The use of gas chemistry to evaluate boiling processes and initial steam fractions in geothermal reservoirs with an example from the olkaria field, Kenya

Stefán Arnórsson*, Sveinbjörn Björnsson, Zach Wambua Muna, Sebastian Bwire-Ojiambo

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

A method has been developed to evaluate boiling processes in the producing aquifer of "high-enthalpy" geothermal wells using data on the concentrations of CO2, H2S and H2 in steam discharged. The extent to which water and steam are separated in the producing aquifer is evaluated as well as the amount of enhanced evaporation due to heat flow from the rock to the boiling water. Further, the initial steam fraction in the reservoir fluid is calculated. Results are presented for the Olkaria geothermal field, Kenya, to demonstrate the use of our method. They show that the initial steam fraction in the reservoir is very small: up to 0.25% of the mass, or about 10% by volume. Segregation of water and steam in the producing aquifers is rather extensive for some of the wells. Thus, water which has boiled and yielded steam into wells amounts to more than two times the mass of the fluid discharged from the well. The larger part of the exploited steam ( 3 4) is generated by flow of heat from the rock to the boiling water.

Original languageEnglish
Pages (from-to)497-514
Number of pages18
JournalGeothermics
Volume19
Issue number6
DOIs
Publication statusPublished - 1990

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