Experimental study on a new plugging agent during CO2 flooding for heterogeneous oil reservoirs: A case study of Block G89-1 of Shengli oilfield

• Synthesis and evaluate a granule channeling sealing agent during CO2 flooding.
• This system is suitable for low permeability and low water-cut oil reservoirs.
• The system had good performance of sealing for CO2 and improved EOR by 11.9%.

In oilfield operations, CO2 has been applied to enhance oil recovery (EOR). However, CO2 injection in heterogeneous oil reservoirs lacks acceptable sweep efficiency due to the high mobility of CO2. A suitable composite organic granule plugging agent was developed to control CO2 mobility and hence, improve sweep efficiency and oil recovery. The reaction mechanism involved hydroquinone, formaldehyde, furfural and heptyl alcohol catalyzed by p-toluene sulfonic acid at supercritical CO2 to initiate carbonyl addition and condensation reaction via sol-gel polymerization to form granulated polymer. This system is suitable for low permeability and low water-cut oil reservoirs. The core experiments show that the system is easy for injection, and the plugging ratio is more than 98% after injecting 1PV. The parallel sand pack model experiments show that the system can enter the high permeability reservoirs first and as the increase of permeability ratio, the profile modification becomes better. The core flooding experiment shows that the system had good performance of sealing for CO2 and the EOR can be further improved 11.9% at the same time.