Theoretical study on profile control of a nano-microparticle dispersion system based on fracture-matrix dual media by a low-permeability reservoir

In recent years, nano-microparticle dispersion systems have been frequently applied in enhanced oil recovery (EOR) in the low-permeability reservoirs. However, clarification of the profile control process of nano-microparticle has become the focus of this issue in fracture-matrix dual media. The objective of this comprehensive study is to develop a profile control seepage mathematical model of the nanomicroparticle based on fracture-matrix dual media by a low-permeability reservoir. To achieve this, the mass transfer process, convection and diffusion, and three-phase (water, oil, and nano-microparticle dispersion system phases) profile control effect are considered in the dual-media mathematical model inside fracture-matrix low-permeability reservoirs. Besides, we conducted a series of experiments and numerical simulations to demonstrate that the nano-microparticle dispersion system improves the recovery of fracture-matrix low-permeability reservoirs. On the basis of experimental research, it is revealed that the radius ratio (delta) difference between the nano-microparticles and pore throats was the core factor altering the migration characteristics of the nano-microparticle dispersion system. In addition, it is found that the relative permeability curve of the nano-micro particle phase in the micro fractured rock sample is convex. It shows a trend of increasing first and then decreasing, and the common permeation zone becomes wider. The results show that the system selectively enters channels of different formations and achieves step-by-step profile control of the matrix, thereby exhibiting the characteristics of temporary plugging, profile control of microfractures. Finally, a typical reservoir example was then selected for simulation analysis of the effectiveness of the nano-microparticle dispersion system for the improvement of water flooding in fracture-matrix reservoirs. The findings of this study can help for better understanding of the migration behavior of nano-microparticle in the fracture-matrix dual media. It is also possible to design high-quality profile control schemes for fractured low-permeability reservoirs. (C) 2021 The Author(s). Published by Elsevier Ltd.