Air drilling technology using of aerated foam

For those wells with reservoir and formation pressure coefficients less than 1, such techniques as aeration, foam drilling and air drilling are usually adopted both for drilling and workover, so as to reduce the pressure in the hole and reach the goals of reservoir protection and lost circulation prevention. Diesel engine residue gas is applied for drilling the production zone to prevent downhole explosion. Testing and field using show that the aerated foam drilling technology can be used to develop the low-pressured oil and gas wells and the depleted wells with pressure coefficients of 1. 0-0. 3, thus broaden the range of oil and gas development and effectively protect the reservoirs. For some lost circulation wells in the pressure coef- ficient range, the foam and air drilling technology can achieve the remarkable effects which are impossible for the conventional drilling fluid and plugging technologies, thus shortens the drilling period and reduces the comprehensive drilling cost of the lost circulation wells.