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Coupled Hydro-Mechanical Simulation of Multi-Phase Fluid Flow in Fractured Shale Reservoirs Using Distinct Element Method
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- Author / Creator
- Nazary Moghadam, Saeed
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In the present research, a numerical method was developed to solve the equations of motion of coupled hydro-mechanical multi-phase fluid flow through fractured unconventional reservoir rocks with particular application to the simulation of shale reservoirs stimulation by water injection. To this end, a finite volume discrete fracture-matrix approach was developed to numerically formulate flow of immiscible multi-phase fluid, comprised of aqueous and non-aqueous liquids along with dissolved and free gas, through both pore spaces and complex fracture networks. Using this method, compressible multi-phase fluid flow under viscous forces, gravity and interfacial tension was simulated taking into account matrix-matrix, matrix-fracture and fracture-fracture multi-phase fluid transmissibility. An objected oriented C++ code called Finite Volume Black Oil Simulator (FVBOS) was written to implement the developed discrete fracture-matrix approach.
In order to simulate the effects of interaction of solid phase deformation and multi-phase fluid flow, mathematically represented by the coupling between multi-phase flow velocity field and solid phase displacement field in the equations of motion, a novel sequential hydro-mechanical coupling method was developed. In this method, during each time step of fluid flow analysis performed by the discrete fracture-matrix method, aperture and normal stiffness of fractures are iteratively updated based on the displacement field of solid phase obtained by three-dimensional Distinct Element method. The matrix porosity is assumed to be constant during the analyses since the hydro-mechanical coupling is mainly due to the interrelationship between pore fluid pressure and fracture aperture in shale reservoirs. Using distinct element method, fractured porous media is represented by a densely packed system of blocks separated by complex deformable fracture systems facilitating the simulation of slippage and detachment of intact blocks along and across the fractures. To implement the developed coupled hydro-mechanical multi-phase fluid flow simulation approach, Multi-Phase Discrete Element Simulator (MPDES) was developed by linking FVBOS and 3DEC, Itasca’s Three-Dimensional Distinct Element Code, using multi-process programming method.
The coupled hydro-mechanical multi-phase fluid flow through fracture and matrix has not been properly simulated so far in the framework of discrete element approach. In the present research, an enhanced discrete element method was developed to address this shortcoming with particular application to coupled hydro-mechanical modeling of stimulation of shale reservoirs by water injection. The developed computational model makes it feasible to numerically analyze the coupled hydro-mechanical multi-phase fluid flow in both porous matrix and fractures in reservoirs where complex deformable fracture systems are encountered. The developed computational tool paves the way to more sophisticated approaches for the efficiency assessment of hydraulic fracturing and production schemes in shale reservoirs. -
- Graduation date
- Fall 2020
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
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