| 摘要 |
Particulate magnesium oxide prepared by calcining magnesium oxide at between about 1100.degree.C and about 1500.degree.C. At least about 80% of the magnesium oxide particles are between about 150 microns to about 400 microns in diamater. This magnesium oxide is capable of producing expansion in set cements when the temeperature thereof is at least about 60.degree.C. Preferably the magnesium oxide has been calcined at between about 1100.degree.C to about 1300.degree.C for about 1 to about 3 hours, and at least about 80% of the particles are between about 200 microns to about 325 microns. Further, the BET surface area of the particles is preferably between about 0.8 to about 1.8 m2/g, and the acid neutralization time (using the method described) is between about 15 to 20 minutes, and further preferably between about 17 to about 25 minutes. Expandable cement compositions using such magnesium oxide, and a method for using them in cementing of wells, are also disclosed. |
