Preparation of active MgO composite expansive agent and its effect on volume deformation performance of cement slurry during hydration

ABSTRACT

The serious volume shrinkage of G-grade oil well cement during the hydration period and the initial stage of hardening will cause poor cementing quality at the first and second cementing interfaces, which will lead to annulus channeling and ultimately affect the normal production of the oil well. Therefore, we researched high-activity MgO composite expansive agent. By calcination of industrial MgO at different temperatures and then rapid cooling, we obtained MgO with different activities. We then analyzed the reactivity and microstructure of these samples and tested their effects on the volume shrinkage of cement slurry in the early stage of hydration. The experimental results showed that the activity of the sample calcined at 800°C for 1 hour then cooled rapidly is more suitable. After adding the expansive agent, the volume shrinkage rate of cement slurry can be minimized to only 0.95% after 10 hours, while the volume shrinkage rate of blank cement slurry can reach 4.02% after 10 hours. By compounding the calcined active MgO with CaO and UEA, the composite expansive agent M-AC is obtained. The evaluation results showed that M-AC expansive agent can make up for the insufficient expansion of cement after hardening, realize the volume shrinkage compensation of cement in the whole process of cementing, and improve the cementing quality.

KEYWORDS:

• Magnesium oxide
• calcination
• rapid cooling
• activity
• crystal deficiency
• expansion

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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Notes on contributors

Zhi-Gang Peng

Zhigang Peng, Doctor, College of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu, Sichuan, China.

Xiao-Feng Zhang

Xiaofeng Zhang, Master, College of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu, Sichuan, China.

Qian Feng

Qian Feng, Doctor, College of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu, Sichuan, China.

Yong Zheng

Yong Zheng, Doctor, College of Chemistry and Chemical Engineering, Southwest Petroleum University, Chengdu, Sichuan, China.