FMI-HD High-Definition Formation Microimager

Building High-Definition into the Measurement

The FMI-HD high-definition formation microimager builds on the well-proven microresistivity imaging approach of the industry-standard FMI fullbore formation microimager. Measurement begins with an applied voltage that causes an alternating current to flow from the array of 192 pad-mounted “button” electrodes through the formation to the upper cartridge housing, which acts as a return electrode.

As the current emerges from a button on the pad or its hinged flap extensions, its path is initially focused on the small volume of the formation directly facing the button. The current path expands rapidly across the formation between the lower and upper electrodes. The current consists of two components:

  • high-resolution component, modulated by the resistivity variations in the formation directly facing the button
  • low-resolution component, modulated by the resistivity of the formation between the lower and upper electrodes.

The microresistivity image of the borehole wall is created from the current measured by the array of buttons. Microresistivity changes related to lithologic and petrophysical variations in the rock, which are conveyed mainly by the high-resolution current component, are interpreted on the image in terms of rock texture, stratigraphic and structural features including dip, and fractures.

FMI-HD high-definition microimager

Accurately imaging the smallest geological subtleties

The spatial resolution of the FMI-HD tool is defined by the button size at 0.2 in. An object larger than 0.2 in appears at approximately its true size. An object much smaller than 0.2 in may also be visible in the image if the object has a resistivity contrast with the surrounding formation, however small, and the imaging tool is sensitive enough to measure the resulting small change in the average formation resistivity within the 0.2-in measurement.

The visibility and interpretability of small features on images from the FMI-HD tool are significantly increased over conventional images for all conditions, even for features that are much smaller than the 0.2-in nominal resolution defined by the button size. For example, the high-definition electronics of the FMI-HD microimager are sensitive enough that fluid-filled fractures less than 10 um in width are frequently imaged. Modern interpretation techniques estimate the size of such small features by quantifying the current flow to the button.

Easily Analyze Dip on High- Definition Borehole Images

FMI-HD High-definition formation microimager
PrevNextZoom1 of 1