Two-stage Cementing Technology for Production Casing in Deep Reservoir of Chenghai Oilfield

Abstract The whole well section cementing of production casing in 5 000 m deep reservoir of Chenghai Oilfield was faced with many difficulties, such as long sealing section, large temperature difference, serious leakage and serious cement slurry contamination caused by organic salt drilling fluid. On the basis of the stage cementing technology, the newly developed micro thixotropic cement slurry and anti-organic salt spacer were used to reduce leakage and contamination, and the double-acting stage collar was applied to reduce the risk of stage cementing tool failure. A two-stage cementing technology suitable for the development of deep reservoir in Chenghai Oilfield was formed. The cement slurry exhibits good micro thixotropic performance at 50~130 °C. The rheological properties change from thin to thick and then to thin with increasing temperature, and the difference of static shear force is no less than 12.2 Pa. The spacer shows good anti-contamination property. The thickening time of the contaminated cement slurry after mixing the spacer is more than 6 h, and the sedimentation stability of the spacer is no more than 0.04 g/cm 3 . The double-acting stage collar has the advantages of both mechanical and differential pressure stage collar, which can effectively reduce the risk of circulation holes not being opened or closed. The technology had been successfully applied in 2 wells in Chenghai Oilfield. During cementing operation, the stage collar worked well, there was no leakage, cement slurry contamination could be controlled, and cementing quality met needs. The technology can be further promoted and applied in the area.