Standard Wireline Data Processing

Science operator: Texas A&M University

Hole: U1569A

Expedition: 396

Location: Mimir High (North Eastern Atlantic Ocean)

Latitude: 65° 49.8775' N

Longitude: 2° 1.6081' E

Logging date: August 29, 2021

Sea floor depth (driller's): 2182.4 m DRF

Sea floor depth (logger's): 2183.6 m WRF

Total penetration: 2583.3 m DRF (400.9 m DSF)

Total core recovered: 139.28 m (35.6 % of cored section)

Oldest sediment recovered: Early Eocene

Lithology: Clay with silt.

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 August 2021.

Logging Runs

Tool string	Pass	Top depth (m WMSF)	Bottom depth (m WMSF)	Pipe depth (m WMSF)	Notes
1. MSS/HRLA/HLDS/HNGS	Downlog	0	127	82	Caliper closed. Invalid HLDS.
	Uplog	0	128	82	Depth reference.

In preparation for logging, the hole was displaced with heavy mud. Logging operations in Hole U1569A originally included the MSS/HRLA/HLDS/HNGS and FMS/DSI/GPIT/HNGS tool strings, as well as the VSI/HNGS. The MSS/HRLA/HLDS/HNGS was lowered first and hung up first at 70 m WRF and then again at 1620 and 2005 m WRF and near the near the tip of the drill pipe, possibly due to RST debris. After reaching the open hole section of the hole, the tool string reached a maximum depth of 2311 m WRF ( m WSF), where it got stuck again. Since no progress was made to free the tool string, the shipboard party decided to end the logging operations. The tools returned to the surface without further incidents, after recording a brief section uphole.

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.

Processing

Depth match and depth shift to sea floor. The original logs were first depth-matched to the gamma ray log from the uplog pass of the MSS/HRLA/HLDS/HNGS tool 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.

The depth-matched logs have then been shifted to the sea floor. The sea floor depth was determined by the step in gamma ray values observed on the uplogs at 2183.6 m WRF. This differs 1.2 m from the sea floor depth given by the drillers (see above).

Environmental corrections. The HNGS and HRLA data were corrected for hole size during the recording. The drill bit value was used, as no caliper measurement was acquired.

High-resolution data. No good density data were acquired, as the caliper was closed because the tool string was only one tool string length in the open hole section of the hole. The HRLA was acquired every 5.08 cm; in the database it is resampled at 15.24 cm, for ease of comparison with the other logs.

Quality Control

The quality of the data is usually 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). In hole U1569A only a very short section was recorded open hole. There is good repeatability of the resistivity and gamma ray logs between downlog and uplog.

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.

The conditions of the hole could not be assessed directly from the caliper measurement, as none was recorded. However, the frequents obstruction encontered during the logging operations indicate that the hole must have been in very poor condition and prone to collapse.

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 396. 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