Pore-Scale Study on Shale Oil–CO₂–Water Miscibility, Competitive Adsorption, and Multiphase Flow Behaviors

Abstract

Due to the fracturing fluid imbibition and primary water, oil−water two-phase fluids generally exist in shale nanoporous media. The effects of water phase on shale oil recovery and geological carbon sequestration via CO 2 huff-n-puff is non-negligible. Meanwhile, oil−CO 2 miscibility after CO 2 huff-n-puff also has an important effect on oil− water two-phase flow behaviors. In this work, by considering the oil− CO 2 competitive adsorption behaviors and the effects of oil−CO 2 miscibility on water wettability, an improved multicomponent and multiphase lattice Boltzmann method is proposed to study the effects of water phase on CO 2 huff-n-puff. Additionally, the effects of oil−CO 2 miscibility on oil−water flow behaviors and relative permeability are also discussed. The results show that due to Jamin's effect of water droplets in oil-wetting pores and the capillary resistance of bridge-like water phase in water-wetting pores, CO 2 can hardly diffuse into the oil phase, causing a large amount of remaining oil. As water saturation increases, Jamin's effect and the capillary resistance become more pronounced, and the CO 2 storage mass gradually decreases. Then, based on the results from molecular dynamics simulations, the influences of oil−CO 2 miscibility on oil−water relative permeability in calcite nanoporous media are studied, and as the oil mass percentage in the oil−CO 2 miscible system decreases, the oil/water relative permeability decreases/ increases. The improved lattice Boltzmann model can be readily extended to quantitatively calculate geological CO 2 storage mass considering water saturation and calculate the accurate oil−water relative permeability based on the real 3D digital core.

Effect of Pore-Throat Heterogeneity on Gas–Water Flow in Tight Gas Reservoirs: From Micro- to Centimeter Scale

“…During stages I and II, the gas–water interfaces are constantly evolving and the interfacial area fluctuates continuously. In contrast, the gas–water interface of stage III remains basically stable, while the interfacial area is maintained stably. , Furthermore, a greater heterogeneity of the pore throat increases the likelihood of a gas snap-off phenomenon. , Microbubbles formed will continue to appear in the fine throat location affected by the Jamin effect, leading to additional seepage resistance and energy dissipation. This is reflected macroscopically by a decrease in the drainage capacity of the water phase and poor gas phase permeability recovery σ = ∑ false⌊ ( false⌊ d i − d̅ false⌋ ) 2 δ i false⌋ / d̅ where d i is the i th pore diameter and δ i is the pore volume ratio.…”

“…The effect of pore-scale heterogeneity on gas–water flow was investigated using the DNS method. ,, The pore disorder coefficient was used to define the degree of heterogeneity of the micromodel , (eq ). Figure shows the geometry and meshing results of the homogeneous, weakly heterogeneous, and complex strongly heterogeneous microfluidic models.…”

Response law and indicator selection of seismic wave velocity for coal seam outburst risk

“…Pore fissure in the coal body is an essential factor that causes the change in longitudinal wave velocity. As a porous material, the closing and generation of fissure in coal and rock is closely related to the stress-strain stage under load (Wang et al, 2023;Xu et al, 2023;Ye et al, 2023). The stress-strain curve of the general coal body loading process can be divided into five sections, and the stress-strain characteristics and wave velocity change characteristics at each stage are shown in Fig.…”

Enhancement of oil transport through nanopores via cation exchange in thin brine films at rock-oil interface

“…Among these potential mechanisms, multicomponent ion exchange was widely recognized as one of the main mechanisms (Bai et al, 2021). Multicomponent ion exchange mechanism is based on a competitive effect of the interaction strength among polar oil components, ions and rock surface (Wang et al, 2023). Thus, the interaction strength characterization of oil/brine/rock interface is both essential for whether the mechanistic study on oil/brine/rock interfacial interaction or enhanced oil recovery.…”