Data

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 April 2017.

Logging Runs

Tool string	Run	Top depth (m WMSF)	Bottom depth (m WMSF)	Pipe (m WMSF)	Notes
MSS/HRLA/HLDS/HNGS/EDTC-B	Downlog	0	268	110	Caliper closed and invalid HLDS
	Uplog	0	298	110	Reference run

The MSS/HRLA/HLDS/EDTC-B/HNGS tool stringwas rigged up in the usual manner without incident. The tool ran down the pipe without difficulty and exited with ease, but it hung up at approximately 3030 m DRF. After six attempts, the tool finally passed through that depth with significant drag and then continued down smoothly until it reached a depth of 3156 m DRF. The full weight of the tool hung up, and even after several attempts to pass there was no advance as the hole started to collapse. As a result, logging had to be conducted from that depth up. On the way up, there was a significant overpull, approximately 1000 lbs., in the vicinity of 3030 m DRF, and the caliper log indicated that the hole was collapsed to approximately the same diameter as the tool itself at a depth of 3013 m DRF. It was then deemed unsafe to attempt attempt any further runs. The tools were pulled out of hole and rigged down without incident.

The sea state was calm during the logging operation, with an average peak-to-peak heave of less than 0.2 m.

Processing

Depth shift to sea floor and depth match. The original logs were first shifted to the sea floor (-2856.7 m). The sea floor depth was determined by the step in gamma ray values at 2856.7 m WRF. This coincides with 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 of the tool string. The uplog was chosen as the reference run for depth matching.

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, HLDS, and HRLA data were corrected for hole size during the recording.

High-resolution data. Bulk density (HLDS) data were recorded at 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 are 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 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.

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). The overall quality of the data from Hole U1501D is good.

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

The 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 hole is large (>12-16") and irregular between 110 and 190 m WMSF, and it drops to <12" below that depth. As a result, density logs above 190 m WMSF should be used with caution.

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