| Summary: | In this thesis a correlation between wellhead pressure, well bottom pressure, wellhead mass flow and wellhead enthalpy is found. From that correlation wellhead pressure is estimated for six wells in Svartsengi. An equation to describe output curves from a two phase flow geothermal wells from Kjaran and Elíasson (1983) is improved by including wellhead enthalpy of the geothermal fluid in the equation. Svartsengi is a high enthalpy geothermal system where low permeability caprock isolates the reservoir from colder groundwater aquifers above. Local fracturing allows for some geothermal fluids to escape and form localized steam zones. The enthalpy of the Svartsengi system has been increasing since production began and the steam zone has been expanding. Thorough geological and geophysical studies have been made in the Svartsengi area and a conceptual model has been developed. Two types of wells have been drilled in Svartsengi: water wells and steam wells. The former have two phase flow of water and steam but the latter have one phase flow of steam. For the steam wells, only pressure in the steam cap was simulated. For the water wells, output curves and wellhead pressure were simulated. The wellbore simulator WellSim was used for the well simulations. Based on simulations of output curves and wellhead pressure from three of the water wells, constants in an equation proposed by Kjaran and Elíasson were found as a function of enthalpy and more advanced equations were introduced. A set of equations incorporating the wellhead enthalpy is introduced and tested on the three simulated wells and three additional wells in Svartsengi. Í ritgerðinni er fjallað um borholur í jarðhitasvæðum og samband fundið milli holutopps þrýstings, holubotn þrýstings, massaflæðis í holutoppi og vermi jarðhitavökvans í holutoppi. Út frá þessu sambandi er holutoppsþrýstingur fyrir sex borholur í Svartsengi metinn. Jafna sem lýsir aflferlum úr tvífasa jarðhitaborholum sett fram af Kjaran og Elíasson (1983), er endurbætt með því að taka tillit ...
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