Tabnak gas field is located in the Fars province, Southern Iran. Severe lost circulation problem were encountered while drilling the long interval of large size hole in the highly fractured and porous carbonate formations. To resolve the severe lost circulation problem, Air and air/foam drilling technology was chosen as a main means to drill through the top intervals and an air/foam drilling program was worked out. The field application proved that air and air/foam drilling could resolve the severe lost circulation problem in the highly fractured and porous carbonate formations with very low formation pressure and speed up the penetration rate significantly. The drilling cost also reduced dramatically.