Abstract:As the depth of the well increasing in our oil and gas field development, the well control is more and more important. Conventional well killing methods, such as driller’s method and engineer’s method, are usually applied in dealing with overflow, but these methods may cause a high surface casing pressure, which may exceed the safe range of equipments and lead to an accident. Reverse circulation well killing method is an unconventional well control method that pumps killing fluids through the annulus and excludes the overflow from drill string. This paper based on previous studies deduces the initial killing displacement calculation method to prevent gas channeling. Considering the great difference between annulus friction and drill string friction, this paper decides a security added value for circulating pressure in the processing of killing well according to field experience and deduces the mathematical model of the circulation pressure and stand pipe pressure in the processing of reverse circulation well killing based on gas state equation, and analyzes the trend of circulation pressure and annulus pressure in killing well. Finally, complied a calculation program. According to the result of example, this program is proofed to be correct and can be applied in the calculation of reverse circulation well killing method.