SUPCRT98(修正版SUPCRT92)の熱力学データセットの信頼性
地熱系における鉱物飽和度指数計算による検証
2004 年 54 巻 1 号 p. 47-60
詳細
2004 年 54 巻 1 号 p. 47-60
The reliability of the thermodynamic dataset of SUPCRT98 (revised SUPCRT92, Johnson et al., 1992) was checked by calculating mineral saturation indices for geothermal waters. For comparison, the calculation was also conducted using the thermodynamic dataset of SOLVEQ86 (revised SOLVEQ, Reed, 1982). New computer code (GEOMS) was written using Visual Basic (ver.6.0). In order to calculate the mineral saturation indices, mass-balance equations and mass-action equations are solved in a successive iteration method. Total ionizable hydrogen ion (TOTH) was used as a mass balance for hydrogen ion.
Judging from the consistency of the calculation results with the field evidences, the dataset of SOLVEQ86 is considered to be unreliable in the temperature range of 170 to 300°C. On the other hand, the thermodynamic dataset.of SUPCRT98 was judged to be more reliable in the same temperature range. In the calculation of mineral saturation indices, attention should be paid to the aluminium concentration in geothermal waters because the aluminium concentration makes a large effect in the calculation results of mineral saturation indices.
