Standard Wireline Data Processing



Science operator: Texas A&M University

Hole: U1505C

Expedition: 368

Location: China Sea Rifted Margin (South China Sea)

Latitude: 18°55.0570' N

Longitude: 115° 51.5491' E

Logging date: June 2, 2017

Sea floor depth (driller's): 2928.8 m DRF

Sea floor depth (logger's): 2929.9 m WRF

Total penetration: 3409 m DRF (480.2 m DSF)

Total core recovered: 450.46 m DSF ( 99.7 % of cored section)

Oldest sediment recovered: late Eocene

Lithology: interbedded foraminifera-rich ooze with clay, nannofossil ooze with clay, and clay-rich nannofossil ooze with foraminifera





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 2017.


Logging Runs

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

Depth reference. Caliper closed. Invald LLDS.

open hole



The only tool string deployed in Hole U1505C was modified to include the Dipole Sonic Imager (DSI) acoustic tool. This configuration was chosen as it was not expected, based on experience in nearby holes, that the hole conditions would allow a second run including the FMS and acoustic tool. The plan was to log from total depth at 3409 m DRF 480.2 m DSF) but an obstruction was encountered at 3270 m WRF (340.1 m WSF); all attempts to pass the bridge failed, therefore a repeat and main pass were carried out from that depth.


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 (- 2929.9 m). The sea floor depth was determined by the step in gamma ray values at 2929.2 m WRF. This differs by 1.1  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 thedownlog of the MSS/HRLA/DSI/HLDS/EDTC-B/HNG Stool 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. The HLDS data were corrected hole size respectively during the recording.


High-resolution data. Bulk density (HLDS) data were recorded with a sampling rates of 2.54 cm 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 EDTC-B tool were recorded at sampling rates of 5.08 and 15.24 cm.  Resistivity data are available with a 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 and upper and lower dipole in all passes. After acquisition, the SLB engineer adjusted the DSI labeling range so that it would pick up the correct peaks consistently. The velocities were computed from the delay times.


Quality Control


The quality of the data can be 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). While the DSI labeling certainly improved the quality of the acoustic data, an acceptable correlation with the resistivity data is observed only below 140 m WMSF.


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.


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) and by the FMS tool (C1 and C2). The hole was quite large, with most readings often in excess of 16 inches. The caliper reached its maximum opening in the interval from 96 to 150 m WMSF, therefore the data should be used only from a qualitative stand poimt.


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 368 . 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