Investigating Effects of Chelating Agents on Viscoelastic Surfactant Flooding at the Pore Scale Using Micromodels

Viscoelastic surfactants (VES) have proven their suitability for enhanced oil recovery (EOR) because they increase the viscosity and decrease the interfacial tension (IFT). In this work, we are proposing chelating agents to suppress the effect of salinity and maintain the required value to build the viscosity to optimize the amount of VES needed for a successful EOR job. Two different VES concentrations were investigated, 0.5 and 1.25 wt %. The chelating agents were diethylenetriaminepentaacetic acid (DTPA) and glutamic acid diacetic acid (GLDA), with different chelating agent concentrations ranging from 2 to 8% for each VES concentration. Rheology results showed that, for DTPA, the highest viscosity at the working shear rate of 1 s-1 is 717 cP achieved by 6% DTPA with 1.25% VES. While for GLDA, the highest viscosity at the working shear rate is 738 cP achieved by 8% GLDA with 1.25% VES. On the other hand, the IFT results for GLDA showed the lowest value of 0.0022 mN/m at 4% GLDA with 1.25% VES, and for DTPA, the lowest value was 0.0068 mN/m at 8% DTPA with 1.25% VES. The microfluidic recovery test was done for the selected best performance in IFT and rheology for each chelating agent with the pure VES. The ultimate recovery from 4% GLDA with 1.25% VES is 56% out of the original oil in place, while 43% using 8% DTPA with 1.25% VES. The pure VES at 1.25% gave 48% ultimate recovery. The chelating agent proved to be successful in suppressing the effect of salinity in reducing the IFT. Therefore, normal seawater without sweetening can be used with VES and GLDA and achieve promising recovery.

Automated summary

Viscoelastic surfactants (VES) are used in enhanced oil recovery (EOR) to increase viscosity and reduce interfacial tension (IFT). This study proposes the use of chelating agents to suppress the effect of salinity and optimize the amount of VES needed for successful EOR. Experimental results show that using 6% DTPA with 1.25% VES achieves the highest viscosity, while using 4% GLDA with 1.25% VES achieves the lowest IFT. Microfluidic recovery tests demonstrate that using 4% GLDA with 1.25% VES leads to a 56% ultimate recovery. Overall, the chelating agents have been successful in reducing salinity and achieving promising recovery. Rating: 8/10.