A computational methodology to reconstruct the capillary pressure vs saturation curve of rocks through sorptivity tests

Abstract

The capillary pressure curve is a property of rocks whose determination requires elaborate petrophysical measurements. The utility of the capillary pressure curve can be extended to the evaluation of the fluid flow properties of rocks which provides another method for characterization of rocks. In this work we study 1-, 2- and 3-parameter capillary curves models through their effect on the imbibition curves. The 3-parameter model is the usual Van Genuchten family of capillary curves. Each model produces imbibition curves with specific characteristics, encapsulating the behavior of the rock during absorption with increasing detail. Hence, the characteristics of the imbibition curves are associated with suitable regimes of the parameters of each model, thereby providing enough classifying information to determine a suitable capillary curve from imbibition data through back analysis. In order to prove the effectiveness of the methodology we have performed an imbibition test on sandstone and compared it against a series of produced results from finite element analysis for all types of capillary curve models. The degree of coincidence with the experimental imbibition curve is discussed for each model showing the fine differences between the models.