A Systematic Method to Investigate the EOR Mechanism of Nanospheres: Laboratory Experiments from Core to Micro Perspective

Abstract

Nanospheres have been used as an available plugging material to solve the problem of water intrusion, which is of crucial importance to enhanced oil recovery (EOR). However, the microflow of nanospheres in a low-permeability reservoir is complex, and its plugging performance and EOR mechanism need to be further investigated by a variety of experiments. In this paper, the expansion experiments were given priority to explore the water absorption and salt tolerance of nanospheres. The displacement experiments were conducted to investigate the plugging performance of nanospheres at the core scale. The flow characteristic and EOR mechanism of nanospheres at the microscale were revealed by nuclear magnetic resonance (NMR) experiments and microfluidic experiments. Expansion and displacement experiments results demonstrate that high salinity inhibits the expansibility and agglomeration of nanospheres, and the formation damage and plugging performance of nanospheres should be comprehensively considered. The suitable particle size of nanospheres should be optimized for field application. As for the microscale, NMR experiments revealed that nanospheres would first enter the large pore and then enter the middle and small pores. In microfluidic experiments, the oil recovery increased by 23.02% original oil in place after the injection of nanospheres. The systematic and comprehensive investigations of expansion property, plugging performance, flow characteristic, and EOR mechanism of nanospheres were conducted from core to microscale, which yielded significant insights into preventing water intrusion and enhancing oil recovery.