Standard Wireline Data Processing


IODP logging contractor: USIO/LDEO

Hole: U1438D

Expedition: 351

Location: Amami-Sankaku Basin (Philipine Sea)

Latitude: 27 ° 23.0218' N

Longitude: 134° 19.1023' E

Logging date: June 19, 2014

Sea floor depth (driller's): 4711 m DRF

Sea floor depth (logger's): 4708.5 m WRF (HRLA/APS/HLDS/EDTC-B/MSS/HNGS downlog)

Total penetration: 5608.8 m DRF (897.8 m DSF)

Total core recovered: 77 % of cored section (upper 257 m cored in U1438B, with 88% recovery)

Oldest sediment recovered: Eocene

Lithologies:  Mud with ash, turbidites, conglomerates, breccia, sandstone




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 June 2014.


Logging Runs

Tool string
Top depth (m WMSF) Bottom depth (m WMSF) Pipe depth (m WMSF) Notes

Closed caliper. Invalid APS/HLDS. Reference Run.




After drilling completion, the hole was conditioned with sepiolite-based mud. Because drilling conditions were good, similar conditions were expected for the logging operaions. The pipe was pulled to 300 m DSF before dropping a free fall funnel. Afterwards, the ship moved 20 m to the north and the drill bit was released. Re-entering the hole was difficult but it finally succeeded.

The HRLA/APS/HLDS/EDTC-B/MSS/HNGS tool string was lowered without probems to a depth of 5021 m WRF, where it encounterd a bridge. After several attempts to pass the bridge it was decided to start logging up. Because the bridge depth corresponded to the depth of the drill pipe during the deployment of the free fall funnel, it was believed that the drill pipe itself caused the bridge. The pipe was then lowered to 5039 DRF (19 m below the obstruction) and the drill string was lowered again. However, it encountered a new obstruction at 5080 m WRF, at which point it was deemed safe to stop logging and retrieve the tool string.


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 (- 4708.8 m). The sea floor depth was determined by the step in gamma ray values on the downlog at 4708.5 m WRF. This differs by 2 .5 m from 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.

Note that before depth-matching there was a mismatch of about 6-7 m between the two passes.


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; since the caliper was closed during the downlog, the bit size was used instead.The APS and HLDS data were corrected for standoff and hole size respectively during the recording.


High-resolution data. Bulk density (HLDS) and neutron porosity (APS) data were recorded sampling rates of 2.54 and 5.08 cm, respectively, in addition to the standard sampling rate of 15.24 cm. The enhanced bulk density curve is the result of Schlumberger enhanced processing technique performed on the MAXIS system onboard. While in normal processing short-spacing data is smoothed to match the long-spacing one, in enhanced processing this is reversed. In a situation where there is good contact between the HLDS pad and the borehole wall (low-density correction) the results are improved, because the short spacing has better vertical resolution. Gamma Ray data from the SGT 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 and porosity log).


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 wide (>12") and/or irregular borehole affects most recordings, particularly those that require eccentralization and a good contact with the borehole wall (APS, HLDS). Hole diameter was recorded by the hydraulic caliper on the HLDS tool (LCAL). The hole is enlarged and more irregular down to about 165 m WMSF, smoother but enlarged (mostly above 16 in) from 160 to 270 m WMSF and sometimes below bit size in the bottom 20 m interval. Overall, the hole size was not ideal for logging and the quality of the density and porosity logs was affected by the lack of contact with the borehole wall.


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 351. For further questions about the logs, please contact:



Tanzhuo Liu

Phone: 845-365-8630

Fax: 845-365-3182

E-mail: Tanzhuo Liu


Cristina Broglia

Phone: 845-365-8343

Fax: 845-365-3182

E-mail: Cristina Broglia