oa Shale Geomechanics - A Nano-indentation Application

Nano-indentation is a technique developed to determine the mechanical properties of small samples. It is based on a hard tip, which is pressed into the surface of a rock sample. The ratio between the applied load and the displacement of the tip into the sample is used to calculate the hardness and Young’s modulus. Additionally, the load-displacement plot obtained from nano-indentation measurements can be used to define three areas which describe the plastic work done on the sample and the elastic work done on the sample. This work-of-indentation approach is a good predictor for the brittleness of shale formation. For the study, core samples were collected from the Toarcian shale formation of the Paris Basin (Couy-1 scientific well) and merged in epoxy resin blocks. First, mineralogical analysis was performed on each block (QEMSCAN analysis) and secondly blocks are used for nano-indentation measurements. Using nano-indentation, for each subsample the Young’s modulus and the hardness are determined. The work-of-indentation approach is utilized in order to predict the brittleness of the samples. Integrating the nano-indentation results with the QEMSCAN data the relation between the mineralogy and the mechanical properties is investigated. Results will presented in details and discussed during the EAGE WS04 workshop.