Self-regulating profile control strategy for CO2 flooding by the phase-transition acid

To solve the problem of low sweep efficiency caused by gas channeling in CO₂ flooding, the CO₂ stimulated response liquid–solid transition system (TA-D230) was designed by the tetradecanedioic acid (TA) and poly(propylene glycol) bis(2-aminopropylether) (D230). TA, which has high melting point and is insoluble in water, achieves the transition from solid phase to liquid phase by the self-assembly method with D230. After CO₂ injection, the TA was precipitated from TA-D230 solution as the solid. The transformation mechanism from TA-D230 to TA was confirmed by ¹H NMR and FTIR due to the reduction of COO⁻ group to COOH group. The TA exhibited a high melting point of 128 °C by the DSC, which can be applied in high temperature reservoirs. In addition, by recording the changes in conductivity and pH during the injection of CO₂, 0.1 mol/L TA-D230 achieved rapid precipitation within 5 min and in a 5000 ppm NaCl solution. The core flooding experiment further assessed that TA-D230 has excellent ability to enhance oil recovery with a value of 15.3 %. This method provides a new perspective and solution for profile control in oil and gas development.