Effect of AMPS(2-acrylamido-2-methylpropane sulfonic acid) content on the properties of polymer gels

The BST oilfield in the northwestern Taklamakan Desert is a fractured carbonate reservoir, but issues of water breakthrough are becoming increasingly severe with the development of water flooding. Unfortunately, the high-temperature and high-salt conditions (130 °C, 71695 mg/L) of the BST oilfield pose challenges for the development of plugging agents. In this study, the effects of 2-acrylamido-2-methylpropane sulfonic acid (AMPS) content on AM/AMPS copolymers and gels were studied through viscosity measurements, nuclear magnetic resonance (NMR), and cryo-scanning electron microscope (Cryo-SEM). Moreover, the AMPS stabilization mechanism of the polymers and gels was explained. Heat-resistant and salt-tolerant gel systems were developed, and their gelation properties, thermal stability, injection capacity, and plugging ability were evaluated. Experimental results showed inconsistencies between the effects of AMPS content on the polymers and gels. For the polymers, the thermal stability increased with increased AMPS content in the polymer. However, excessive AMPS content resulted in poor gelation and low strength. The developed gel systems with S30 polymer (AMPS content is approximately 26%) exhibited excellent thermal stability, controllable gelation time, good injection capacity, and plugging ability. The field application results indicated that most production wells had a positive response, with reduced water-cut and increased daily oil production.