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.