Synthesis and Inhibition Mechanism Research of Polyampholyte Shale Inhibitor

In order to improve the inhibition of water-based drilling fluid and solve the problems such as instability and collapse of borehole caused by drilling in shale formation, this study developed a kind of polyampholyte inhibitor. In this study, the performance of polyampholyte inhibitor DAM was evaluated through tests of hot-rolling dispersion, linear swelling, bentonite inhibition and resistance to temperature. The inhibitive mechanism of DAM was analyzed through zeta potential measurement, water activity test, scanning electron microscopy and X-ray diffraction analysis. The results indicated that DAM could inhibit shale hydration and dispersion effectively, and showed good synergetic effect when used together with 3% KCL, and it could perform well in solution under high temperatures up to 140℃. Comprehensive integration of X-ray diffraction, zeta potential techniques, water activity test and SEM helped identify the inhibition mechanism. The five-membered ring formed in the DMDAAC molecular chain not only had strong inhibitory performance, but also had good resistance to temperature. -SO3Na enhanced the salt resistance of the molecule, while -OH contributes to the formation of DAM hydrated film on the clay surface. Low molecular weight and linear characteristics of DAM enabled itself to enter the clay layer more easily to enhance the inhibition performance.