In　the　recent　decades,　the　merit　of　enhancing　drilling　rate　by　wellbore　gas　scavenging　has　been　described　comprehensively　in　many　papers.　This　method　began　to　be　used　widely　and　successfully　in　field　conditions.　In　comparison　with　air　and　natural　gas,　due　to　its　inertness　and　inflammability,　gaseous　nitrogen　has　become　the　most　preferred　fluid　for　drilling.　The　biggest　shortcoming　of　using　nitrogen　gas　as　drilling　fluid　is　high　cost　of　its　production.　If　the　nitrogen　gas　circulated　out　of　the　wellbore　could　be　recycled　by　some　ground-based　equipment　and　injected　into　the　wellbore　again,　nitrogen　gas　drilling　may　become　more　viable.　In　this　work,　we　developed　a　new　nitrogen　gas　circulation　drilling　technology　and　carried　out　a　systematic　study　of　the　proposed　project,　namely,　the　technological　process,　development　of　separation　equipment　and　control　system,　etc.　To　verify　the　feasibility　of　this　technological　system,　a　comprehensive　on-site　experiment　was　designed　and　implemented　for　testing　the　prototype　system.