Data

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 January, 2015.

Logging Runs

Tool string	Pass	Top depth (m WMSF)	Bottom depth (m WMSF)	Pipe depth (m WMSF)	Notes
1.MSS/APS/HRLA/HLDS/EDTC-B/HNGS	Down	0	404	84	Caliper closed. Invalid HLDS.
	Repeat	130	450
	Main	0	444	84	Reference run.
2.FMS/DSI/GPIT/EDTC-B./HNGS	Down	0	485	84	Caliper closed. Invalid FMS.
	Repeat	130	450
	Main	0	450	84

After the completion of coring operations hole U1445A was circulated and displaced with 10 ppg barite mud in preparation for logging.The pipe was brought to 2597.9 m DRF (84.8 m DSF).

The MSS/APS/HRLA/HLDS/EDTC-B/HNGS acquired three passes (down, repeat and main) without major incidents. The Wireline Heave Compensator was initially used in the downlog of the MSS/APS/HRLA/HLDS/EDTC-B/HNGS but was disconnected at the end of the repeat pass when it stroked to the full upward position causing a sudden depth offset in the data of 5-6 m. In any case, the sea conditions were very good, with peak-to-peak heave of ~0.2 m, which made the use of the WHC unnecessary. FMS/DSI/GPIT/EDTC-B/HNGS was run next without any problems and also acquired three passes.

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 reading from a 'bottom felt' depth in soft sediment.

Processing

Depth shift to sea floor and depth match. The original logs were first shifted to the sea floor (-2509 m). The sea floor depth was determined by the step in gamma ray values at 2509 m WRF. This differs by 4.1 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 the main run of the MSS/HRLA/HLDS/EDTC-B/HNGS tool string. With the exception of the interval at about 2645 m WRF, where the WHC acted up, there was a remarkable repeatability of the gamma ray data between the six logging runs.

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 APS and HLDS data were corrected for standoff and hole size respectively during the recording. The HLDS does not seem to have been affected by the presence of barite, which usually results in a steady increase of the density log towards the bottom of the logged interval.

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 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 and cross-dipole in all three passes. The velocities were computed from the compressional logs (DTCO). They are generally of acceptable quality. Because the tool was not configured to pick shear wave arrivals effectively, no valid shear slowness is available. Re-processing would be necessary to provide the anisotropy analysis.

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).

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) and by the FMS tool (C1 and C2). The borehole was in relatively good conditions, with most diameter values between 12 and 14 inches from about 225 m WSF to the bottom of the hole and around 14-17 inches in the upper part.

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 353. For further questions about the logs, if the hole is still under moratorium please contact the staff scientist of your 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