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Ritter, René N.1, Volker Krueger1, Matthias Gorek1, Christian Fulda1, Stephen A. Morris2, Jeremy Lofts2, Ansgar Baule1, Roland Chemali3 
(1) Baker Hughes INTEQ, Celle, Germany 
(2) Baker Atlas, Aberdeen, United Kingdom 
(3) Baker Hughes INTEQ, Houston, TX

ABSTRACT: High Quality Electrical Images While Drilling Open a Wider Window on Near Wellbore Geology

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 of a new high resolution electrical imaging tool while-drilling confirm its field worthiness as well as accuracy and repeatability of the images. We show that with a properly dimensioned imaging sensor, and use of advanced focusing techniques, a nominal image resolution comparable to that of excepted wireline borehole resistivity imagers may be achieved. The sensor is currently applicable to conductive mud only. In a series of controlled runs we have compared the response of the “While-Drilling” tool with its wireline counterpart, and to offset well cores. Although the pixel resolution of the “while drilling” imager is comparable to that of the wireline, a better understanding of the geological features is achieved through the complete borehole wall coverage. Electrical images recorded while-drilling show high resolution sedimentary features including laminated and disturbed mud rock, cross-bedding within laminated and bioturbated sandstones, composite fractures and fracture clusters. With full borehole coverage textural and facies discrimination is clear. Characterization in a laboratory environment has also been performed. This includes imaging through a set of two artificial formations and across and interface of known dip and a across simulated fracture. The electrical diameter value is demonstrated to be comparable with wireline electrical imaging tools.

 

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.