Formation imaging using microelectrical arrays is an extremely powerful tool that enables the log analyst, geologist, geophysicist and petroleum engineer to better evaluate complex reservoirs. To date, electrical formation imaging tools with high spatial resolution can image only part of the borehole wall at any one time; attempts to increase borehole coverage have been achieved but with a small degradation of image resolution. A new formation imaging tool has been developed to provide real-time wellsite images of the borehole wall with unprecedented borehole coverage at a resolution of 0.2 in. The borehole coverage of this new tool is 80% in an 8-in. borehole, which represents an increase by a factor of two over previous generation tools. This increase has been achieved while also improving the spatial resolution of the tool. This paper describes the applications of the new tool and the improvement in interpretation of the images. Four tools have been built and tested successfully in wells throughout the world. Examples are given of a fractured formation, a reverse fault, a braided sand and a horizontal well to demonstrate the improvement in the data interpretation.

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