WATER OIL RELATIVE PERMEABILITY COMPARATIVE STUDY: STEADY VERSUS UNSTEADY STATE

摘要

The main objective of this paper is to discuss the methodology and results of a comprehensive study aiming the comparison of water/oil relative permeability curves measured by unsteady-state(USS) and steady state(SS) methods in outcrop rock samples with refined mineral oils.The US and SS comparison work was preceded by a repeatability study followed by a sensitivity study.The sensitivity study evaluated parameters such as oil viscosity,rock permeability and the flow regime(SS or USS) which were combined based on an experimental design. More than 20 tests were performed and analyzed using response surface methodology. The absolute permeability of the rock has been shown to be the most important parameter affecting oil recovery factor and end point permeabilities.As expected,oil viscosity did not present any significant effects up to 100 cp. One important feature of the steady state process is its ability to provide relative permeability information for water saturations below unsteady state water breakthrough. These data may be useful for light oil reservoirs where piston-like displacements often occur.It may also be useful for viscous oil reservoirs since it can provide a more detailed characterization of the displacement in a situation where a water shock front does not develop.Some reservoir simulations were performed in order to evaluate the impact of different processes of relative permeability determination focusing on the prebreakthrough saturation range.