Logging-while-coring — First results from ODP Leg 204, Hydrate Ridge
Abstract
A new logging-while-coring system, jointly by Lamont-Doherty Earth Observatory, Texas A&M University, and Schlumberger Drilling and Measurements, was deployed and tested during Ocean Drilling Program (ODP) Leg 204 on the Hydrate Ridge off the coast of Oregon. The system consists of a two existing devices modified to be used together - Schlumberger's logging-while-drilling GeoVisionTM resistivity imaging tool and Texas A&M University's wireline-retrieved core barrel and latching/crossover sub-assembly. With this system, resistivity image logs can be recorded while an open annulus is retained through the center of the drilling collar for coring. This test was conducted in 788.5 m water depth in gas hydrate-bearing marine clay and turbidite sediments at the crest of the southern Hydrate Ridge. High quality logs and image data were recorded in the downhole memory over the entire drilled interval and then reprocessed post-cruise using standard algorithms. Using a four-cone bit, coring operations proceeded with sequential 4.5-m, then 9-m-long cores at an average penetration rate of ∼8 m/hr. Eight 58-63 mm diameter cores were collected with 32.9% recovery, on average, from 30 to 74.9 m depth below the seafloor. Recovery reaches as high as 67.8% in one interval. The cores were processed and archived using standard ODP protocols. Core measurements and conventional LWD and wireline logs from the same site compare well to the experimental RAB data. This test marks the first simultaneous use of coring and LWD technologies, an approach that allows for precise core-log depth calibration and core orientation within a single borehole, and without at pipe trip, producing both time savings and unique scientific advantages. Further use of this system in other geological environments is planned for the near future.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA.....1578M