With the advent of oil-base and synthetic muds, drilling risks are substantially reduced and efficiency dramatically increased. However, the benefits of microresistivity borehole imagers are lost. The rapid expansion of deepwater activity in unexplored areas has made it even more critical to develop a microresistivity imager tool that operates in these muds to provide key information to geologists for successful exploration. This paper describes the field test results of an innovative microresistivity imager tool that operates in nonconductive drill-in fluids. Based on a new technology, the tool operates in all typical oil-base mud (OBM) types, from diesel to synthetic. The device provides images for formation resistivities ranging from below 0.5 to over 10,000 ohm-m. In addition, the calibrated high-resolution resistivity Rxo provided represents a first in the OBM environment. Four prototypes have been deployed for testing and evaluation in north America and Africa since December 1999, completing more than 50 jobs. In the paper, the principle characteristics of the tool are described. This is followed by two examples. The first well is drilled in a low-resistivity environment in deep water. The second is a highly deviated well in high-resistivity carbonates. Examples of images rich in structural and stratigraphic content are presented. Key indicators of the structural framework and stratigraphic settings are shown to correlate to other data. The variety of facies determined from the images obtained emphasize the usefulness of this new instrument for successful geological interpretation, decision making and risk management in wellbores drilled with OBM.