Borehole Seismic Data
Science operator: Texas A&M University
Hole: U1502B
Expedition: 368
Location: China Sea Rifted Margin (South China Sea)
Latitude: 18° 27.8798' N
Longitude: 116° 13.8409' E
Logging date: May 13, 2017
Sea floor depth (driller's): 3774.7 m DRF
Sea floor depth (logger's): 3774.7 m WRF
Total penetration: 4695.5 m DRF (920.8 m DSF)
Total core recovered: 303.75 m (52.7 % of cored section)
Oldest sediment recovered: Late Oligocene
Lithology: Claystone, sand, clay
SEISMIC TOOL USED: VSI (Versatile Seismic Imager)
The logging data was recorded by Schlumberger in LDF/DLIS format. All processing, including first arrival picking and stacking, was performed by Schlumberger during Expedition . The data was then converted into SEGY format at LDEO, using code developed in house. Images of the VSP data in GIF format were created as well.
The tool string included the VSI and the EDTC-B, which was used for depth correlation with the other logging runs: a distinct peak at 4413 m WRF in the GR curve was used.A few stations were attempted in open hole but the tool appeared to be hanging up on a ledge and was unable to pass into the open-hole section. Eight stations were attempted through the 10 3/4 in casing but only six were successful (629, 589, 549, 450, 359, and 290). They delivered a corrected transit time of 2.9386 sec, corresponding to the value expected by the shipboard party.
The heave compensator was not required for any portion of the logging as the total heave was approximately 2 inches throughout the entire operating time.
Stacks are generally calculated with at least nine good traces.
All the data in the SEGY files are sorted shot by shot (i.e. chronologically).
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 368.
For any question about the data or about the LogDB database, please contact LogDB support: logdb@ldeo.columbia.edu.