Standard Wireline Data Processing



Science operator: Texas A&M University

Hole: U1466B

Expedition: 359

Location: Maldives (Central Equatorial N Indian Ocean)

Latitude: 4° 55.988' N

Longitude: 73°1.6894 ' E

Logging date: October 25, 2015

Sea floor depth (driller's): 528 m DRF

Sea floor depth (logger's): 528 m WRF (downlog), 527 mWRF (uplog)

Total penetration: 1346 m DRF (808 m DSF)

Total core recovered: 88.54 m (17.9 % of cored section)

Oldest sediment recovered: Lower Miocene

Lithology: Lithified/partially lithified dolomitic grainstone with bioturbation





The logging data was recorded by Schlumberger in DLIS format. Data were processed at the Borehole Research Group of the Lamont-Doherty Earth Observatory in October 2015.


Logging Runs

Tool string
Top depth (m WMSF) Bottom depth (m WMSF) Pipe depth (m WMSF) Notes
No nuclear source and closed caliper. Invalid HLDS. Reference.
No nuclear source and closed caliper. Invalid HLDS.



In preparation for logging, Hole U1467C was swept with heavy mud. The tool string, consisting of the MSS/HRLA/HLDS/EDTC-B/HNGS tools, was rigged up without nuclear source due to concerns about hole stability and the potential risk of losing a source in Maldivian territorial waters. The downlog encountered a hole obstruction at about 894 m WRF (366 m WSF), which the tool string was unable to pass. Data was collected upward and then the hole was abandoned.


The sea state was calm, therefore no Wireline Heave Compensator (WHC) was used.


The depths in the table are for the processed logs (after depth shift to the sea floor and depth matching between passes). 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 original logs were first shifted to the sea floor (- 528 m). The sea floor depth was determined by the step in gamma ray values at 528 m WRF. This corresponds to the sea floor depth given by the drillers (see above). The depth-shifted logs have then been depth-matched to the gamma ray log from thedownlog of the MSS/HRLA/HLDS/EDTC-B/HNGS tool string.


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.


High-resolution data. Gamma Ray data from the EDTC-B tool were recorded at sampling rates of 5.08 and 15.24 cm. 


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). In Hole U1466B repeatability between the two passes is poor, as a result of sudden variations in wireline tension during both passes. Both gamma ray and resistivity data must be used with caution.


The 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.


Hole diameter could not be recorded because the hydraulic caliper on the HLDS tool (LCAL) was not opened due to the poor hole conditions and the risk of getting the tool string stuck downhole.


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 359. 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