Standard Wireline Data Processing


IODP logging contractor: USIO/LDEO

Hole: U1331A

Expedition: 320

Location: Equatorial Pacific Sediment Mound (Eastern Equatorial Pacific)

Latitude: 12° 4.089 ' N

Longitude: 142° 9.698 ' W

Logging date: March 17-18, 2009

Sea floor depth (driller's): 5127.3 mbrf

Sea floor depth (logger's): 5133.5 mbrf

Total penetration: 5317.9 mbsf

Total core recovered: 154.89 m (81.3 % of cored section)

Oldest sediment recovered: Middle Eocene

Lithologies:  Radiolarian ooze with clay, nannofossil ooze, chert



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 March 2009.


Logging Runs

Tool string Pass Top depth (mbsf) Bottom depth (mbsf) Pipe depth (mbsf) Notes




 Logging operations were originally planned with the MSS/HLDS/HNGS/GPIT tool string, but the GPIT tool was soon removed from the string due to incompatibility of communication between the HNGS and the GPIT i.e., the GPIT must go below the HLDS, rather than the HNGS). As a result, the MSS/HLDS/HNGS string was used for logging. No problems were encountered during the first downlog pass, but the subsequent uplog pass was completed when the clutch of the wireline winch experienced episodic slipping during most of the logging session. This resulted in erratic logging speed that may have somehow affected the data quality. The FMS/DSI/GPIT/HNGS tool string was not deployed due to the probelms related to the erratic cable speed and winch.

The WHC was not used throughout logging operations because of some technical problems with the WHC flying head, which stroked completely out beyond the range of the magnetic sensor on the flying head. The sea state remained relatively calm during the logging operations, with heave of less than 1 meter.

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 (- 5133.5 m). The sea floor depth was determined by the step in gamma ray values at 5133.5 mbrf on the MSS/HLDS/HNGS uplog. This differs by 6.2 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 uplog pass of the MSS/HLDS/HNGS tool string. The uplog pass was chosen as the reference pass because it was the only pass to cross the sea floor.

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 data were corrected for hole size during the recording. The HLDS data were corrected for standoff and hole size respectively during the recording.

Magnetic susceptibility data. The magnetic susceptibility tool (MSS) was run for the first time during Expedition 320 (after the sea trial test of Expedition 320T). At the time of this processing the recorded data has not been calibrated yet and therefore is not presented in the online database. It will be included at a later date.

High-resolution data. No data recorded in high resolution mode.


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).

Despite the lack of calibration of the susceptibility log, there is generally good correlation between the downlog and uplog passes for the low resolution susceptibility logs. More processing is required to produce final results.

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.

Hole diameter was recorded by the hydraulic caliper on the HLDS tool (LCAL). The caliper was kept closed during the downlog and open during the uplog. In the upper 50 meters of the open hole the caliper reached its maximum opening at about 18 inches, while in the lower part the hole is generally smaller and quite irregular.

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 320. 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