Influence of Reservoir Pore-Throat Structure Heterogeneity on Water-Flooding Seepage: A Case Study of Yanchang Formation in Ordos Basin

The microscopic pore-throat structure of low-porosity and ultralow permeability sandstone reservoirs controls the seepage characteristics, which directly affects water injection development efficiency oilfields. Different from typical tight reservoirs, macropores mesopores are more developed in this type reservoir, changes dominance micropores over capacity. Based on full-range characterization method fractal theory, many experimental methods used to study influence characteristics Chang 9 reservoir Yanchang Formation Ordos Basin. results 12 samples show that has multifractal occurrence degree movable fluid capacity vary greatly, showing strong heterogeneity. Following structure, relative proportion determines physical properties reservoir. scale structural heterogeneity have a significant impact porosity, while connectivity crucial permeability. Quartz provides resistance compaction preserves primary pores. Additionally, relationship between clay minerals is not significant. Only illite I/S mixed layers slight effect reduction. Furthermore, laumontite cementation key factor destruction structure. Porosity closely related two-phase seepage. Permeability oil displacement anhydrous period, porosity final period. dimension some reflected fact higher homogeneity is, better will be. In particular, macropore guarantees quality. control complex, especially for micropores; stronger significantly affected by as poorer