There is growing evidence showing that because of the interact between pore wall and fluid, the oil seepage in tight porous media conforms to low-velocity non-Darcy flow. However, in the process of CO2 Huff-n-Puff development, Darcy model or previously published low-velocity non-Darcy flow model with constantly non-linear parameter in most numerical simulator may cause inaccuracy in simulating the variation of non-linear degree since the mobility improvement of oil phase contacted with the injected CO2.

In this paper, a dynamic non-Darcy flow model linked to phase behavior calculation with capillary pressure is firstly presented that uses dynamic non-linear parameter, C1. Furthermore, two mechanism cases with unstructured-perpendicular-bisection (PEBI) grid and fractures presented by embedded-discrete-fracture model (EDFM) are established to respectively validate self-developed simulator and discuss the comparison of Darcy model, previously published non-Darcy model and dynamic non-Darcy model. Additionally, the effect of nanopores on dynamically non-linear degree is analyzed. Finally, field history matching of dynamic non-Darcy flow in actual field-scale model is conducted. Research shows that the dynamic non-Darcy flow model can properly describe the reduction of nonlinear degree of oil phase in the gas-injection swept and diffusion region. In addition, nanopores exhibits typical advantages on oil recovery because capillary pressure has the ability to degrade the non-linear degree of oil phase. Finally, this dynamic non-Darcy flow model enables to make the evaluation in well performance and bottom hole pressure more accurate.

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