Gel Breaking Affecting Factors Analysis on Polymer Bio-Degradation

Recent years have witnessed a renewed interest in the development of coalbed methane (CBM) reservoirs. However, horizontal drilling in unconsolidated and soft coal seam for CBM drainage and exploitation often results in wellbore instability. This paper proposed degradable drilling fluid in CBM horizontal drilling which not only can maintain wellbore stability, but also minimize formation damages caused by drilling fluid. Its factors of gel breaking ratio were systematically studied from the aspects as substrate concentration, pH, temperature, enzyme concentration and reaction time. We found that in a condition when enzyme concentration is abundant, increasing of substrate concentration would result in higher gel breaking ratio. Furthermore, nearly neutral pH (pH≈7), moderate temperature (40°C~60°C), enzyme with higher concentration and longer action time (more than 3 hours) could enhance gel breaking ratio.