| 摘要 |
<p>A cement composition comprising a mixture of: (i) an hydraulic cement; and (ii) one or more additives that contribute Si, Ca or Al to the mixture; has a mineralogical composition within the margarite-quartz-pectolite region of the Si-Ca-Al phase diagram. The constituents are selected to optimise the formation of anorthite when the cement is used in high temperature oil, gas, water or geothermal wells. Anorthite provides a strong and durable matrix at these temperatures (250 to 400{C). For 100 parts of cement, the additives may include 11.5-80 parts silica, 28-143 parts kaolin / metakaolin and 14.8-72 parts fly ash. Preferably the average particles size of the kaolin / metakaolin is 2 to 10žm, of silica is 2 to 330žm, and of fly ash is 50-400žm.</p> |
