Fractures are the main flow channels in naturally fractured reservoirs. Therefore
the fracture permeability is a critical parameter to production optimization and reservoir
management. Fluid pressure reduction caused by production induces an increase in
effective stress in naturally fractured reservoirs. The change of effective stress induces
fracture deformation and changes fracture aperture and permeability, which in turn
influences the production. Coupled interactions exist in the fractured reservoir: (i) fluid
pressure change induces matrix deformation and stress change; (ii) matrix deformation
induces fluid volume change and fluid pressure change; (iii) fracture deformation
induces the change of pore pressure and stress in the whole field (the influence
disappears at infinity); (iv) the change of pore pressure and stress at any point has an
influence on the fracture and induces fracture deformation. To model accurately the
influence of pressure reduction on the fracture permeability change in naturally fractured
reservoirs, all of these coupled processes need to be considered. Therefore, in this
dissertation a fully coupled approach is developed to model the influence of production on fracture aperture and permeability by combining a finite difference method to solve
the fluid flow in fractures, a fully coupled displacement discontinuity method to build
the global relation of fracture deformation, and the Barton-Bandis model of fracture
deformation to build the local relation of fracture deformation.
The fully coupled approach is applied to simulate the fracture permeability
change in naturally fracture reservoir under isotropic in situ stress conditions and high
anisotropic in situ stress conditions, respectively. Under isotropic stress conditions, the
fracture aperture and permeability decrease with pressure reduction caused by
production, and the magnitude of the decrease is dependent on the initial effective in situ
stress. Under highly anisotropic stress, the fracture permeability can be enhanced by
production because of shear dilation. The enhancement of fracture permeability will
benefit to the production of oil and gas.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2010-05-7670 |
| Date | 2010 May 1900 |
| Creators | Tao, Qingfeng |
| Contributors | Ehlig-Economides, Christine, Ghassemi, Ahmad |
| Source Sets | Texas A and M University |
| Language | English |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | application/pdf |
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