Comparison of indentation test results and well-logging data for estimation of uniaxial compressive strength and Young’s modulus

Abstract

Indentation test results and well-logging data are indirect methods of estimating Young’s modulus (E) and uniaxial compressive strength (UCS). The current study compared the results of indirect methods for a well in an oil field in southern Iran. The indentation tests were conducted by an indenter with a diameter of 260 µn on over 500 drill cuttings. The axial load versus displacement curve was used to determine the indentation modulus (IM) and critical transfer force (CTF) for each drill cutting. Indentation tests were performed perpendicularly and parallel to the weakness surface and were determined CTFV, IMV, CTFP, and IMV. The shear and compressive wave velocity (VS and VP ) for the well-logging data were determined and the UCS and static Young’s modulus (Esta.) were determined. Empirical equations for UCS-CTFV, UCS-CTFP, UCS-IMV, UCS-IMP, Esta-CTFV, Esta-CTFP, Esta-IMV, and Esta–IMP were proposed. It was determined that the relationships between UCS-CTFV and Esta-CTFV were more valid and meaningful than the other relationships. Therefore, it is suggested that the indentation test be performed perpendicular to drill cuttings with a weakness surface. The results showed that the values obtained for CTFV and IMV were 20% higher than for CTFP and IMP.