Research on foam drilling fluid and its application

Analysis on reservoir protection mechanism of foam drilling fluid and relation between its performance and temperature, pressure, time and all ingredients reveals that foam drilling fluid has good lost circulation control and plugging ability, and good cleaning efficiency; especially in high-inclination well and/or horizontal wells, it clears off the cutting beds settled at the lower side of the borehole.Field using indicates that foam drilling fluid is suitable for drilling the formations with fracture developing, severe leakage, low pressure and ultra-low pressure problems, and can satisfy the requirements of logging and formation protection.The drilling fluid also has such advantages as stable property, low hydrostatic fluid column pressure, good lubrication and cuttings transportation capacity, little filtrate loss and friction loss, strong resistance to contamination, and little damage to formation, etc..With the using of the foam drilling fluid, accidents can be effectively reduced and well sloughing can be prevented remarkably.It is very useful in drilling low pressure low permeable formation and high-inclination and horizontal sections.