Empirical Analysis of Density Value Based on Laboratory Test and Geophysical Log on Sedimentary Rock

Abstract

The relationship model of counts per second (cps) and gr/cm 3 has been widely spread, but verification of whether the equation applies to all rocks have not been carried out much. The equation that is widely used in determining the correlation is the Warren equation. However, this equation needs to be verified to ensure whether it can be applied to all materials. This research aims to verify whether the Warren equation can also be applied to clastic sedimentary rocks which have low mechanical properties. This research also seeks to explore the relationship between cps and gr/cm 3 values in clastic sedimentary rocks. The variables in this research include density values resulting from laboratory testing and the measurement result of geophysical logging inside boreholes. The density variable consists of wet density and dry density, while the geophysical log variable consists of long-spaced density (LSD) and short-spaced density (SSD). The analysis was carried out by using regression with heteroscedasticity-consistent standard errors. The result shows that the Warren equation could not be applied to the sedimentary case. Besides, the conversion models of cps to gr/cm 3 for clastic sedimentary rocks that were built had a low predictive ability. Therefore, the determination of rock density is still recommended using laboratory tests of rock samples.