temperature and pressure in the svartsengi ... - Orkustofnun

1 9Fresh water is pumped from shallow wells at a distance of 4to 5 km from the plant. There Is a fresh water lens ofonly 45 m thickness in porous surface lavas. The lens IsfloatIng on top of the seawater below. The pumping is donewith great care in order to avoid pumping "salt ll waterwhich could happen if the drawdown of the fresh watersurface in the well Is too much .2.6 Proposed reservoir model by Kjaran et al. (1979)This conceptual model for the regIonal geothermal system isa hybrid convection model for the geotherma! area itselflinking together reservoir performance and well performanceto give an estimate of the reservoir capacity.Free convection exists to some extent in most geothermalreservoirs (Ellasson, 1973). increasing considerably thenormal heat flow to the surface. The heat flux has topenetrate the caprock and it can be shown that it is almostimpossible that heat transport be only by conduction.There has to be some heat trans port by discharge of hotwater and steam to keep the convection going. If there issuch an outflow from the reservoir it must be expected tobe balanced by an equal amount of inflow . This inflow isassumed to be the infiltration at lake Kleifarvatn,flowing along the main earthquake zone, as shown in Fig. 5.The recharge and discharge flow and the convection are thepremise for the hybrid convection model shown in Fig. 5.From this figure one can wr i tethree continuity equations at eachequations are: continuity of mass,down six e quat ions:point E and D. Theenthalpy and chlorideconcentration. There are six equations and twelve unknowns.So six unknowns have to be assumed. At Svartsengi theseparameters were either measured or estimated thus enablingthe authors to solve for the remaining unknowns. Thenatural heat loss can then be calculated as the differenceof the upward and downward heat flow. The calculated valuewas about 300 MW, which was three times the necessary power