This paper addresses the use of the Spearman rank coefficient, a nonparametric statistical method, to estimate lateral autocorrelation and permeability trends. This approach provides an alternative to interference tests considering only production and injection rates. The objectives of this work are to validate this technique, point out its advantages/limitations and show results from its application to a field. We performed a set of numerical experiments using a flow simulator and different synthetic permeability fields. The results highlight the dependence of the proposed method on reservoir parameters. The method can indicate the presence of transmissibility barriers, permeability anisotropy and, in some situations, range anisotropy. Next, we present a field case to demonstrate the application of the method. The Canto de Amaro field, located in the Potiguar basin, Brazil, is chosen because of a small well spacing and a previous comprehensive reservoir characterization study using geostatistics. The results obtained provide a better understanding of how rank :analysis can be used as an effective reservoir characterization tool.