Modeling Study of Natural Gas Transport and Storage Mechanisms in Shale Formations

Shales are special subclass of producible reservoirs and they are categorized under unconventional resources where the hydrocarbons are generated and stored in the same place. Shales consist of silt, clay and organic materials which influence the mechanisms by which the fluid is being transported and stored. In this proposal, multiscale modeling approach is to be followed to shed light on the intricacies associated with hydrocarbons transport and storage. The nanoscale effects are linked to the macroscopic reservoir scale honoring the multiphysics and multiscale nature of fluid transport in shales. The conceptual model is to be built in accordance with the 3-D nano-scale imaging of shales where, in most of the cases, organic materials can be seen as a network of interconnected round shaped nanopores with some fractures of larger size cutting through them or by the edge of these organic materials. The interactions between these fractures and the organic pores would be of great importance because it allows studying the mechanisms and the rate by which the fluid is transported from the organic constituents of shales. These matrix-fracture interactions are not well understood at the microscopic scale and are greatly influenced by the fluid composition and the degree of confinement. Understanding the transient flow behavior of both compressed and sorbed gas would help optimizing natural gas production in organic-rich shales. At high pressure, gas is stored in the organic materials as a compressed free gas and adsorbed gas. Its transport is driven by pressure gradient with some additional fluxes caused by the degree of confinement and the presence of an adsorbed layer which can be mobile under some conditions of high pressure gradient. The permeability of shale matrix is to be studied taken into account the previously mentioned factors. Additionally, the compositional changes as the reservoir being depleted is to be investigated for better description of phase behavior and flow properties.