Standard Wireline Data Processing



Science operator: Texas A&M University

Hole: U1523D

Expedition: 374

Location: West Antarctic Ice Sheet (Ross Sea)

Latitude: 74° 9.0288' S

Longitude: 176° 47.7087' W

Logging date: February 2, 2018

Sea floor depth (driller's): 839.0 m DRF

Sea floor depth (logger's): 839.5 m WRF

Total penetration: 1146.8 m DRF (307.8 m DSF)

Total core recovered: 0.90 m (0.5 % of cored section)

Oldest sediment recovered: Late Miocene

Lithology: Diatom-rich mud with interbedded massive and laminated intervals; massive sand and bioturbated mud with common clasts





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 Febraury 2018.


Logging Runs



Tool string
Top depth (m WMSF)

Bottom depth (m WMSF)

Pipe (m WMSF)

Caliper closed. No radioactive source. Invalid HLDS.
Open hole
No radioactive source. Invalid HLDS.

No radioactive source. Invalid HLDS. Reference Run.

Caliper closed. Invalid FMS.
Pass 1
Open hole
Pass 2

Reference Run.


Coring in this hole yielded almost no recovery, indicating hole condition for logging may not be good. As a result, the HLDS density tool was run without the radioactive source and the DSI replaced the APS porosity tool on the tool string. A sepiolite-seawater-barite based mud with a weight of 10.5 lb/gal was added to the hole before logging.

A downlog of the MSS/HRLA/DSI/HLDS/EDTC-B/HNGS tool string was acquired from 775 to 1078.1 m WRF with the caliper closed. A repeat pass and a a main passwere acquired with the caliper open from 1131.6 to 996.8 m WRF and tfrom 1127 to 830.9 m WRF respectively.

A downlog of the FMS/GPIT/EDTC-B/HNGS tool string was aquired from 811.5 to 1228.2 m WRF withthe calipers closed. Two FMS passes were acquired from 1227 to 932.1 m WRF and 1227 to 830.6 m WRF with the calipers open..


The average heave was estimated at 0.2-0.3 m while logging. Themotion heave compensator was utilized whenever the tools were in open hole.




Depth match and depth shift to the sea floor. The original logs were first depth-matched to the gamma ray log of FMS pass 2 before they were depth-shifted to the seafloor. The sea floor depth was determined by the step in gamma ray value at 839.5 m WRF. This differs by 0.5 m from the sea floor depth given by the drillers (see above).


Depth matching is typically done in the following way. One log is chosen as reference (base) log (usually the total gamma ray log from the run with the greatest vertical extent and no sudden changes in cable speed), and then the features in the equivalent logs from the other runs are matched to it in turn. This matching is performed manually. The depth adjustments that were required to bring the match log in line with the base log are then applied to all the other logs from the same tool string.

Environmental corrections. The HNGS and HRLA data were corrected for hole size during the recording.Hole size was estimated with bit size (9 7/8") for this log.Caliper reading (LCAL) was used for hole size correction for both repeat and main passes. The tools were logged up through drill pipe after closing the caliper and raising the drill pipe about 15 m for additional logging.

Environmental corrections. The HNGS and HRLA data were corrected for hole size during the recording using the caliper readings acquired in the main and repeat pass. The HNGS and HRLA recorded in the downlog were corrected using the bit size (9 7/8 in).

High-resolution data. Gamma ray data from the EDTC-B tool and resistivity data from the HRLA tool were recorded at the sampling rate of 5.08 cm, in addition to the standard sampling rate of 15.24 cm.


Acoustic data. The dipole shear sonic imager (DSI) was operated in the following modes: P&S monopole, upper and lower dipole for all three passes. The velocities were computed from the DTCO (compressional), DT1 and DT2 (shear) delay times. The sonic data was of excellent quality. Post-logging reprocessing of the sonic data was done onboard by the Schlumberger engineer on board to improve the labeling.


Quality Control


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 (e.g. the resistivity log should show similar features to the sonic velocity log). All measurements were of good quality, with good repeatability between passes.


Gamma ray logs recorded through the drill pipe should be used only qualitatively because of the attenuation of the incoming signal.


Hole diameter was recorded by the hydraulic caliper on the HLDS tool (LCAL). A wide (>12") and/or irregular borehole affects most recordings, particularly those that require eccentralization and a good contact with the borehole wall (HLDS). The calipers indicated a hole of variable size between 12 and 14 in, with some small washouts to 16-17 in.


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 report, Proceedings of the International Ocean Discovery Program, Expedition 374. For further questions about the logs, if the hole is still under moratorium please contact the staff scientist of the expedition.

After the moratorium period you may direct your questions to:


Cristina Broglia

Phone: 845-365-8343

Fax: 845-365-3182

E-mail: Cristina Broglia


Tanzhuo Liu

Phone: 845-365-8630

Fax: 845-365-3182

E-mail: Tanzhuo Liu