to 1/4 in. and in hard formations yields images that are clean and easy to interpret.


The purpose of this report is to describe the images from Hole U1362A and the different steps used to generate them from the raw UBI measurements. The median amplitude and radius measured by the UBI, together with inclinometry and gamma radiation logs from tools on the same tool string are presented with the 'standard' data.


UBI Logging Parameters

Logging Speed (ft/hr)
Frequency (KHz)

Vertical Resolution (inches)

Image Quality
Pass 1
Pass 2

400 and 800

Pass 3



Data Quality


Generally poor to intermediate quality UBI images were obtained from Hole U1362A due to large hole diameter (12-18") for most of the hole section. Smears and truncations in the images resulted largely from downhole tool motion. The images resolved relatively well over the narrower hole section of 456-572 m WMSF. No meaningful UBI image was aquired in the hole section of 388-438.5 m WMSF during Pass 3, due to a bad configuration of the UBI with a 5-1/2" bit size.


The UBI images were depth-shifted to seafloor (2673.5 m WRF) but no depth-match was applied to the images due to technical problems associated with the normalization of depth-matched images using GeoFrame. As a result, the processed UBI images from Passes 1 and 3 are offset about 0.5 m from that of Pass 2 (reference) for few short intervals of the hole.

High angle fractures and foliations can be easily identified in a 360° image display. Moreover, the UBI responds to contrasting physical properties, enabling (for example) differentiation of open and filled fractures.



Image Processing


The following corrections are applied in GeoFrame's BorEID module:


Depth Shift to Sea Foor

The image data is shifted to the sea floor based on the loggers' sea floor depth determined from the step in gamma ray values during the standard data processing.


GPIT Speed Correction

Speed correction corrects for irregular changes in tool speed. Initially, depths are assigned based on the near-constant speed of the cable at the rig floor. The data from the z-axis accelerometer is used to correct the vertical position of the data for variations in the speed of the tool, including 'stick and slip'.


Transit-Time - Radius Conversion

The transit time measurement from the UBI scanner is converted to a borehole radius measurement given the velocity of ultrasound in the borehole fluid, and the tool radius.


Amplitude Eccentering Correction

When the tool is eccentered in a circular borehole, the amplitude is increased in the directions where the distance to the borehole wall is decreased and vice versa. This change in amplitude can often be larger than the changes in amplitude produced by features on the borehole wall that we wish to image. To correct for the effects of eccentering, low order angular harmonic components of the signal with a periodicity equal to 1 and 1/2 revolution are removed.


Transit-Time Eccentering Correction

The transit time signal is corrected in the same way as the amplitude.


Radius Eccentering Correction

The distance and direction of points on the borehole wall are initially given with the tool axis as the origin. The geometrical center of the points on the borehole wall is calculated, and the distance to those points is recalculated relative to the geometrical borehole center. Both corrected (IRBK) and uncorrected (XRBK) radius images are output. The uncorrected image should be used for analyses such as breakouts and dip computations.


Azimuth Equalization

The background response for all azimuths over a large window (e.g. 3m) is equalized, removing preferential enlargement at a particular azimuth, e.g. the keyseat effect.


The following three corrections are minor and will only be apparent in good (circular) borehole sections where the signal shows very small real variations:


EMEX Noise Filter

Gains Calibration

Sampling Bias Correction


Image Rotation

A tool specific rotation is necessary for the UBI to account for the alignment of the transducer (-17° in the case of the current tool).


Depth Adjustments

No depth-match was applied to the images due to technical problems associated with the normalization of depth-matched images using GeoFrame.


Image Normalization

Image normalization is applied using GeoFrame's BorNor module.

In the 'static normalization', histogram equalization is used to obtain the maximum quality image. The amplitude or radius range of the entire interval of good data is computed and partitioned into 256 color levels.

The image can be enhanced when it is desirable to highlight features in sections of the well where amplitude or radius events are relatively subdued when compared with the overall amplitude or radius range in the section. This enhancement is called 'dynamic normalization'. By rescaling the color intensity over a smaller interval, the contrast between adjacent amplitude or radius levels is enhanced. It is important to note that with dynamic normalization, amplitude or radius in two distant sections of the hole cannot be directly compared with each other. A 2-m normalization interval is used.


The normalized images are shifted to a sea-floor reference and converted to gif files using in-house software. They are presented on this website. The image is displayed as an unwrapped borehole cylinder. A dipping plane in the borehole will be displayed as a sinusoid on the image; the amplitude of this sinusoid is proportional to the dip of the plane. The images are oriented with respect to the North; hence the strike of dipping features can also be determined.


Interested scientists are welcome to visit the log interpretation center at /LDEO if they wish to use the image generation and interpretation software.


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 Integrated Ocean Drilling Program, Expedition 327. For further questions about the logs, please contact:


Tanzhuo Liu

Phone: 845-365-8630

Fax: 845-365-3182

E-mail: Tanzhuo Liu


Cristina Broglia

Phone: 845-365-8343

Fax: 845-365-3182

E-mail: Cristina Broglia