Investigation of Elastic Properties of Shale Using Digital Rock Techniques - A Case Study

Elastic moduli are important for shale gas exploration and development. However, shale samples from potential reservoirs are usually very brittle and it is very difficult to measure the moduli in laboratory. In this case, digital rock techniques, such as scanning electron microscope (SEM) imaging and finite-element modeling, can be helpful. We apply a digital rock scheme for virtual elastic experiments on a shale sample of high brittleness from a prospective shale stratum in the southeast rim of Sichuan Basin, China. Instead of the usual binary segmentation, we first produce a 2D mineral map, and then divide the map into ten phases, including all minerals with volume fraction >1%. Meanwhile, back-scattering electron (BSE) images of this sample are used to determine the minimal portion of an image that can adequately represent the whole image, i.e., the representative size. Considering the representative size, a 600×600 and a 1200×1200 micron area of the ten-phase image are used for FEM calculation. Despite the limitations of 2D modeling, the calculated elastic moduli are comparable to those from well logs, demonstrating validity of our scheme.