Abstract
To study the displacement law of polymer flooding in fluvial reservoirs, physical simulation cores are designed according to the characteristics of strong planar heterogeneity in such reservoir systems. Three different polymer solutions, namely, partially hydrolyzed polyacrylamide (HPAM), hydrophobically associating water-soluble polymer (AP-P4), and long-term shear retardant polymer (LSRP), are analyzed through oil displacement experiments. The results show that, in the simulated fluvial reservoir core model, the sweep efficiency of water flooding is about 80%, but the recovery is only about 20%, with poor oil displacement efficiency. The effects of HPAM and AP-P4 on improving sweep efficiency are poor, as they cannot effectively sweep the low- and medium-permeability areas on either side of the central core. The polymer LSRP, which has higher viscosity and better viscoelasticity, can effectively expand the sweep volume, with the sweep efficiency reaching 97.8%, but there is still the potential to greatly improve the oil displacement efficiency. The results indicate that, in fluvial reservoirs under the experimental conditions, expanding the sweep volume requires high-performance polymer solutions. The enhanced oil recovery method is required to obtain a greater oil displacement effect. The results provide a reference for the selection of displacement agents for the development of fluvial reservoirs.
Highlights
The heterogeneity of a reservoir has an important influence on its development
Li et al.19 established a heterogeneous model with a preferential channel according to the geological characteristics of a block in the Daqing Oilfield, China
A hydrophobically associating watersoluble polymer (AP-P4) was purchased from Guangya Company, Sichuan, China. This is a new type of water-soluble polymer that is formed by introducing hydrophobic groups into the hydrophilic main chain of partially hydrolyzed polyacrylamide
Summary
The heterogeneity of a reservoir has an important influence on its development. In water flooding, differences in the oil–water viscosity ratio can result in water phase fingering. The heterogeneity of the reservoir aggravates this phenomenon, and is not conducive to reservoir development, such as in fluvial reservoirs. Li et al. established a heterogeneous model with a preferential channel according to the geological characteristics of a block in the Daqing Oilfield, China. According to the geological characteristics and well-pattern model of narrow channel reservoirs in the BZ oilfield, Zhou et al. constructed a large plane physical model to study the water flooding effect. These studies have shown that there is no standard physical model of fluvial reservoirs. To highlight the influence of fluvial reservoir characteristics on fluid flow, this paper describes the design and construction of a physical model of heterogeneous plane permeability. The performance of the different polymer solutions under the conditions of plane heterogeneity of fluvial deposits is studied, providing a reference for the selection of displacement agents for the development of fluvial reservoirs
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