3.1. Sample Alteration Both types of shale rock consist on a broad scale quartz, feldspar, plagioclase, calcite, dolomite, pyrite, chlorite, kaolinite, and illite. Marcellus shale has long been known as a major source rock, while Pottsville shale is potential caprock for CO2 storage. X-ray diffraction (XRD) experiments were conducted on both shale samples by Olabode and Radonjic for the compositional data. Comparing the source rock and caprock, both rocks has similar tectosilicates content (quartz and feldspar) around 50%. The main differences are in carbonate and clay content. Marcellus shale is carbonate- rich (~27%) with clay content of 22%; while Pottsville shale has no carbonate content and 46% of clay minerals. With a further look on the clay content, Pottsville shale have significant amount of chlorite (10%) which Marcellus have none (Olabode and Radonjic, 2017). Chlorite is capable of trapping CO2 permanently under the solid form as it reacts with CO2 and forms siderite, dolomite and kaolinite (Gaus, 2010). 3.2. Micro Indentation Miro indentation tests were conducted on these two types of shale rocks perpendicular to the bedding direction. All samples are cut into piece from the core with thickness about 1 in, and polished to make the top and bottom surfaces parallel. Each sample was tested with at least 25 points and …show more content…
The calculation of mechanical properties is made assuming surface before indentation is perfectly smooth. In fact, during the polishing process, harder phases like quartz or chlorite can be polished easily, but softer phases like kaolinite and illite tend to have scratches or even get pulled out. Most literature deal with similar materials merged the sample into epoxy, but the fact that it fills the pores of the porous material is an alteration of the microstructure as well as the mechanical