Standard Wireline Data Processing


IODP logging contractor: USIO/LDEO

Hole: 395A

Expedition: 336

Location: Mid Atlantic Ridge (central tropical N Atlantic)

Latitude: 22° 45.35' N
Longitude: 46° 04.9' W

Logging date: September 24, 2011

Sea floor depth (driller's): 4494 m DRF

Sea floor depth (logger's): 4494 m WRF

Total penetration:  664 m DSF (5158 m DRF, drilled durimg DSDP Leg 45)

Total core recovered: 88.36 m (47.9 % of cored section)

Oldest sediment cored: calcareous brown clay (Upper Miocene)
Lithologies: foram-nanno ooze and calcareous brown clay (sediments), basalt, serpentinized peridotite, and gabbro (basement).




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 September 2011.


Logging Runs

Tool string
Top depth (m WMSF)
Bottom depth (m WMSF)
Pipe depth (m WMSF)
Pass 1 downlog

Casing depth 116 m DSF

Pass 1 uplog
Pass 2 downlog
Pass 2 uplog
603 .5
Pass 3 downlog
Pass 3 uplog



Hole 395A was a re-entry hole. Three logging passes were conducted with the MTT/DEBI-T/GPIT/HNGS tool string without major incidences, except for running onto a ledge at (182 m WMSF) during pass 1. The sea state was relatively calm with a peak-to-peak heave of ~ 0.5 to 1 m. Therefore, the wireline heave compensator was not used during logging.


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 using the sea floor depth of - 4494 m determined by the step in gamma ray values during ODP Leg 174B. All logs from the three passes were then depth matched to the logs acquired during Leg 174B using the gamma ray curve (i.e., HSGR) reference.


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.


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 density 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 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 336. 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