LAUSR

The rapidly increasing global oil/gas demand and gradual depletion of shallow reservoirs require the development of deep oil/gas reservoirs and geothermal reservoirs. However, deep drilling suffers from drilling-fluid failures under ultrahigh temperature, which cause serious accidents such as wellbore collapse, stuck pipe, and even blowouts. In this study, we revealed the role of polymeric additives in improving the ultrahigh-temperature tolerance of bentonite-based drilling fluids, aiming to provide practical and efficient solutions to the failure of drilling fluids in severe conditions. By adding poly(sodium 4-styrenesulfonate) (PSS) to the original drilling fluid containing bentonite, significant fluid loss—as a consequence of bentonite-particle flocculation causing drilling-fluid shear-stress reduction and high-permeability mud—is successfully suppressed even at temperature as high as 200°C. This drilling fluid containing PSS was applied in the drilling of high-temperature deep wells in Xinjiang province, China, and exhibited high effectiveness in controlling accidents including overflow and leakage. NOTE: A supplementary file is available in the Supporting Information section.