Statistical analysis of heterogeneities and their effect on build-up and drawdown tests

The objective of this work is to determine the effect of permeability and porosity spatial variations on well test pressure response. Data from three wells and synthetic data are used. Field data consist of permeability and porosity as functions of depth and pressure transient test measurements from the same wells. To achieve the objective, two different tools are applied: statistical characterization of heterogeneities and a well test interpretation method. For the data: (1) permeabilities are represented by exponential distribution functions; (2) constant porosity estimates that fit measured transient pressures are almost equal to the statistical arithmetic mean, while constant permeability estimates lie between the median and the arithmetic mean; and (3) minor permeability variations cause important changes in pressure response.