Evaluating sealability of blended smart polymer and fiber additive for geothermal drilling with the effect of fracture opening size

Geothermal formations often contain extensive fracture networks. These fracture networks contribute to the significant loss of drilling fluids during geothermal drilling. Multiple loss circulation materials (LCM) such as fiber, granules, and pills have been proposed to tackle this problem but with only limited success. Recent advances in materials science have led to the development of thermoset shape memory polymers (SMP) to address the lost circulation problem. In this paper, we evaluate a thermoset SMP performance in sealing near wellbore fractures of different sizes in geothermal wells. The SMP performance was assessed using granite disks and cylindrical granite cores having fracture sizes of 1000 mu m and 3000 mu m. A static filtration test was performed using cedar fiber, CaCO3, and SMP. Results showed cedar fiber performed better than the CaCO3., reducing fluid loss by 89% and improving sealing pressure by 200 psi. A novel dynamic testing unit that allows for high-temperature testing under flowing conditions was used in this study. The analysis showed that 3% by weight SMP and fiber blends could bridge and plug the 1000 mu m fracture. For a larger fracture of 3000 mu m width, there was a need to increase the weight concentration of the SMP to 6% to plug the fracture opening effectively. We showed the influence of key parameters such as the type of LCM, concentration, and particle size distribution in optimizing the performance of drilling fluid loss treatment.

Automated summary

The paper evaluates the performance of thermoset shape memory polymers in sealing near wellbore fractures of different sizes in geothermal wells, showing that a 3% by weight SMP and fiber blend can effectively plug a 1000 μm fracture. Increasing the weight concentration of the SMP to 6% is needed to plug a larger 3000 μm fracture. The study highlights the importance of key parameters such as type of loss circulation materials, concentration, and particle size distribution in optimizing the performance of drilling fluid loss treatment.