Experimental and theoretical investigation of cationic-based fluorescent-tagged polyacrylate copolymers for improving oil recovery

Abstract

The growing need for energy and the depletion of oil wells necessitate advanced Enhanced Oil Recovery (EOR) techniques, particularly water and polymer flooding, which play a crucial role in augmenting hydrocarbon recovery rates. However, water flooding in high-permeability layers often leads to water breakthroughs, reduced sweep efficiency, and the formation of preferential channels, posing significant challenges to oil recovery and reservoir management. Conformance control treatments, including the use of polymer microspheres, offer a promising solution by sealing high-permeability zones and enhancing sweep efficiency. This study focuses on the application of fluorescent polymer microspheres based on polyacrylamide, which is extensively employed in the oil sector as an oil displacement agent. Fluorescent polymers called Poly 400, Poly 200, and Poly 600, incorporating cationic methacrylamide monomers, were synthesized through copolymerization to create amphiphilic polymers with enhanced stability and functionality. These fluorescent polymers were evaluated through flooding tests using a quarter-five-spot model of transparent quartz glass under UV light, allowing for instantaneous measurement and observation of fluorescence intensity. At reservoir conditions, the oil displacement experiments confirm that the incremental oil after water flooding by Poly 400, Poly 200, and Poly 600, is 13.1%, 9.1%, and 6.1% of OOIP respectively. The findings showed that fluorescent polymer microspheres could efficiently target high-permeability layers, adapt to varying pore throat sizes, and improve the plugging rate of high-permeability channels, thereby optimizing oil recovery. A subsequent simulation study using the CMG simulator provided further insights into the efficacy of these fluorescent polymers as EOR agents, revealing their potential to enhance sweep efficiency and enhance oil recovery. Simulation results showed that oil saturation decreased from 68% (initial) to 13.5%, 16.1%, and 18.3% after Poly 400, Poly 200, and Poly 600 flooding respectively. This work highlights the potential of fluorescent polymer microspheres as a valuable tool for EOR applications, offering significant advancements in reservoir management and oil recovery optimization.

Keywords: Enhanced oil recovery (EOR); Fluid flow; Fluorescent polymers; Simulation.

Scheme 1

Synthetic routes of (a) cationic methacrylamide derivatives monomers; (b) synthetic route of cationic methacrylamide-co-acrylamide polymer (poly 600, 400, 200).

Fig. 1

Schematic diagram of 1/4 five spot displacement model of fluorescent polymer.

Fig. 2

(a) FTIR spectra of cationic methacrylamide derivative monomers (P600 and E600), (b), represent FTIR spectra fluorescent polymer (poly600).

Fig. 3

¹H-NMR of fluorescent polymer Poly 600.

Fig. 4

Specific conductivity against the logarithm of polymer concentration, plot for CMC determination.

Fig. 5

(a) Absorption spectra of P400, and P600. (b,c) Fluorescence spectra of P400, and P600 at various excitation wavelengths in water. (d) The changes of fluorescence intensity of P400 with different concentrations.

Fig. 6

The effects of (a) pH, (b) temperature, and (c) ionic strengths on fluorescence spectra.

Fig. 7

Shear/viscosity profile and stress scanning of poly 200, 400, and 600.

Fig. 8

Viscoelastic properties of Poly 200, 400, 600 respectively.

Fig. 9

Cumulative oil recovery with fluorescent cationic polymers.

Fig. 10

Adsorption Retention and Pressure variation as a function of (Pv).

Fig. 11

Cartesian core flood simulation model.

Fig. 12

Modeling of relative permeability using CMG STARS (a) Poly400 (b) Poly200 (c) Poly 600.

Fig. 13

Oil recovery factor from numerical simulation (CMG STARS simulator) for Poly400, Poly200, and Poly 600.

Fig. 14

Oil saturation contours from CMG STARS simulator, showed by 3D Cartesian grids at different periods for the flooding of Poly 400.

Fig. 15

Oil saturation performance during Poly 400, Poly 200, and Poly 600.