Upton, NY - The U.S. Department of Energy's Brookhaven National Laboratory has developed a new high-performance cement for use in geothermal wells, which pump hot water or steam from the interior of the Earth to drive electricity-generating turbines. The cement is also particularly suited for use in oil wells and for soil remediation.
About two percent of the world's electricity is derived from geothermal energy. In geothermal environments, an abundance of carbon dioxide causes conventional cement to deteriorate rapidly through a chemical process called carbonation. In contrast, the high-efficiency cement creates a zeolite mineral and a calcium phosphate mineral that block this destructive chemical reaction.
The formula for the cement includes fly ash, calcium aluminate, sodium polyphosphate and water in compositions that vary with the depth at which the cement will be used. Since these materials are abundant and inexpensive, and no technical training is required to make the cement, it is economical compared to conventional cements.
In laboratory tests, when the Brookhaven cement had been exposed for six months to steam as hot as 572oF, with a concentration of four percent carbon dioxide, the high-performance cement became only one percent carbonated, while conventional cement was ready to crumble, with 50 percent carbonation.
In July 1997, large-scale field testing of the Brookhaven cement began at a geothermal well in Sumatra, Indonesia, operated by Unocal Corporation of Sugar Land, Texas. Halliburton Energy Services, of Duncan, Oklahoma, is supplying the cement for these tests.
Brookhaven Lab chemist Toshifumi Sugama, who developed the cement, said, "This high-performance cement is not only resistant to the deterioration produced by carbon dioxide, but it also adheres well to steel and soil, protects steel from corrosion, has high mechanical strength, low permeability and withstands temperature extremes. It is environmentally friendly because it is made mostly of recylced fly ash - the byproduct of steel production - and no harsh chemicals are used in manufacturing it. Besides using the cement in specialized environments, it can also be used in walkways, roads, and buildings - anywhere ordinary cement is used."
Brookhaven National Laboratory carries out basic and applied research in the physical, biomedical and environmental sciences and in selected energy technologies. The Laboratory is operated by Associated Universities, Inc., a nonprofit research management organization, under contract with the U.S. Department of Energy.
NOTE TO LOCAL EDITORS: Toshifumi Sugama is a resident of Wading River, NY.