Preparation And Performance Evaluation Of Powder Type Silicone Defoamer For Cement Slurry

To improve the performance of cement admixture, cement slurry is add, some of it with high surface activity that can produce stable bubbles in the process of preparing and pumping cement admixture. At same time, cement slurry system contain a large amount of solid phase and a high consistency, thus gas bubble in plasma is difficult to be eliminated in a short period of time, which leads to the changes of performance parameters of cement slurry, and directly affects the quality of cementing, seriously, cause the failure of cementing. Therefore, in the preparation of cement slurry, agent must be add to eliminate the bubble and improve the cementing quality. Traditional emulsion and solution type agent has many drawbacks, so it is necessary to develop a new type defoaming agent which can overcome the disadvantages. According to the oil well cement slurry system, a kind of powder organic silicon foam removing agent with excellent performance, such as convenient use, safety, high stability and convenient transportation, is developed in this paper.To produce anti foam agent with best activity of eliminating bubble, the silicone paste, glycerin polyether and Span were mixed in the mass ratio of 60:31:9, and constantly stirred in 60℃. Hexamethyldisiloxane as silane coupling agent is used to modify the hydrophobic of the surface of diatomite and improve spreading ability of diatomite in the water level. Through the orthogonal experiment and single factor experiment, the modified conditions of diatomite is optimized. The experimental results show that:when 500 mesh diatomite is used, the amount of hexamethyl disiloxan is 5% of the quality of diatomite, and heating in 110℃ for 2h, the modified diatomite has the best hydrophobic properties. To produce S2-A type powder defoamer, modified diatomite and defoaming agent active substance are mixed in the mass ratio of 60:40, stirring constantly, heating in 60℃ for lh, which make the defoaming agent active substance uniformly adsorp and adhes on the surface of diatomite. The results of powder defoaming agent performance evaluation show that:when the dosage of S2-A type powder defoamer is 0.5% of the quality of the cement, cement slurry density recovery rate reached more than 90%, which shows the excellent defoaming performance; the addition of powder defoaming agent has no adverse effects on cement paste fluidity, thickening time, rheology and cement stone strength.