Synthesis of an amphoteric polymer as a high‐temperature‐resistant shale stabilizer in water‐based drilling fluids

To meet the increasing requirement of stabilizing shale under high‐temperature situation with the use of water‐based drilling fluids (WBDFs), the high‐performance shale stabilizer is an urgent need. In this study, an amphoteric copolymer of AM/DMDAAC/NVP (APC) was synthesized by acrylamide (AM), dimethyl diallyl ammonium chloride (DMDAAC), and N ‐vinylpyrrolidone (NVP) and used as a high temperature‐resistant shale stabilizer. The Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy confirmed the successful synthesis of APC. The inhibitive performance of APC was systematically evaluated and compared with three other commonly used shale stabilizers, including the anionic potassium polyacrylamide (KPAM), cationic poly dimethyl diallyl ammonium chloride (PD), and amphoteric polymer FA367. The results demonstrated that APC displayed excellent performance on the linear swelling test, hot‐rolling recovery experiment, and shale immersion test. Furthermore, APC combined the advantages of high shale recovery percentages of PD and maintaining shale pellet integrity of KPAM, avoiding the drawbacks of enormous filtration volume of PD and low shale recovery percentages of KPAM. These great properties indicated that APC would be suitable as a shale stabilizer in WBDF to drill high‐temperature shale formation.