Development and Performance Evaluation of Deepwater Enzyme-Responsive Temporary Plugging Agent

Deepwater oil and gas resources are abundant, and their development has become an important pillar of energy supply. However, deepwater drilling presents considerable challenges due to the complex geological conditions, wherein mass transfer interactions between drilling fluids and shallow formations result in a reduction in reservoir permeability. These conditions contribute to significant issues such as borehole instability and reservoir damage during drilling operations. This study proposes an enzyme-responsive temporary plugging agent, which utilizes cross-linked chitosan and starch to encapsulate modified ceramic particles. The microcapsules exhibit high mechanical strength during drilling and demonstrate excellent sealing capabilities. Under the influence of biological enzymes, the chitosan material undergoes degradation, thereby restoring reservoir permeability. The particle size of the temporary plugging agent is typically 30 μm, and thermogravimetric analysis reveals that decomposition begins at 203 °C. After 24 h of degradation at 90 °C in the presence of amylase, the permeability recovery rate of the temporary plugging agent reaches 75.18%. As degradation time increases, the permeability recovery rate improves progressively. The enzyme-responsive temporary plugging agent establishes an “isolation barrier” around the borehole, effectively preventing the interaction between the wellbore and the formation during drilling. Upon completion of drilling, the biological enzyme degradation of the plug facilitates the reopening of flow paths around the wellbore. The temporary plug effectively addresses the challenges of wellbore instability and reservoir protection, playing a crucial role in deepwater oil and gas extraction.