Standard Wireline Data Processing
IODP logging contractor: USIO/LDEO
Location: Canterbury Basin (SW Pacific Ocean)
Latitude: 44 °53.0422' S
Longitude: 171° 50.4065 ' E
Logging date: November 27, 2009
Sea floor depth (driller's): 132.7 m DRF
Sea floor depth (logger's): 133.5 m WRF (DIT/APS/GPIT/HLDS/HNGS downlog)
Total penetration: 1100.7 m DRF (968 m DSF)
Total core recovered: none ( logging dedicated hole)
Oldest sediment recovered: Late Miocene
Lithologies: mud, sandy mud, shell hash, sand, muddy sand, sand (sandstone), shell hash (limestone)
The logging data were recorded by Schlumberger in DLIS format. Data were processed at the Borehole Research Group of the Lamont-Doherty Earth Observatory in December 2009.
|Tool string||Pass||Top depth (m WMSF)||Bottom depth (m WMSF)||Pipe Depth (m WMSF)||Notes|
HLDS not valid
Hole U1351C was a logging dedicated hole. It was drilled to a total depth of 1100.7 m DSF and then conditioned for logging by performing a wiper trip and displacing with 50 bbl of high viscosity mud. Downlog logging was terminated at the depth of 925 m DSF following hole collapse and a trapped wireline cable. After the recovery of the wireline cable and tool string no further logging was carried out. With an average ship's heave of around 1 m, the wireline heave compensator was used for the entire logging operation.
The depths in the table are for the processed logs (after depth shift to the sea floor). Generally, discrepancies may exist between the sea floor depths determined from the downhole logs and those determined by the drillers from the pipe length. Typical reasons for depth discrepancies are ship heave, wireline and pipe stretch, tides, and the difficulty of getting an accurate sea floor from a 'bottom felt' depth in soft sediment.
Depth shift to sea floor and depth match. The DIT/APS/HLDS/GPIT/HNGS downlog was shifted to the sea floor based on the logger's sea floor depth of 133.5 m WRF (step oberved on the GR log at the mudline). This differs 0.8 m from the driller's sea floor depth (132.7 m DRF).
Environmental corrections. The HNGS data were corrected for hole size during the recording.
The quality of the data is assessed by checking against reasonable values for the logged lithologies, by repeatability between different passes of the same tool, and by correspondence between logs affected by the same formation property.
Gamma ray logs recorded through bottom hole assembly (BHA) and drill pipe should be used only qualitatively because of the attenuation of the incoming signal. The thick-walled BHA attenuates the signal more than the thinner-walled drill pipe.
A null value of -999.25 may replace invalid log values.
Additional information about the drilling and logging operations can be found in the Operations and Downhole Measurements sections of the expedition reports, Proceedings of the Integrated Drilling Program, Expedition 317. For further questions about the logs, please contact:
E-mail: Cristina Broglia
E-mail: Tanzhuo Liu