Capillary end effects in coreflood calculations

Abstract

Capillary end effects in coreflood experiments, in some cases, can significantly influence the computation of end-point relative permeabilities and final saturation levels. Because capillary end effects arise from capillarity, these corrections for relative permeability and saturation can be quantified if the capillary pressure curve is known a priori. Based on Darcy's law and the relative permeability–capillary pressure relationships, we present in this paper how these corrections can be done in corefloods if the in situ saturation profile is unavailable. Under the same principle, if the in situ saturation profile of the capillary end is available, it is therefore possible to simultaneously predict both relative permeability and capillary pressure using pressure data. Such a method of prediction is presented in the paper and experimentally verified. In a reservoir-conditioned oilflood using a carbonate core sample, we obtained the capillary end information through in situ microwave monitoring, and the relative permeability and capillary pressure were predicted based on the theory. The predictions were compared with separate capillary pressure (mercury injection, porous-plate, and centrifuge) and relative permeability (steady-state) measurements. The predictions and experiments agree well with one another.