Estimating Permeability Distributions From Pressure Pulse Testing

Abstract

Abstract This work investigated how to utilize multiple frequency components of data from pressure pulse tests to estimate the interwell permeability distribution in an equivalent multicomposite reservoir system. When given pressure time series data in the active well and the observation well, the method of attenuation and phase shift characterizes the reservoir properties without having to know the flow rate. Synthetic homogeneous and heterogeneous reservoir cases were examined under periodic steady-state conditions with multiple sinusoidal inputs and multiple frequencies contained in a square pulse signal. By matching attenuation and phase shift at various harmonic frequencies, the results were found to be in good agreement with the actual permeability distribution trend. The analysis of multiple frequencies is useful in describing the heterogeneity of the reservoir parameters quantitatively, when the radius of cyclic influence is consistent with the sourced frequencies. A new inverse framework of obtaining the permeability distribution by utilizing frequency contents was developed. Attenuation and phase shift of specific frequencies provide the key to describing the reservoir characteristics, and when conditioned on those parameters, the degree of heterogeneity in the reservoir can be revealed. Attenuation and phase shift provide an ‘indicator characteristic’ which can reveal reservoir heterogeneity – without using history matching of pressure, which can be sensitive to noise.