Review of Well Stimulation Operations in Iceland

Abstract

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 permeability that has been reduced by the drilling operation itself or to open up hydrological connections to permeable zones not intersected by the well. The methods most commonly used involve applying high-pressure water injection, sometimes through open-hole packers, or intermittent cold water injection with the purpose of thermal shocking. Stimulation operations commonly last a few days while in some 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 operations. Seismic monitoring has provided valuable information in a few cases. Further research and “state of the art” technology are needed to better understand stimulation processes and to improve the outcome of geothermal stimulation operations.