The physical characteristics of the sedimentary rocks developed in the Gyeongsang basin have been studied based on the geophysical logs which include SP, single electrode resistance, gamma ray, density and caliper logs. The rock sequences penetrated by the borehole, located in the Namji area, are portions of the Chilgok Formation and Jinju Formation which are the base of the Hayang Group and the top of the Sindong Group respectively. Although five different rock types are described on the core log, the boundaries between such rocks are not clearly indicated on the geophysical logs. It is quite apparent that such poorly sorted sediments have non-marine origin and have been severely compacted and almost completely cemented through the diagenesis process. The gamma and SP logs show that the clay content of the formation slightly increases with depth. The organic rich black shale zone of 4m thickness is clearly identified on the gamma-ray log in the top part of the Jinju Formation. The bulk density determined from the density log is about 2.6g/㎤ and does not show much variation between different rock types. This value is close to the expected matrix density of the rock sequences and the rocks are appeared to have very low porosity. The resistivity curve also does not show any clear differences according to the described rock types. This fact also indicates that both shales and sandstones have been severely altered through the diagenesis. The low resistivity peaks and the corresponding large SP deflections are appeared against the fracture zones which are clearly identified on the caliper log. The dominance of such electrokinetic potential over the electrochemical potential also indicates that the permeability of the rocks is very poor.

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