Calculating the Relative Permeability and the Capillary Pressure Functions from In Situ and Effluent Measurements: An Error Analysis

In this paper we analyze the impact of different types of data on the accuracy of the estimates of the relative permeability and capillary pressure functions from displacement experiments. We calculate the confidence intervals around true relative permeability and capillary pressure curves, and use the area between the upper 95% confidence limit and lower 95% limit to decide which type of data has the largest impact on the accuracy of the estimate. We show that the most sensitive information is provided by the in situ pressure measurements as a function of time. Other in situ type data, such as the saturation as a function of time or several saturation profiles, proves not to be crucial for good estimate, hence the confidence intervals around the true curves for this type of data is quite wide.