Standard Wireline Data Processing
Science operator: Texas A&M University
Hole: U1513E
Expedition: 369
Location: Mentelle Basin (SE Indian Ocean)
Latitude: 33° 47.619' S
Longitude: 112° 29.1204' E
Logging date: 23-24 November, 2017
Sea floor depth (driller's): 2800 m DRF
Sea floor depth (logger's): 2799.5 m WRF
Total penetration: 3574 m DRF (774 m DSF)
Total core recovered: 49.99 m (74 % of cored section)
Oldest sediment recovered:
Lithology: Volcaniclastic siltstone and sandstone, phyric and porphyritic basalt.
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 November 2017.
| Tool string | Run/Pass
|
Top depth (m WMSF) | Bottom depth (m WMSF) | Pipe depth (m WMSF) | Notes |
1. HRLA/DSI/HLDS/EDTC-B/HNGS
|
Downlog 1
|
Through drill pipe |
Caliper closed. Invalid HRLA, DSI and HLDS.
|
||
2. VSI/EDTC-B |
Downlog
|
424 |
11 stations, 33 shots (3 good shots)
|
||
Uplog
|
424 |
||||
3. HRLA/DSI/HLDS/EDTC-B/HNGS
|
Downlog 2
|
424 |
Caliper closed. Invalid HLDS.
|
||
Repeat 2
|
Recorded open hole |
||||
Main 2
|
424 |
||||
4. FMS/APS/DSI/GPIT/EDTC-B/HNGS |
Downlog
|
424 |
Caliper closed. Invalid FMS, APS, and HLDS.
|
||
Repeat
|
424 |
||||
Main
|
424 |
Reference depth.
|
|||
5. HRLA/APS/HLDS/EDTC-B/HNGS |
Downlog 3
|
116 |
Caliper closed. Invalid APS and HLDS.
|
||
Main 3
|
116 |
Drilling and coring at Hole U1513E proceeded without any problems, therefore the hole was expected to be in good conditions for logging. Prior to logging, the hole was conditioned with a sepiolite-seawater based barite mud with a weight of 10.5 lb/gal. Ledges were expected at the sediment basalt interface, therefore a hole finder was added at the bottom of the first tool string, which consisted of HRLA/DSI/HLDS/EDTC-B/HNGS. The drill pipe was set at 3226.5 m DRF (426.5 m DSF). During the downlog the tool string bridged at about 3125 m WRF and some overpull was noticed while trying to pull up the string. Since the pipe was expected to be clear, a mechanical problem was suspected and it was decided to interrupt the downlog and recover the tool string. No damage was observed but as a precaution seawater was pumped down to clean any obstruction in the drill pipe.
The VSI/EDTC-B seismic tool was rigged up next and lowered past the obstruction observed in the previous run. In total 34 shots were fired at 11 stations. Three good shots (at 3440.2, 3374.1 and 3326.1 m WRF were obtained. Gamma ray logs were recorded both downlog and uplog.
The HRLA/DSI/HLDS/EDTC-B/HNGS was lowered again and acquired a downlog with the caliper closed and two uplog passes, a main and repeat, with the caliper open.
The FMS/APS/GPIT/EDTC-B/HNGS tool was run next; it acquired a downlog with the caliper closed and two uplogs, a repeat and main pass.
Finally, a HRLA/APS/HLDS/EDTC-B/HNGS tool string was rigged up, with an inline eccentralizer to keep the porosity tool (APS) pushed against the borehole wall. Eccentralization is a requisite to obtain good porosity measurements, but this practice does not occur often in IODP, as it can increase the risk of the tool string getting stuck in the hole. During this run the drill pipe was pushed up to 2919.3 m DRF (119.3 m DSF) in order to increase the interval of logging in open hole. A downlog and an uplog were acquired without any incidents during this run .
The average ship's heave was around 0.5-1.5 m; the motion heave compensatore was used whenever the tools were in open hole.
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 match and depth shift to sea floor. The original logs were first depth-matched to the gamma ray log from the main run of the FMS/APS/GPIT/EDTC-B/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.
Environmental
corrections. The HNGS
and HRLA data were corrected for hole size during the uplog recording and for bit size during the downlogs. The APS and
HLDS data were corrected for standoff and hole size respectively during the
recording (bit size during the downlogs).
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 EDTC-B tool were recorded at sampling rates of 5.08 and 15.24
cm.
Acoustic
data. The dipole shear
sonic imager (DSI) was operated in the following modes: P&S monopole and upper and lower dipole on all passes. The velocities were computed from the delay times. They are
generally of good quality.
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). Good repeatibility was observed between runs.
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 wide (>12") and/or irregular borehole affects most recordings, particularly those that require eccentralization and a good contact with the borehole wall (APS, HLDS). Hole diameter was recorded by the hydraulic caliper on the HLDS tool (LCAL) and by the FMS tool (C1 and C2). Both show a very good hole, about 11-12 in in size from total depth to about 3300 m WRF (499.5 m WSF). Above thjis depth the hole becomes more variable, ranging between 8 and 12 inches, with local washouts of up to 16 in.
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 369. 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