Development and Performance Evaluation of Ultralow-Temperature-Resistant Plugging Agent for Antarctic Drilling

Summary In the process of Antarctic drilling, leakage of drilling fluid along microcracks in the ice layer, rock layer, and ice-rock interlayer can lead to wellbore instability and even collapse, which is currently the most common and damaging accident in Antarctic drilling. Adding plugging agents to the drilling fluid for plugging while drilling is an effective solution to address this issue. However, existing solid particle plugging agents are difficult to disperse and effectively suspend in low-temperature drilling base fluids, and conventional emulsion-based plugging agents cause a dramatic increase in the viscosity of low-temperature drilling fluid. Currently, there is no plugging agent suitable for Antarctic low-temperature drilling fluid, which severely restricts the progress of Antarctic drilling. For this study, we developed a new ultralow-temperature-resistant plugging agent [poly(amide-imide) PAI] with oil-in-oil emulsion polymerization for Antarctic drilling. A low-temperature kinematic viscometer, low-temperature dynamic particle size tester, low-temperature sand bed plugging test device, and low-temperature sand disc plugging test device were set up to systematically evaluate the performance of the plugging agent and its impact on the drilling fluid under ultralow-temperature conditions in situ. The performance was compared with that of commonly used plugging agents. Experimental results show that PAI can be well-dispersed and suspended in low-temperature drilling base fluids under ultralow-temperature conditions with minimal impact on the viscosity of the drilling fluid. Drilling fluids containing PAI show an invasion depth of only 2.9 cm for 160–300 mesh sandbeds after 30 minutes at −55°C, and the filtrate mass passing through a 5-μm average particle size sand disc at 500-psi differential pressure over 30 minutes is only 2.73 g, offering promising support for safe and efficient drilling under Antarctic ultralow-temperature conditions.