| Abstract |
Investigations on numerical treatments and physical processes of fractured two-phase reservoirs were done, based on simple hypothetical reservoir models. In order to maintain a constant power generation, production and reinjection design should be optimal, avoiding heat and fluid depletion. For this, numerical simulation is essential to understand the heat and fluid flow characteristics. For using the MINC approximation which treats fractured media as multiple interacting porous media representing fractures and rock matrices, classification of flow characteristics and hence the numerical treatments are done by using equilibrium times for pressure and temperature in the rock matrix. A zero-dimensional MINC model with no global flow was used to discuss the classification. Then a onedimensional radial flow model was used to investigate reservoir behavior with global flow through fractures. When global flow exists, the difference of vapor saturation between the fracture and rock matrix brings about flow characteristics which are not expected by the zero-dimensional model. If the vapor saturation is different, total mobility of the fluid is different due to the change in relative permeabilities. Fluid and heat supply from rock matrices to the fractures influences the global flow characteristics. Next, in order to investigate the effect of reinjection, a one-dimensional rectangular reservoir model was used. Comparison of the changes in produced fluid enthalpies for fracture models with the same global permeability and fracture spacings but different matrix permeabilities was done. If the matrix permeability is small, vapor saturation in fractures and produced fluid enthalpy rapidly increase initially. Reinjection keeps the enthalpy steady after this early time. The production enthalpy jumps to a higher level when moving the reinjection well further from the producer. If the matrix permeability is large, the reservoir behaves similarly to a porous reservoir, and the enthalpy rise is gradual. This is due to the fluid supply from rock matrix to fractures, and it causes large mass reinjection which reduces the production enthalpy. |