| Abstract |
The chemical equilibrium software that is available for geothermal studies has traditionally remained cumbersome in application, due to complex data input and output formats and the limitations of character-based computer operating systems. To address this limitation, the WATCH computer code, which calculates composition, aqueous speciation and mineral saturation in geothermal reservoir waters, has been upgraded and transferred to MS-Windowsô (Windows 3.1, Windows 95 or Windows 98), under the name WatchWorks. Program input consists of water and gas/steam or dissolved gas analyses, which are used with temperature or pressure and total flow enthalpy to calculate the reservoir fluid composition at conditions specified by geothermometers or by input. An extensive variety of data units is accepted, including for waters (mg/kg solution, mg/l solution, mg/kg H2O, mmoles/l solution and mmoles/kg H2O) and for gases in steam a total of 10 different composition bases (including mg, mmoles, mole%, wt.% and ppm-wt all including H2O; vol.% dry gas with liters of total gas per kg of H2O, and; vol.% residual gas with mg or mmoles acid gases per kg H2O). Temperature may be in ?C or ?F, pressure in bar, ksc, psi or MPa, enthalpy in Joules, Calories or BTU. Data already entered can be instantly converted (on-screen) to alternate units. The temperature range of calculations is 0? - 370?C. Program output includes pH, redox potential, the partial pressures of dissolved gases, reservoir steam fraction and composition, activity coefficients, ionic strength and theoretical and calculated mineral solubilities. Up to ten steps of boiling or cooling/heating may be specified, and output of boiling or cooling may be re-directed to input. WatchWorks assists analyses of analytical data at laboratory temperature, reservoir temperature and mineral saturation, scaling and corrosion potential, effects of boiling and cooling, and excess steam in the wellflow with respect to measured enthalpy or enthalpy calculated from chemical geothermometers. The amount of acid, base or CO2 gas needed to adjust brine pH can be calculated, as may be needed to inhibit scale formation and/or neutralize a low pH. The Windows environment provides for extensive input-output control, including tabulation of the output from successive boiling and cooling steps. Some refinements of the underlying WATCH thermodynamic code have been included, to improve the handling of very high temperature and/or excess steam, and to expand the output to include additional geothermometers and carbonate species information. Examples of applications are provided. |