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1 Lamont-Doherty Earth Observatory, Borehole Research Group, Rte 9W, Palisades, NY 10964, USA goldberg{at}ldeo.columbia.edu
2 Texas A&M University, Ocean Drilling Program, 1000 Discovery Drive, College Station, TX 75845, USA
3 Stress Engineering Services, Inc., 13800 Westfair East Drive, Houston, TX 77041, USA
4 Schlumberger Drilling and Measurements, 135 Rousseau Road, Youngsville, LA 70592, USA
5 Lamont-Doherty Earth Observatory, Borehole Research Group, Rte 9W, Palisades, NY 10964, USA
A newly developed logging-while-coring system was deployed during Ocean Drilling Program legs 204 and 209 off the coast of Oregon and near the Mid-Atlantic Ridge. The system consists of two existing devices modified to be used together — a Schlumberger Resistivity-at-the-Bit* tool, and a Texas A&M University wireline-retrieved core barrel and latching tool. The combination allows for precise core-log depth calibration and core orientation within a single borehole, and without a pipe trip. These tests, conducted in clay-bearing sediments (Leg 204) and in crustal peridotite and gabbroic rocks (Leg 209), mark the first simultaneous use of coring and logging-while-drilling technologies. Sediment cores were recovered with 33% recovery, on average, and as high as 68% to 75 m depth below the sea floor. Core recovery in crustal rocks was only 1–2%, however, penetrating to 21 m depth below sea floor, which is attributed to a problem with the core catcher. High-resolution logs were recorded in the downhole tool memory over the entire drilled intervals at both test sites. It is anticipated that logging-while-coring systems will be utilized more routinely where rig time constraints may otherwise preclude coring in difficult drilling environments.
