CO<inf>2</inf>-responsive preformed gel particles with interpenetrating networks for controlling CO<inf>2</inf> breakthrough in tight reservoirs

Abstract

Horizontal well re-fracturing of tight reservoirs triggers complex fractures, which induces severe gas channeling and low sweeping efficiency in CO2 flooding due to the significance difference in permeability between matrix and fractures. Herein, novel CO2-responsive preformed gel particles with interpenetrating networks (IPN-ASSAP) was synthesized to mitigate CO2 breakthrough. To reveal the plugging efficiency and EOR potential of IPN-PAASP, the change in particle size distribution, microstructure, strength, and rheology were characterized, followed by core flooding experiments. Experimental results indicated that after IPN-ASSAP contacted with CO2, the median diameter and strength of particles were enhanced due to protonation reaction of IPN-PAASP. Moreover, after IPN-PAASP was injected into fractured core, injection pressure increased from 5.0 kPa to 0.342 MPa with plugging efficiency of 99 %. During water flooding and CO2 flooding, the crude oil in fracture was displaced with oil recovery of 17.1 %. After plugging was formed, injected CO2 entered matrix, and recovery factor increased by 23.1 %. All the experiment results indicated that IPN-PAASP is a promising candidate for fracture plugging during CO2 flooding.