Correlative X-ray and Electron Microscopy for Multi-scale Characterization of Heterogeneous Shale Reservoir Pore Systems
Jan Goral, Ilija Miskovic, Jeff Gelb, Mike Marsh, 2016. "Correlative X-ray and Electron Microscopy for Multi-scale Characterization of Heterogeneous Shale Reservoir Pore Systems", Imaging Unconventional Reservoir Pore Systems, Terri Olson
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The complexity of unconventional reservoirs is manifested both in compositional variance of the matrix and the vast heterogeneity of the pore geometry. These complications confound proper understanding of transport properties and, consequently, recoverability for all stages in the production life cycle. Imaging techniques have emerged as a technical solution to aid how we decipher these complexities at the appropriate scales. In this study, we use the Woodford Shale as a representative of a commercially viable unconventional reservoir, and we apply multi-scale imaging analytics to a core sample. Our observations across four different length scales from imaging results of micro-x-ray microscopy (micro-XRM), nano-x-ray microscopy (nano-XRM), and focused ion-beam scanning electron microscopy (FIB-SEM) demonstrate both heterogeneity and anisotropy at every scale. We describe our multi-scale imaging workflow, which proved necessary to capture the multi-scale variability. In this instance of siliceous type II source rock, we find that micro-XRM was insufficient to visualize porosity, nano-XRM was sufficient for visualization of only limited porosity, whereas FIB-SEM yielded the resolved pore network. We further find that discrimination of the pore types, with the aid of image segmentation, helps define the connectivity and nature of the transport system. Collectively, the application of imaging across scales with appropriate image processing is required to adequately understand the transport-governing microstructure.