| Popis: |
Engineers using numerical reservoir simulators to model fractured reservoirs typically have used straight-line (corner-to-corner) relative permeabilities and zero capillary pressure in the fractures, without a clear understanding of how these two parameters affect simulation accuracy and with no practical method for selecting alternate values. The present study uses the theoretical work of Rossen and Kumar (non-straight-line fracture relative permeabilities)1,2 and of Firoozabadi and Haugh (non-zero capillary pressure in rough-walled fractures)3 to quantify prediction errors and to demonstrate a method for selecting the correct set of relative-permeability and capillary curves for a particular simulation. Our results indicate that using straight-line relative permeabilities can lead to predicted oil-recovery errors as high as 70% in water-oil systems and to underestimating oil production times in some gas-oil systems by as much as a factor of three. In gas-oil systems where gas flows into the fractures, oil recovery from the matrix blocks could be underestimated by a factor of almost two when fracture capillary pressures are set at zero. |
