LECTURES ON GEOCHEMICAL !N1 ERPRETATION OF ...

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- 38 -and no silica scaling will occur in the separator as long as the p~ssureis maintained at or higher than 3.3 bars. Hote that if the solution pHincreases to as high as 8.5 as a result of CO partitioning into the steam2phase, the solution at point F would be about 125 mg/kg below saturation inrespect to the solubility of amo~hous silica (point L). and steam separationcould be carried out at a pressu~ as low as 2.25 bars (point G) withoutsilica sealing.C<strong>ON</strong>CLUSI<strong>ON</strong>SEquations are presented here that allow calculation of the solubilityof quartz at any temperature and pressure of geologic interest, and in anysaline solution (except Ha so.- rich solutions that complex dissolved2silica), provided the solution density is known at the temperature andpressure of interest. It is recommended that equation (7) be used forsilica (quartz) geothermometry. Equation (3) should be used for silica(chalcedony) geothermometry, and equation (19) should be used to calculatethe solubility of amorphous silica at the vapor pressure of the solution.Enthalpy- silica diagrams (or computer programs based on enthalpy- silicarelations) should be used to take account of the effects of boiling andmixing of different waters, and to calculate scaling potentials. Incalculating silica scaling potentials, account must be taken of thepossible increases in pH resulting from partitioning of CO into the2steam phase.
- 39 -REFERENCESA~o~sson, S., 1985, Gas pressure in geotherroal systems: Cbem. Geol., 49.p . 319- 328.Fournier, R. 0., 1973, Silica in the~l waters: Laboratory and fieldinvestigations, in Proceedings, International symposium on Hydrogeochemistryand Biogeochemist~. Tokyo, 1970 , v . 1. Hydrogeoehemistry:Washington, D.e., Clark. pp. 122- 139.Fournier. R.O. , 1977, Chemical geothc~ometers and mixing models forgeothermal systems: Geothennics, 5, 41- 50.Fournier. R.O., 1983, A method of calculating quartz solubilities inaqueous sodium chloride solutions: Geochim. Cosmochim. Acta . , 47,579- 586.Fournier. R. O. and Marshall, W. Lot 1983, Cal culation of amorphous silicasolubilities at 25° to 300·C and apparent cation hydration numbers inaqueous salt solutions using the concept of effective density of water:Geochim. cosmochim. Acta, 47, 587- 596.Fournier, R.O. and Potter, R.W., 11, 1982a, An equation correlating thesolubility of quartz in water from 25° to 900°C at pressures up to10,000 bars: Geochim. cosmochim. Acta., 46, 1969- 1974.Fournicr, R. O. and Potter, R. W., 11, 1982b, A revised and expandedsilica (quartz) geothermometer: Geotherm. Resourc. Counc . Bull . ,11(10), 3- 12.Fournier, R. O. and Rowe, J.J., 1966. Estimation of underground temperaturesfrom the silica content of water from hot springs and wet- steam wells:Am. J. Sci., 264.685- 697.Morey, C.W., Fournicr. R.O . and Rowe, J.J. , 1962, The solubility of quartzin water in the temperature interval from 25° to 300°C: Geochim.Cosmochim. Acta. 26, 1029- 1043 .Rimstidt, J . D., and Barnes, H.L., 1980, The kinetics of silica-waterreaction: Geochim. cosmochim. Acta, 44, 1683- 1699.
Page 1 and 2: ,. ,O~KUSTOFNUNNATIONAL ENER GY AUT
Page 3 and 4: PREFACESince the foundation of the
Page 5 and 6: P~eTHE SOLUBILITY OF SILICA IV HYDR
Page 7: - 1 -CARBONATE TRANSPORT AND DEPOSI
Page 10 and 11: - 4ca~bonic acid (Table 3). Equatio
Page 12 and 13: - 6 -Values of y a~ewater and the r
Page 14 and 15: - 8 -The s implest equation ~ep~ese
Page 16 and 17: - 10 -c0"0"'0>,'"0>>-.- .D"0"'Q)Q'"
Page 18 and 19: - 12 -The effect of partitioning of
Page 20 and 21: - 14 -FIGURE 5. The computed activi
Page 22 and 23: - 16 -REFEREYCESA~o~sson.S .• 191
Page 24 and 25: TABLE 2.Coefficients for use with e
Page 26 and 27: - 20 -TABLE 4. Values of ionie cnar
Page 28 and 29: - 22 -vapor pressure of pure water
Page 30 and 31: - 24 -Figure 2 shows the solubility
Page 32 and 33: - 26 -TABLE 2. Temperatures, enthal
Page 34 and 35: - 28 -800600~ci>E 400NoVi200o 500 1
Page 36 and 37: - 30 -800~ 600"- 0>E 400NoVi200o 50
Page 38 and 39: - 32 -has an enthalpy L , and the r
Page 40 and 41: - 34 -tempe~atu~e in kelvins. Molal
Page 42 and 43: - 36 -SILICA SCALING POT ENTIAL AS
Page 46 and 47: - 41 -CATION GEOTHERKOKETRYRobert O
Page 48 and 49: - 43 -fo~ dilute solutions). Thus,
Page 50 and 51: - 45 -3.002.50~ 2.00Q-;"1.50z~g-' 1
Page 52 and 53: - 47 -whe~e ~ is 1/3 fo~ wate~s equ
Page 54 and 55: - 49 -Kg concent~ations in geotherm
Page 56 and 57: - 51 -Na/l00070IMMATURE WATERSK/l00
Page 58 and 59: - 53 -CONCLUSIONSIn evaluating cati
Page 60 and 61: 55CONVECTION AS A MECHANISM FOR TRA
Page 62 and 63: 57and mainly wi thin interconnectin
Page 64 and 65: 59During drilling, the mud weight r
Page 66 and 67: 61TABLE 2. Calculation of specific
Page 68 and 69: 63REFERENCESG~iffiths.R.W., 1981. L
Page 70 and 71: 66Temperature __, t 1/
Page 72 and 73: 68crystallizing about 0.1 km 3 of r
Page 74 and 75: 70usually to the side along a ~ift
Page 76 and 77: 72Although the above calculations a

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