Geothermal reservoir

N. E. V. Rodrigues, B. A. Robinson, and E. Counce, "Tracer Experiment Results During the Long-Term Flow Test of the Fenton Hill Reservoir", Proceedings of the Eighteenth Workshop on Geothermal Reservoir Engineering Stanford University, Stanford, Calif., 1994, in press. 

In the primary binary loop, production wells recover 170°C hot water from the geothermal reservoir and deliver 3,036 m /lir at 14 bar to heat exchangers in the power plant. Water leaves the heat exchangers at 70-90°C and is recycled to the ground through a re-injection well at a depth of 400-600 m. In the secondary binary loop, the heat from the hot water evaporates the isobutane working fluid at 36 bar and 150°C (Table 4-2). 

Fouillac, C. and Michard, G. (1981) Sodium/lithium ratio in water applied to geothermometry of geothermal reservoirs. Geothermics, 10, 55-70. 

Battistelli A., Calore C., et al. The simulator TOUGH2/EWASG for modeling geothermal reservoirs with brines and non-condensible gases. 1997 Geothermics 26(4) 437-464. 

The utilization of geothermal reservoirs involves drilling and extraction of fluid from the reservoir at a rate, which usually far exceeds the natural discharge rate. Often, hot water in... 

From the above discussion, it is seen that the long-term performance of a geothermal reservoir depends on reservoir rock porosity, recharge, and... 

Hungary, Boldizsar (1970) estimated the lateral extent of the geopressurized reservoir to be 4000 km2, containing water at 60-200 °C. The geothermal reservoir water in Hungary is not so saline but relatively rich in C02. It is extensively exploited. 

Geothermal reservoir waters are close to calcite saturation. Degassing of such water, which occurs in response to boiling, leads to a sharp rise in the pH of the water. This in turn causes the activity of the carbonate ion (CO3-) to increase much, leading to oversaturation (Arnorsson 1989) ... 

Geothermal reservoir rocks are typically fractured and therefore exhibit variable and anisotropic permeability. For that reason it is neither possible to predict with confidence how an injection well may perform with respect to its injectivity nor with respect to which way the injected fluid will flow once it is in the reservoir. Because of this complication, the success of injection varies between fields and it is anticipated that a special injection scheme must be developed for each field depending on its characteristics, mainly the three-dimensional distribution of permeability and the waste fluid composition. Injection may require drilling of special wells. Alternatively, wells drilled for the purpose of production may not have adequate yield but can be used successfully as injection wells. When this is the case, no special wells need to be drilled for injection purposes, which reduces road building and therefore scenery spoliation. 

Arnorsson, S., Bjornsson, S., Muna, Z. W. Ojiambo, S. B. 1990. The use of gas chemistry to evaluate boiling processes and initial steam fractions in geothermal reservoirs with an example from the Olkaria field, Kenya. Geothermics, 19, 497-514. 

Clotworthy, A. 2000. Response of Wairakei geothermal reservoir to 40 years of production. In Proceedings World Geothermal Congress 2000, Kyushu-Tohoku, Japan, 28 May-10 June 2000, 2057-2062. 

Giggenbach, W. F. 1991. Chemical techniques in geothermal exploration. In D Amore F. (ed) Application of Geochemistry in Geothermal Reservoir Development. UNITAR/UNDP Centre on Small Energy Resources, Rome, 119-144. 

Richards, H. G., Savage, D. Andrews, J. N. 1992. Granite-water reactions in an experimental Hot Dry Rock geothermal reservoir Rosemanowes test site, CORNWALL, U. K. Applied Geochemistry, 7, 193-222. 

Rojas, J., Menjos, A., Martin, J. C., Criaud, A. Fouillac, C. 1987. Development and exploitation of low enthalpy geothermal systems example of the Dogger in the Paris Basin, France. In Proceedings of the 12th Workshop on Geothermal Reservoir Engineering, Stanford University, 203 -212. 

---