Standard Wireline Data Processing



Science operator: Texas A&M University

Hole: U1481A

Expedition: 362

Location: Sumatra Seismogenic Zone (Equatorial SE Indian Ocean)

Latitude: 2° 45.2861' N

Longitude: 91° 45.5771' E

Logging date: October 1, 2016

Sea floor depth (driller's): 4189.8 m DRF

Sea floor depth (logger's): 4189.8 m WRF (MSS/HRLA/HLDS/DSI/EDTC/HNGS Downlog)

Total penetration: 5689.8 m DRF (1500 m DSF)

Total core recovered: 219.8 m (62.7 % of cored section)

Oldest sediment recovered: n/a

Lithologies: Clay with silt containing thick beds of fine sand/sandstone with plant fragments and clasts





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 2016.


Logging Runs

Tool string
Top depth (m WMSF)
Bottomp depth (m WMSF)

Casing depth (m WMSF)

No HLDS source. Invalid caliper. Depth reference.
open hole
No HLDS source. Caliper only.
No HLDS source. Caliper only.



In preparation for logging, 350 carrels of heavy mud were pumped in the hole and the bottom of the tool string was raised to about 4251 m DRF (~61 m DSF). Given the concern that the hole might collapse, it was decided to run the HLDS (lithodensity tool) without the nuclear source, along with the spectral gamma ray (HNGS), sonic (DSI), resistivity ((HRLA), and magnetic susceptibility tools (MSS). The Active Heave Compensator (AHC) was used during the entire logging operations. The tool string reached the bottom of the hole without any problem and collected a downlog, main, and repeat pass.


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 (- 4189.8 m). The sea floor depth was determined by the step in gamma ray values at 4189.8 m WRF. This depth coincides with the 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 the downlog.


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. The gamma ray data from the EDTC-B tool were recorded at sampling rates of 5.08 and 15.24 cm. 


Acoustic data. The dipole shear sonic imager (DSI) was operated in the following modes: P&S monopole, upper and lower dipole, and Stoneley (run/pass). The velocities were computed from the DTCO, DT1, DT2, and DTST logs. They are generally of good/low quality.


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). At Hole U1481A the log data is of good quality, with good repeatability between passes.


The gamma ray logs recorded through casing (down to 730 m WMSF) and drill pipe (down to 61 m WMSF) should be used only qualitatively, because of the attenuation of the incoming signal by the thick-walled casing and the thinner-walled drill pipe.


The caliper log shows an enlarged (> 14 inches) and rugged borehole down to 1360 m WMSF. Hole conditions improve substantially in the lowermost 140 m, where the hole is less irregular and the diameter is generally less than 12 inches.


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 360. 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