Development of a dual-functional inhibitor for natural gas hydrates and construction of drilling fluid system

Throughout the 21st century, natural gas hydrates have emerged as a pivotal and promising clean energy resource with immense potential for commercial development. However, during shallow-water gas hydrate drilling in deep-sea areas, heat and mass transfer between the drilling fluid and the natural gas hydrate reservoir result in hydrate dissociation. As a result, the reservoir strength is weakened, wellbore instability occurs, and there is a high risk of well collapse. Additionally, the formation of secondary hydrates can cause blockages in drilling tools or pipelines, compromising drilling safety. In this study, acrylamide and dimethyl diallyl ammonium chloride were used as raw materials to successfully develop a dual-effect hydrate inhibitor named ADP. The results showed that a 1% ADP concentration increased the inhibition efficiency of hydrate dissociation by approximately 21.13%. Furthermore, core immersion and linear expansion experiments using a 1% ADP solution showed that after 24 h, the core maintained its structural integrity without experiencing collapse, and the linear expansion rate decreased to 1.5%. Building upon the HEM system, this research employed the developed dualeffect hydrate inhibitor as the core component and further optimized density, rheology, filtration loss, hydration expansion inhibition, and hydrate inhibition properties to construct a high-performance water-based drilling fluid system for strong hydrate inhibition. Performance evaluation of the HTX system demonstrated excellent rheological filtration, lubrication, plugging, hydration expansion inhibition, and hydrate inhibition properties. Additionally, predictive models for drilling fluid rheological parameters under different temperature conditions were established. The research outcomes presented in this paper hold significant practical value in addressing the wellbore stability issues encountered during the drilling process of gas hydrate reservoirs in deep-sea areas.