Abstract
Anomalous diffusion concept is applied to model subdiffusive flow in heterogeneous, nanoporous media. The basis of anomalous diffusion is discussed and interpreted for heterogeneous flow domains based on the dual-porosity idealization of stimulated reservoir volume around fractured horizontal wells in unconventional reservoirs. Subdiffusion is considered in matrix and natural fractures independently of each other. Two unconventional field examples, one in the Eagle Ford and the other in the Niobrara, are analyzed using the homogeneous and dual-porosity medium idealizations with normal- and anomalous-diffusion models. The analyses by the normal-diffusion model yield estimates of permeability whereas the anomalous-diffusion models provide subdiffusion exponents and phenomenological coefficients of subdiffusive fluxes. It is shown that the dual-porosity, anomalous-diffusion model provides additional information compared to normal-diffusion models, which helps us infer about the reservoir-rock quality and stimulation efficiency.
