Study and Application of High Temperature Settling Stability of Cementing Slurry Used in Cementing Well Chuanshen-1

The well Chuanshen-1 is an ultra-deep exploratory well with completion depth of 8,420 m and bottom hole temperature of 178℃. The high temperature settling stability of the cement slurry is critical to the success of the cementing job. In laboratory experiment, the high temperature settling stability of a cement slurry was evaluated through HTHP thickening shutdown and measuring of the thickness of the settled particles on the bottom of the cement slurry cup. A technology of evaluating the high temperature stability of liquid organic polymer additive was developed using IR spectroscopy analysis and high temperature stability analysis of cement slurry. Using environmental scanning electron microscopy, the microstructure of cement slurry was studied, and the sizing of silica sands as well as the effects and mechanisms of ultra-fine micro sand, liquid silicon, nanophase SiO₂ and latex on the high temperature stability of cement slurry was investigated. The settling of cement slurries with densities between 1.90 g/cm³ and 2.30 g/cm³ at 150℃- 180℃ can be controlled using the technology studied. The technology has been applied in designing the cement slurry for cementing the 5th interval tubing string of the well Chuanshen-1. The high temperature stability of the cement slurry was excellent and the rate of excellence of the cement job was 88.1%.