Estimating Reservoir Heterogeneities from Pulse Testing

Analytical interpretation approaches of interference tests do not yield reliable results about the characterization of reservoirs and determination of flow pattern in fields with a significant degree of heterogeneity. In the present study we report on numerical modeling of pulse testing in the frequency domain. We built a numerical simulator in the Fourier domain for the interpretation of harmonic well tests in strongly heterogeneous reservoirs. The model was used for analyzing the pressure signal at the pulser well and at the observer well and its applicability to determine reservoir heterogeneities was demonstrated. Applications to synthetic and field data are discussed. One synthetic case was a channeled reservoir in which the channel bends and the effective flow path between the two wells in the system were unknown. Another synthetic case concerned a homogeneous reservoir containing a flow barrier. In both cases we successfully quantified the amount of heterogeneity, provided that a basic knowledge about the reservoir characteristics was available. We also applied our technique to a real case, a gas storage field. Here, we were able to exclude the existence of a flow barrier and to quantify the variation in the permeability-thickness kh between the region around the pulser well and that surrounding the observer.