Imbibition capillary pressure curve modelling for two-phase flow in mixed-wet reservoirs

Abstract

Until the early 2000s, the majority of reservoirs worldwide were considered to be either water-wet or oil-wet and capillary pressure correlations were developed subsequently. Recently, it was shown that most reservoirs are mixed-wet (Anderson 1986, Delshad et al. 2003, Lenhard and Oostrom 1998) where available methods and techniques to evaluate capillary pressure curves are limited. To advance on this topic, the current thesis deals with the modelling of capillary pressure curves in two-phase, mixed wet reservoirs and proposes a way to evaluate capillary pressure experiments. The proposed method aims to obtain both positive and negative imbibition capillary pressure curves using saturation profiles gained from a centrifuge experiment. The saturation data of the core sample obtained from a centrifuge experiment is used to determine the following parameters: residual oil saturation, irreducible water saturation, pore size distribution indices as well as the capillary entry pressure for both phases. This process is performed using a combination of a correlation modelled and implemented in Maple with a support tool established in Visual Basic. A centrifuge experiment is simulated in Maple and imbibition capillary pressure hysteresis curves are produced using the concept by Skjæveland et al. (1998), which is the preferred correlation for mixed-wet reservoirs. Artificially created centrifuge data is used in the model leading to reasonable results. Curve fitting is performed with high accuracy to match the model with lab data used to create the saturation profile. Follow ups for field application of the developed Maple tool are given and an outlook for three phases is proposed.