Sample Preparation : Wilcox Shale And Pottsville Shale Samples
Wilcox shale and Pottsville shale samples are tested with the indentation method in this experiment. Both samples are quartz rich and silty shales which contain about 45 to 50% of quartz, 40 to 45% of clays and about 5% of plagioclase. Wilcox shale sample is from Louisiana and formed in upper Cretaceous while Pottsville shale samples are from Alabama and formed in upper Pennsylvanian. These two type of shale rocks are chosen because they are “local” rocks which was abundant and available in the lab, also they have very similar mineralogical compositions.
Both of the shale samples are provide by the SEER lab (Abiola). Before the tests, samples are cut into piece from the core with thickness about 1 in, and polished to make the top and bottom surfaces parallel. All tests are proceed on Nanovea Indenter perpendicular to the bedding direction. As natural material, the shale rock samples are not homogenous, so for each sample, at least 12 tests are done on the sample and averaged to get a result to be statistically correct. The indentation points are chosen carefully using the microscope before each test with the setting conditions shown in table above. Figure below shows the example of the shale sample, indentation line profile and single indentation mark on the sample surface
Figure 2: Example of the Pottsville shale sample (left), indentation line profile (middle) and single indentation mark on the sample surface(right)
Two type of…