1 Stimulation of geothermal wells in basaltic rock in Iceland

• Main Authors: Gudni Axelsson, Sverrir Thórhallsson, Grímur Björnsson
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2006
• Subjects: geothermal; volcanic; stimulation; Iceland
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.485.4145; http://engine.brgm.fr/web-offlines/conference-Mid-Term_Conference_-_Potsdam,_Germany/other_contributions/44-paper-0-GAxIcelStimEngineJune06.pdf

Stimulation operations are commonly part of the completion programs of geothermal wells drilled in the basaltic environment of Iceland. The purpose is to enhance the output of the wells either by improving near-well permea-bility that has been reduced by the drilling ope-ration itself or to open up hydrological conn-ections to permeable zones not intersected by the well in question. The methods used involve applying high-pressure water injection, some-times through open-hole packers, or inter-mittent cold water injection with the purpose of thermal shocking. Stimulation operations are most commonly applied for a few hours to a few days while in a few instances stimulation operations have been conducted for some months. The stimulation operations often result in well productivity being improved by a factor of 2-3. Emphasis is placed on careful reservoir monitoring during stimulation op-erations. Seismic monitoring has only been applied in a few cases and examples are avail-able where long-term water injection has caus-ed a marked change in seismic activity as well situations where long-term high-pressure in-jection has caused no micro-seismic activity at all.