Correlations of residual oil distribution with pore structure during the water flooding process in sandstone reservoirs

Abstract

The displacement of residual oil by water flooding in porous media is an important mechanism of enhanced oil recovery in many sandstone reservoirs. Nonetheless, our basic understanding of the influence of complex pore geometries of natural porous media on fluid distribution is still incomplete. Herein, two-phase flow simulations were performed to investigate the pore-scale dynamics of imbibition in a heterogeneous sandstone rock sample. Furthermore, the relationship between residual oil distribution and pore structure parameters was quantitatively characterized based on a pore-throat segmentation method. The findings suggest that the pore-scale displacement and snap-off processes have a strong dependence on the coordination number and aspect ratio. The entrapment and remobilization of oil clusters were also analyzed under continuous and discontinuous displacement modes. In addition, a new quantitative method to evaluate the displacement potential and mobilization pattern of remaining oil was presented and discussed. Statistical analysis revealed that the development of sub-pathways and the suppression of snapoff are responsible for the decrease in residual oil saturation with increasing capillary number during water injection. Moreover, the connected residual oil clusters trapped in pores with high coordination number prefer to be displaced and produced. Finally, the displacement modes with different capillary numbers under different initial oil distributions were evaluated to explain the effect of pore structure. By incorporating these correlations of displacement events with pore-throat geometry, existing predictive models can be improved, which could be helpful for the fine tapping of highly disconnected remaining oil in sandstone reservoirs.

Experimental Study on Factors Affecting Oil Recovery in Sandstone-Buried Hill Superimposed Reservoirs

“…Due to their unique geological characteristics and relatively high oil reserves, these types of reservoirs have increasingly attracted attention. − The connectivity between reservoirs, the heterogeneity, and the strategy of development are the critical factors affecting the efficacy of reservoir exploitation. − Reservoir connectivity can be determined by comparing the differences in well logging curves across various strata between adjacent oil and water wells . It can also be assessed by introducing tracers and detecting their production within the same well group unit to understand the connectivity between injection and production wells. − Additionally, it can be conducted using data inversion methods. − Studies on the impact of interlayer heterogeneity and development methods on development effectiveness can utilize numerical simulations, physical simulations, and mechanistic research, among other strategies. − …”

“… 18 − 20 Studies on the impact of interlayer heterogeneity and development methods on development effectiveness can utilize numerical simulations, physical simulations, and mechanistic research, among other strategies. 21 − 25 …”