Pre-Darcy flow behavior of CO2 Huff-n-Puff development in Fuyu tight formation: Experiment and numerical evaluation

Abstract

There is growing evidence showing that the oil phase seepage in tight matrix obeys the low-velocity Pre-Darcy flow because of the boundary effect between pore wall and fluid. However, most Pre-Darcy flow model may cause inaccuracy in simulating the reduction of non-linear degree, because of oil properties improvement caused by CO2 injection. In this paper, we propose a newly Pre-Darcy model with dynamic non-Darcy parameter c1 to characterize the tight-oil non-linear flow behavior in CO2 Huff-n-Puff process. Firstly, based on the high accurate experimental data in flow velocity testing with representative cores in Fuyu reservoir, non-linear parameter c1 is modified as a two-parameter function of tight oil flow capability. Then, the validated self-developed compositional simulator with embedded-discrete-fracture model (EDFM) and unstructured perpendicular bisection (PEBI) grid system is applied in field-scale cases to compare this proposed newly Pre-Darcy flow model with other previously presented flow models. Based on the comprehensive simulation comparison, the results show when the oil properties improvement occurs in injected-CO2 swept and diffusion area, the proposed Pre-Darcy flow model can properly describe the reduction of non-linear degree, leading to additional 0.45% oil recovery in three-cycle Huff-Puff operation. Additionally, in this newly dynamic flow model, capillary pressure in nanopores could degrade the non-linear degree of oil phase, which exhibits typical advantages on production well performance. Finally, this Pre-Darcy flow model is successfully applied in history matching of Fuyu Oilfield to validate its reliability.