Abstract: Low-pressure formations susceptible to circulation lost in ultra-long cementing intervals are characterized by high displacing pressures,high cementing risks,frequent lost circulation,pump choking and other problems.Under such circumstances,an innovative low-density cement lightening material,SXJ-1,has been developed and applied in the fields.Through condensation polymerization,modified epoxy can be generated and be used in combination with active SiO2,curative agent and other materials to generate low-density cement lightening material,SXJ-1.With SXJ-1 as the lightening material and in accordance with the theory of close packing,setting accelerator XC-1 and the composite reinforcing material,XE60S with hydrate activity have been used to prepare low-density cement slurry with densities of 1.3-1.5 kg/L composed of solid beads.In the subject study,the basic performances of the cement slurry were evaluated along with the impact of pressures and agitation speeds on densities.Assessment tests resulted in outstanding primary performance with the cement slurry.Densities of the slurry may vary with changes in pressures and agitation speeds,but the fluctuations can be controlled within 0.03 kg/L. With no significant changes in performances,Further,these slurries displayed outstanding pressure-bearing and anti-shearing capacities.SEM tests showed that the cement concretions formed by the slurry have high bond integrity,with tight structures showing no obvious cracking or water seepage.Generally speaking,the material can effectively promote overall performances of the cement concretions.Prepared cement slurry has been applied in over 30 wells in Shengli Oilfield.Cement returned to wellhead in one trip with success rate of 100% for all these wells.Research results showed that the innovative low-density cement lightening material,SXJ-1,possesses outstanding pressure-bearing and anti-shearing capacities.The low-density cement slurry composed by solid beads prepared by the lightening material can effectively meet the challenges in cementing operations in low-pressure cementing intervals susceptible to lost circulation.