New Application of Rebound Hardness Numbers to generate Logging of Unconfined Compressive Strength in Laminated Shale Formations

摘要

This study explores the application of an Equotip Hardness Tester (EHT) to unconventional shale formations for the purpose of estimating unconfined compressive strength (UCS) and further developing the logging of UCS derived by the EHT. This application of EHT overcomes the limitation of intact core recovery required for preparation of test specimens with standardized geometry for traditional rock mechanics laboratory tests where laminations in shale often prevent test specimen preparation. The EHT can measure the rebound hardness numbers (RHN's) to estimate UCS on the surfaces of both intact and laminated/cracked cores. Initial validation of the process was performed using aluminum specimens with six different lengths. Extensive RHN's measurements and UCS tests were conducted to develop new empirical equations for conversion of RHN's to UCS. The UCS log estimated by RHN's can be used to further calibrate petrophysical models and contribute to frac design by discriminating fracable zones and frac barriers.