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 February 2010.

Logging Runs

Tool string	Pass	Top depth (m WMSF)	Bottom depth (m WMSF)	Pipe depth (m WMSF)	Notes
1. DIT/APS/HLDS/GPIT/HNGS	Downlog	0	604	102.5	Invalid APS and HLDS
	Uplog	0	606	102.5	Reference
2. FMS/DSI/GPIT/HNGS	Downlog	0	557	102.5	No caliper
	Pass 1	106	606	Open hole
	Pass 2	106	606	Open hole
	Pass 3	0	606	102.5
3. VSI/SGT	Downlog-upper	0	23	In pipe
	Downlog-lower	0	566	102.5
	Uplog	0	19	In pipe

The hole was drilled to a total depth of 3625.2 m DRF and then a wiper trip was made and the hole was displaced with 10.2 lb/gal sepiolite/barite mud for logging. The logging operation began with the DIT/APS/HLDS/GPIT/HNGS tool string, followed by FMS/DSI/GPIT/HNGS and VSI/SGT tool strings. During the uplog of the DIT/APS/HLDS/GPIT/HNGS tool string, a wrap in the cable needed to be re-wrapped at approximately 3446.1 m WRF and the caliper was closed and tool dropped down to correct the wrap. During the VSI run, a single depth checkshot was recorded with sufficient quality at 3621.8 m WSF. Four reasonably good shots were obtained and stacked to make a checkshot travel time of 2386.7 msec. Sea conditions were moderately rough, with a peak-to-peak heave of 1-3 m. The wireline heave compensator was used during the first two logging runs, but not the last one (VSI).

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 shift to sea floor and depth match. The original logs were first shifted to the sea floor (- 3019.5 m). The sea floor depth was determined by the step in gamma ray values at 3019.5 m WRF. This differs by 3.5 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 of the DIT/APS/HLDS/GPIT/HNGS tool string (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.

Environmental corrections. The HNGS and SGT 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.

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 SGT tool were recorded at sampling rates of 5.08 and 15.24 cm.

Acoustic data. The dipole shear sonic imager (DSI) was operated in P&S monopole and upper dipole modes in all 3 uphole passes, using standard frequencies. Only P&S monopole mode was recorded in the downlog. The compressional data (DTCO) were originally good only below 235 m WMSF; they were reprocessed onboard to obtain valid data through the entire interval. The dipole shear data (DT2) were good below 315 m WMSF, but poor above this depth as slowness decreased below the capability of the acquisition software (<775 us/ft). Reprocessing of the shear data is to be performed at a later date.

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 spike in the HNGS gamma ray of the triple combo uplog at 397.5 m WMSF was due to the re-wrapping related winch stop.

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). Porosity logs gave an average value of 60 - 65%. Density values ranged mostly from 1.6 - 1.8 g/cc and PEFL from 2.5 - 4.0 barns/e- with some excursions above 5 and near 10 closer to total depth. Hole diameter was recorded by the hydraulic caliper on the HLDS tool (LCAL) and by the FMS tool (C1 and C2). The hole quality appeared to be fairly good as the caliper read mostly 12-14" from 606 to around 157 m WMSF, at which point the hole size increased to 14-17" up yo the drill pipe at 102.5 m WMSF.

The spherically focused resistivity (SFLU) displayed a slight offset of about - 0.2 ohmm in most of the logged interval, except from 470.5 to 530.5 m WMSF where it tracked the IMPH and IDPH logs.

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 318. 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