High Quality Electrical Borehole Images While-Drilling Provide Faster Geological-Petrophysical Interpretation, With Increased Confidence.

The drilling environment surprisingly, offers an ideal platform for electrical borehole imaging. At the time of drilling, the borehole wall rugosity is often minimal and electrical images generated by sensors that rotate with the drill string provide a full coverage of the borehole (when compared to the pad coverage observed on conventional wireline borehole images. Field tests and characterization in a laboratory of a new high resolution electrical imaging tool deployed while-drilling confirm its field worthiness as well as accuracy and repeatability of the images. We show further design improvements and conclude that with a properly dimensioned imaging sensor, and use of advanced focusing techniques, a nominal image resolution comparable to that of wireline borehole resistivity imagers may be achieved. With a pixel resolution comparable to that of wireline, we advocate a more confident understanding of the geological features, achieved because of the complete borehole wall coverage. Electrical images from various wells recorded while-drilling show a broad range of high resolution sedimentary features including laminated and disturbed injected/dewatered sands/mud rock, and cross-bedding within laminated and bioturbated sandstones, as well as composite fractures, fracture clusters and faulting. With full borehole coverage textural and facies discrimination is clear and can be extended to the real-time environment and to consider the concept of Sedimentary Steering.