High temperature water adsorption on The Geysers rocks

In order to measure water retention by geothermal reservoir rocks at the actual reservoir temperature, the ORNL high temperature isopiestic apparatus was adapted for adsorption measurements. The quality of water retained by rock samples taken from three different wells of The Geysers geothermal reservoir was measured at 150{sup degree}C, 200{sup degree}C, and 250{sup degree}C as a function of pressure in the range 0.00 {<=}p/p{sub degree} {<=} 0.98, where p{sub degree} is the saturated water vapor pressure. Both adsorption (increasing pressure) and desorption (decreasing pressure) runs were made in order to investigate the nature and the extent of the hysteresis. Additionally, low temperature gas adsorption analyses were performed on the same rock samples. Nitrogen or krypton adsorption and desorption isotherms at 77 K were used to obtain BET specific surface areas, pore volumes and their distributions with respect to pore sizes. Mercury intrusion porosimetry was also used to obtain similar information extending to very large pores (macropores). A correlation is sought between water adsorption, the surface properties, and the mineralogical and petrological characteristics of the solids