Shape Factor for Compressible Fluid Flow in Fractured Reservoirs
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Supervisors: Dr. Chen, Dr. Hassanzadeh
Shape factor for slightly compressible fluids is a function of fracture spacing or matrix block size and geometry, and also a time-dependent parameter. A shape factor is necessary to compute the fluid transfer from matrix to fracture during numerical simulation of flow in fractured reservoirs using dual porosity approach.
Conclusively, the approximate semi-analytical solution is validated with fine-grid numerical simulations. Shape factor demonstrates a transient behavior and then converges to a constant value during the pseudo steady-state period for a compressible fluid. The average value of the stabilized dimensionless shape factor for compressible gas flow under a constant fracture boundary condition was found to be 8.5 as compared to π2 for a slightly compressible fluid. Stabilized value of the matrix-fracture transfer shape factor for a compressible fluid is a weak function of the temperature and the gas specific gravity. The pressure variation shows a negligible effect on the stabilized value of the shape factor. The results revealed that the matrix-fracture transfer shape factor for a compressible fluid in the dual-porosity media is a function of the pressure depletion regime in the fracture. Based on the pressure depletion regime in the fracture the stabilized value of the shape factor varies between two limits. The upper limit is obtained for a linearly declining fracture pressure (slow pressure depletion regime). The lower limit is derived for the constant fracture pressure boundary conditions (depletion takes place faster).