Preliminary Study on Air Injection in Annuli to Manage Pressure during Cementing

Along with the development of low permeability reservoirs, underbalanced drilling technology is applied more and more widely. During the cementing operation of underbalanced drilling wells, cementing liquid can flow into the reservoir more easily for the absence of the mud cake, which certainly weakens the reservoir protection advantage of underbalanced drilling. Based on the methods of underbalanced drilling and managed pressure drilling, a new method of cement technology, Balanced Pressure Cementing Technology by Air Injection in Annuli, was put forward. The calculation models of the maximum depth of injection point and the maximum start-up pressure were built. Considering the power limitation of the pump, valves of gas lift were introduced and the calculation method of valve location was developed. This technology could effectively control the annulus pressure of wellbore, assure the cementing quality and protect the hydrocarbon reservoir, thus reduces the exploration and development cost.