Cement slurry optimization for ultra-deep directional well in Moxi-Gaoshiti structure

Liner cementing engineer is faced with problem of poor cementing quality in lower part of Moxi-Gaoshiti structure, which has features of lower displacement efficiency of deviated and horizontal wells with an average of 92.7%; gas invasion occurs easily during waiting on cemented due to long sealing section of liner and small annulus clearance; the compatibility of density and rheology of drilling fluid, isolation fluid and cement slurry is poor; the upper well section is active and prone to oil-gas-water channeling which leads to gas-water invasion challenges. In this paper, based on the engineering geological characteristics of the area, the wide temperate retarder and high temperature water reducing agent are optimized, which have high temperature, high pressure and large temperature difference under the condition of gas reservoirs development, and on this basis, the anti-channeling cement slurry system is developed, which is suitable for high temperature and high pressure and large temperature difference conditions. The slurry compressive strength can reach more than 14 MPa to 29.5 MPa by curing within 24 h under 165 ℃ and 65 ℃, and at the same time, the slurry has good anti-temperature stability and anti-channeling performance under large temperature difference. The slurry can also effectively prevent the gas channeling under the condition of good cementing quality (formation pressure gradient is less than 2.0). After field application, the rate of excellent and good cementing quality has increases by approximate 30%, and the rate of qualified evaluation increases by more than 50%. The high temperature, high density and large temperature difference anti-channeling cement slurry can significantly improve sealing quality of liner casing in the Moxi-Gaoshiti area, which provided guarantee for the safe, economical and efficient development of Longwangmiao gas field.