The effect of the viscosity-dependent boundary layer on tight oil flow behavior in CO2 Huff-Puff processes: A unified dimensional Pre-Darcy flow model

Abstract

There are numerous percolation studies of unconventional reservoirs showing that in tight or low-permeability formations, the oil flow behavior could be described by the Pre-Darcy mechanism. However, for the CO 2 Huff-n-Puff operations, the most presented low-velocity Pre-Darcy flow models may result in an erroneous evaluation due to the intensive boundary layer thickness changes caused by the CO 2 extraction and dissolution. In this paper, with multiple parameters fitting the seepage experimental results of the studied area, a unified dimensional Pre-Darcy flow model for CO 2 enhanced oil recovery (EOR) is derived from the classic Poiseuille model. Then, the proposed flow model is applied in the compositional simulator for analyzing the viscosity-dependent boundary layer (VDBL) effect, applicability evaluation in Huff-Puff EOR, and field history matching. The results indicate that the VDBL effect improves the oil mobility in injection periods and lowers the residual oil saturation at the front of the CO 2 convection-diffusion area in reproduction periods. Additionally, the nonlinear parameter α and the shape parameter β enhance the proposed model's applicability for the Huff process and the Puff process respectively. Finally, by adjusting the parameters α and β for different permeability intervals of the geological model, the flow model is successfully applied in the oil production matching of the Y6 well, which exhibits its reliability in the history matching. • A unified dimensional flow model is derived from the classic Poiseuille model to characterize the oil seepage behavior. • The proposed flow model is applied in the compositional simulator for analyzing the VDBL effect. • The flow model is successfully applied in history matching of the Songliao tight field in China to exhibit its reliability.