PHYSICAL PROPERTY INTERPRETATION OF SEDIMENTS IN THE SOUTHWESTERN SLOPE OF THE ULLEUNG BASIN, EAST SEA, USING DOWNHOLE LOG DATA

This study focuses on the physical properties of two logged sites (UBGH1-1 and UBGH1-14) in the Ulleung Basin, East Sea. Based on seismic profiles, the upper similar to 50-m layer at logged sites is dominated by turbidite/hemipelagic sediments, whereas the sediments beneath this depth are characterized by thick mass transport deposits (MTDs). Physical property data (velocity, density, porosity, resistivity, and natural gamma) were acquired using Schlumberger's logging tools during logging-while drilling operations. The variation of physical properties at site UBGH1-1 is likely mostly related to consolidation/compaction effects within typical unconsolidated marine sediment types. Repeated turbidite sequences also affect physical property variability. At site UBGH1-14, density and electrical resistivity log data are elevated and constant, respectively, throughout the MTD. In other words, the physical properties of site UBGH1-14 were likely affected by MTD. The overall relationships among the physical properties at both sites generally correlate, but are affected by some data scattering (at UBGH1-14) and clustering (at UBGH1-1). This is thought to result from the different sediment properties within the mass flow deposits (e.g., turbidite/hemipelagic and MTD). Frequency distributions of each property differ for the two sites. This may be indicative of the differences in the sedimentary environments during deposition and/or after deposition.