The assessment of rock drillability from elastic and petrophysical parameters

ABSTRACT Rock strength is an essential and effective property in the rock drilling, excavation, and cost evaluation. This work aims to examine a practical approach to evaluate the geomechanical properties that control rock drillability, such as uniaxial compressive strength (UCS) by utilising some petrophysical parameters (porosity and bulk density) and elastic properties (Young’s modulus, bulk modulus, and slowness). To achieve this aim, the study was conducted on some Jurassic rock samples that were cored from different localities in Gebel El-Maghara, North Sinai, Egypt. The uniaxial compressive strength (UCS) was calculated from the measured porosity of 28 sandstone and 89 carbonate plug samples. Empirical equations that relate the uniaxial compressive strength of sandstone and carbonate rocks to physical properties and elastic properties are represented. The physical and elastic parameters that were measured from logging data (sonic, density, neutron, and gamma-ray logs) can be utilised in other future studies to predict the strength of the rock by using these empirical equations that were inferred in this study. The comparison between the relationships of calculated results of UCS in this study with the relationships of laboratory rock strength of different types of sedimentary rocks collected from different places around the worldfrom the previous studies shows high compatibility. The estimated equations from regression analysis of sandstone are more recommended than carbonate.