Abstract: Hollow microspheres-nitrogen foam cementing technology with ultra-low density could potentially solve the problem of cementing leakage in Hangjinqi Block.It could also assure the one-trip safe return of cement slurry to form a complete cement sheath,and the improve the cementing quality and wellbore integrity.An ultra-low density hollow microspheres-nitrogen foamed slurry with a density of 1.15-1.20 kg/L wad developed by charging nitrogen into the low-density hollow microspheres slurry system,and adding foaming agent and foam stabilizer to form a high-pressure nitrogen-charged foaming technique.The matching field choking and back pressure devices were combined with independently designed and developed mechanical nitrogen injection equipment.By doing so,the foamed cementing slurry technology with ultra-low density for pressure management and leakage control was established.The technology has been used to cement the technical casing in 5 wells in Hangjinqi Block,and in each,the slurry was safely returned one time.The average density of downhole hollow microspheres-nitrogen foamed slurry in Well JPH351 is 1.15 kg/L,the length of cemented section is 2 800.00 m,and both have excellent cementing quality.The successful development and application of ultra-low density hollow microspheres-nitrogen foamed cementing slurry technology has provided a new technical approach for addressing cementing leakage problem of low pressure wells in Hangjinqi Block and similar blocks.