| dc.description.abstract | Source rocks such as resource shale are a special subclass of petroleum
reservoirs where the hydrocarbons are generated and stored in the same place. They
consist of diverse minerology including clays, silt, quartz, carbonates as well as varying
amount of organic material. This diversity creates a multi-scale pore network including
pores down to a few nanometers, micro-cracks and fractures, which influences the fluid
storage and transport in the formation. In this dissertation, initially I present an upscaling
study to gas transport in nano-scale within the organic material of the source rock via
pore network modeling approach. The nanoscale transport effects are linked to the
reservoir scale honoring the multi-physics and multi-scale nature of the formation. The
pore network model is built in accordance with three-dimensional nano-scale imaging of
shale samples where, in most of the cases, the organic material is observed as a network
of pores with some micro-cracks of larger size cutting through, or by the edge of, the
material.
The interaction between the networks of organic pores and micro-cracks could be
important for natural gas production from source rock, because it can control the rates at
which the fluid is transported from the organic constituents of the formation. The matrix-fracture
interactions could also be influenced by the existing in-situ stresses.
Understanding the transient flow behavior would eventually help us optimize
production.
At high pressure, gas is stored in the organic material 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. A modified pressure dependent
definition of a scaled up organic material permeability is obtained taking into account
the previously mentioned factors and using the concept of percolation theory. This
permeability can be used with the classical governing equations of flow and transport.
The coupling term relating the fluid exchange between the organic material and the
associated micro-cracks and fractures is derived and validated through the concept of
dual porosity relating the total fluid exchange to the pressure difference at the fracture-matrix
interface with some modifications to account for the captured transient effect and
the pressure dependency of the gas properties.
At the final part of the thesis, I present a reservoir grid-block scale application of
the derived organic nanoporous matrix-fracture coupling by implementing the
formulation into conventional diffusivity formulation. The results show the retardation
effect on production due to presence of organic nanopores. In addition, the role the
transport mechanisms in the organic material play on the production is analyzed. | en |
