Imbibition capillary pressure curve modelling for two-phase flow in mixed wet reservoirs
Research output: Research › Master's Thesis
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) and methods and techniques available to evaluate capillary pressure curves in such a media 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 gathered from an artificially created 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 the non-wetting and wetting phases. This process is performed using a combination of a correlation and a centrifuge experiment. The correlation is modelled and implemented in Maple and support with a tool established in Visual Basic. The 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 saturation data is used in the model as a first trial, to evaluate if the procedure can work and the presented model leads to acceptably results. The performed curve fitting achieves high accuracy to match the model with generated test data used to create the saturation profile. Follow ups for field application of the developed Maple tool are proposed and an outlook for the difficulties facing three phase flow is given.