Review on Phase Behavior in Tight Porous Media and Microscopic Flow Mechanism of CO₂ Huff-n-Puff in Tight Oil Reservoirs

Table 2

Summary of microscopic flow mechanisms by NMR.

Research contents	Reference	Main conclusions
Oil flowing process	Ma [23]	The crude oil in the large pore is first produced, and then the crude oil in the small pore is gradually produced under the action of concentration difference and molecular diffusion.
	Wang et al. [57]	The crude oil flows out to the core surface due to the expansion of CO2. The oil in each pore can be mobilized with the increase of the exposure time in the first exposure experiment.
Residual oil distribution	Chen et al. [58]	After CO2 displacement, residual oil was mainly distributed in pores with pore diameter below 0.1 μm.
Permeability	Xiao et al. [59]	Reducing the damage of asphaltene deposits to the core permeability is very important for improving oil recovery factor.