Zonal Isolation in Geothermal Wells

Abstract

Well integrity has had an utmost importance for oil and gas wells and many studies have been conducted to improve zonal isolation. However, few papers comprehensively investigated the importance of well integrity and zonal isolation in geothermal wells. Geothermal energy is generated in over 20 countries and the United States is the world's largest producer. This clean source of energy has been benefiting the nation from the operational geothermal projects in California, Nevada, Alaska and Hawaii as well as around the world. Geothermal energy has been considered as one of the main clean resources of energy which its fields produce only about one-sixth of the carbon dioxide that a relatively clean natural-gas-fueled power plant produces. The objective of this paper is to investigate the practical solutions for effective zonal isolation in geothermal wells. Viable solutions for extreme high temperatures, lost circulation, CO2 attack, in addition to cement and casing integrity are defined and applied. The case studies reviewed demonstrates the crucial role of these critical elements for safe and environmentally friendly geothermal wells. This analysis helps providing proper wellbore integrity for safe geothermal operation which doubtlessly is the most critical factor towards providing good zonal isolation.