Patent ID: 9404328
Filing Date: 2016-08-02
CPC Classification: E21B

Claim Text:
1. A method for injecting gas into a drilling annulus surrounding a drillstring during a drilling process for drilling a borehole into a subterranean formation, where the drilling annulus comprises an annular space between the drillstring string and a casing string and the drillstring extends from a surface location down the borehole, the method comprising: pumping gas into the drilling annulus, wherein the gas is pumped into an injection pipe and through a set of one or more gas injection ports into the drilling annulus, and wherein the set of one or more gas injection ports are in fluid communication with the gas injection pipe and the drilling annulus; flowing drilling fluids between the drilling annulus and the gas injection pipe through a set of one or more flow ports, wherein the set of one or more flow ports are in fluid communication with the gas injection pipe and the drilling annulus, and wherein the set of one or more flow ports are a vertical distance below the set of one or more gas injection ports such that the set of gas injection ports are located between the set of one or more flow ports and the surface location; and using a hydrostatic head of a column of drilling fluids extending between the set of one or more flow ports and the set of one or more gas injection ports to seal the set of one or more flow ports when gas is flowing from the drilling pipe through the set of one or more gas injection ports into the drilling annulus.