MULLITE MICROSPHERE-FILLED LIGHTWEIGHT CALCIUM-PHOSPHATE CEMENT SLURRIES FOR GEOTHERMAL WELLS - SETTING AND PROPERTIES

The chemical factors affecting the setting properties of microsphere-f illed lightweight calcium phosphate cement (LCPC) slurries, ranging in density from 1.32 to 1.12 g/cc, at high hydrothermal temperature were investigated. The LCPC slurries consisted of calcium aluminate cement (CAC) as the base reactant, a -(-NaPO3-)-(n) solution as the acid rea ctant, and mullite-shelled hollow microspheres as the lightweight addi tive. Two major aspects were studied; one was the importance of the ch emical constituents of CAC, and the other was the rate of the hydrothe rmal reaction between the mullite shell and the Na ions dissociated fr om -(-NaPO3-)-(n). For the former, the use of CAC having C(2)AS and CA phases as the major chemical components shortened the thickening time of LCPC slurries, whereas CACs with CA, CA(2), and alpha-Al2O3 phase components extended the thickening time. For the hydrothermal reaction , an excess of zeolite X type formed by the uptake of Na by mullite mi crospheres reduced the thickening time.