Scaling of counter-current imbibition processes in low-permeability porous media

Oil recovery from low permeability reservoirs is strategically important because of the large resources locked in such formations. Imbibition is fundamental to oil recovery from such reservoirs under most secondary and improved recovery processes of practical interest. It is also characteristic of porous medium wettability. The rate and the extent of imbibition depend critically on the viscosity of the wetting and nonwetting phases. In this study, recent work is presented regarding imaging imbibition in low permeability porous media (diatomite) with X-ray computed tomography. The viscosity ratio between nonwetting and wetting fluids is varied over several orders of magnitude yielding different levels of imbibition performance. A mathematical analysis of counter-current imbibition processes is performed and a modified scaling group is developed that incorporates the mobility ratio. This modified group is physically based and appears to improve scaling accuracy of countercurrent imbibition significantly. (C) 2002 Elsevier Science B.V. All rights reserved.