A calculation method for unstable state oil-water relative permeability curve based on ensemble Kalman filter

Key words:  ensemble Kaman filter  relative permeability  unstable slate method  automatic history matching  temperature  inteifacial tension

Abstract:

A calculation method for unstable state oil-water relative permeability curve based on half iterative ensemble Kalman filter (EnKF) was developed. The oil-water relative permeability experiments flooded by high temperature and low interfacial tension system were done. The half iterative EnKF method and JBN method were used to calculate the oil-water relative permeability curves. The effects of temperature and interfacial tension on the oil-water relative permeability were studied. The difference of the results from the two methods is large. But the result from the iterative EnKF is more accurate in the sense of data match. Both the irreducible water saturation and oil relative permeability increase with the increase of the temperature.The residual oil saturation and waler relative permeability decrease with the increase of the temperature. The relative permeability curve moves to the right. Goth the irreducible water saturation and the residual oil saturation decrease with the oil-water interfacial tension decreasing. The flooding mechanisms can be considered in the mathematical model, and the relative permeability obtained from this new method is more suitable to apply in reservoir numerical simulation and production optimization.