Study on ideal oil displacement agents for mobility control based on principle of reservoir chemical flooding energy consumption distribution Ⅰ:flow resistance regulation mechanism and application of surfactant/polymer combination system
In response to the contradiction between the deep mobility control capability and near-well-bore area injectability of oil displacement agents,this paper proposed that an ideal oil displacement agent for mobility control should fulfill the technical require-ments of low viscosity preparation/transportation,low adsorption in the near-well-bore area for long-term stable injection,and pro-duced liquid with low concentrations of the component.Meanwhile,multi-level flow resistance peaks(Δpmax)at different positions in the deep reservoir should be established during the flow process,and flow resistance of fluid after displacing front should be maintained at a lower level.Based on the synergistic effect of the adsorption at the solid/liquid interface and the inter-molecular in-teraction,a hydrophobically associating water-soluble polymer/anionic surfactant binary system was designed with the characteris-tics of dynamically changing the system constituent and microscopic solution structure,thereby changing flow resistance.Com-pared with HP-1(1 500 mg/L),the binary systems HP-1(1 500 mg/L)/SDSB(150 mg/L)and HP-1(1 500 mg/L)/SDSB(200 mg/L),with similar apparent viscosity and different constituents can construct dynamic flow resistance with higher values and bet-ter spatial distribution in the middle-rear position of the porous medium flow during the slug injection and subsequent water flooding processes.It verified that the binary system had the characteristics of viscosity increasing and delayed breakthrough during migra-tion,and the mobility control capability in the displacing front was more powerful.In addition,the spatial distribution of flow resis-tance in the reservoir becomes more reasonable,which prolonged the overall breakthrough time of the slugs,thus expanding the swept volume and enhancing the oil displacement efficiency.Oil displacement experiments were conducted in a Bohai Oilfield with heavy oil,strong heterogeneity,and 80％water cut during water flooding,with chemical industrial products with basically the same dosage and similar cost adopted.The results show that the spatial dynamic distribution characteristics of the binary system be-fore subsequent water flooding breakthrough are a crucial factor affecting oil displacement efficiency,and the binary system(AP-P4(1 400 mg/L)+ZX-27(300 mg/L),viscosity of 6.4 mPa·s)can improve the oil recovery by more than 10％compared with hy-drophobically associating water-soluble polymer AP-P4(1 750 mg/L,viscosity of 62.9 mPa·s).
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