Foam drilling fluid technology in TABNAK gas field, Iran

Air/foam drilling fluid systems have been used in TABNAK gas field of Iran to solve the problems of fracture developing, formation communication and lost circulation during drilling in low pressure fractured carbonate formation. The drilling fluid systems include dust, mist, stable foam and foam drilling fluids. The air/foam drilling fluid has such properties as low air/fluid column pressure, high ROP, lost circulation prevention, etc. , and gypsum and high concentration saline contamination resistance. Foaming agent and foam formulation of large foaming volume, long stabilization period, salt and calcium resistance, high temperature tolerance have been optimized based on experiments, and field using showed that the air/foam drilling fluid systems are suitable for using in the low pressured dry formation and water zone, it needs low air pumping rate and higher salt and calcium resistance; it has low density, good cuttings transportation and suitable for fast drilling through the thief formation. By using the air/foam drilling fluid, ROP of 25 m/h was achieved, and the average ROP is 3-5 times of the conventional drilling.