Wireline Standard Data Processing


DSDP operator and logging contractor: Scripps Institution of Oceanography

Hole: 613

Leg: 95

Location: Baltimore Canyon (NW Atlantic)

Latitude: 25° 13.3' N

Longitude: 85° 59.5' W

Logging date: October 1983

Sea floor depth (drillers' mudline): 2333.2 mbrf

Sea floor depth (step in GR log): logs did not reach the mudline

Total penetration: 581.9 mbsf

Total core recovered: 357.97 m (78.3 % of cored section)

Oldest sediment cored: early Eocene

Lithologies: calcareous mud, sands, nannofossil chalks, limestone, porcellanite.




The logging data was recorded by Schlumberger in LIS format. Data were processed at the Borehole Research Group at the Lamont-Doherty  Earth Observatory in.


Logging Runs


Tool string Pass Top depth (mbsf) Bottom depth (mbsf) Bit depth (mbsf) Notes
Reference run
LSS/GR only
LSS/GR only



The tool string was lowered to the bottom of the hole through some bridges in the hole. The lower and upper passes recorded the full sonic waveforms (but no data from the other tools). The Lamont Multichannel Sonic (MCS) tool was also run and collected 82 m of open-hole logs.


The depths in the table are for the processed logs (after depth matching between passes and depth shift to the sea floor). 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 the 'bottom felt' depth in soft sediment.




Depth match and depth shift to sea floor: The original logs were depth-matched to the GR log from the main pass of the DIT/LSS/GR/MCD tool string, and were then shifted to the sea floor (-2333.2 m). The DIT/LSS/GR/MCD main pass was chosen as the reference run because it covered the whole open hole interval. The DT logs from the other passes were matched to the DT log from the reference run.


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 sea floor depth could not be determined from the logs because they did not extendto the sea floor. The driller's seafloor depth of 2333.2 mbrf was used to shift the logs to the sea floor.


Sonic data: The transit time data were processed using an in-house program that compares the slowness derived from the 8 different transmitter-receiver combinations at each depth, and discards those times that are significantly different from the majority as bad data. The 'points' column in the LSS data files is a measure of confidence:  it records the number of transmitter-receiver pairs retained - a value of 8 means that no data was discarded.  This processing leads to improved compressional wave velocity logs that are free of the artifacts present in the velocities derived directly from DT and DTL.


Gamma ray data:  The GR log was corrected for borehole diameter.


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).


A wide (>12") and/or irregular borehole affects most recordings, particularly those that require eccentralization and a good contact with the borehole wall (FDC, CNL). Hole diameter was recorded by the 3-arm MCD tool (CALI). The caliper for the DIT/LSS/GR/MCD main pass read about 9 inches for the majority of the hole, narrowing to less than 5 inches at 173-175, 221-232,  and 398-400 mbsf.


A null value of -999.25 may replace invalid log values.


Additional information about the drilling and logging operation can be found in the Operations section of the Site Chapter in DSDP Initial Reports volume 95. For further questions about the logs, please contact:


Cristina Broglia

Phone: 845-365-8343

Fax: 845-365-3182

E-mail: Cristina Broglia