Preparation and Mechanism of Stability for High-Temperature and High-Salinity Gels

Abstract

Summary By using an acrylamide (AM)-acrylamide propyl sulfonate (AMPS) copolymer crosslinked with hydroquinone (HQ) and hexamethylenetetramine (HMTA), a stable gel was prepared at 150℃ in simulated brine with a salinity of 25×104 mg/L. The gelation time, strength, and thermal stability of gel were investigated, and the results indicated that the dosage of the crosslinker was the key factor controlling the stability and gelation time of gel. When the polymer concentration was more than 0.7 wt% and the concentrations of HQ and HMTA were more than 0.2 wt%, respectively, a gel aged under high temperature and high salinity for 180 days could be obtained, but its gelation time was short and could be extended by adding lauramidopropyl hydroxy sulfobetaine (LHSB). When the crosslinker concentration was low, the gel would exhibit syneresis problems after aging at 150℃. Cryo-scanning electron microscopy (cryo-SEM), 13C nuclear magnetic resonance (13C-NMR), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR) analyses showed that the presence of AMPS in the crosslinked polymer controlled the gel resistance to high temperature and high salinity. Using AM-AMPS copolymer with high AMPS content and regulating the crosslinker concentration can effectively inhibit the intramolecular catalytic hydrolysis of AMPS and enhance the stability of gel. The research results could guide the design and development of gels for conformance control in high-temperature and high-salinity reservoirs.