Experimental investigation of PAM/PEI polymer mud for reducing lost circulation in high-temperature formations

Abstract

Lost circulation is a common and costly problem, especially in high-temperature oil and geothermal wells. Lost circulation materials, including polymeric solutions, are often used to remediate the problem. This study considers using thermoset polymeric gels in water-based drilling fluids as lost circulation materials (LCM) to mitigate the circulation loss in oil and geothermal wells at high temperatures of 150°C (302°F). Two polymers were considered, polyacrylamide (PAM), which serves as the base gel, and polyethyleneimine (PEI), an organic crosslinker. The rheological and sealing property of the PAM/PEI combination as lost circulation material was examined at 150°C (302°F) using a high temperature and high-pressure rheometer and a permeability plugging tester. The results showed the optimum gelation of the mud at 6% PAM and 1.25% PEI solution occurred at 17 minutes. The polymer mud tends to form an elastic-like solid at high concentrations of PAM and PEI. The PAM/PEI polymer mud reduced the fluid loss by 80% during the sealing treatment compared to the conventional LCM treatments with water-based mud. Also, details on effective mixing procedure and testing technique using 3D-printed tapered fracture discs are presented.