Stimulation Techniques Used in Enhanced Geothermal Systems: Perspectives from Geomechanics and Rock Physics

Abstract

Understanding the processes that enhance fluid flow in crustal rocks is a key step towards extracting sustainable thermal energy from the Earth. To achieve this, geoscientists need to identify the fundamental parameters that govern how rocks respond to stimulation techniques, as well as the factors that control the evolution of permeability networks.

These parameters must be assessed over a variety of spatial scales: from microscopic rock properties (such as petrologic, mechanical, and diagenetic characteristics) to macroscopic crustal behavior (such as tectonic and hydro-dynamic properties). Furthermore, these factors must be suitably monitored and/or characterized over a range of temporal scales before the evolutionary behavior of geothermal fields can be properly assessed. We are reviewing the procedures currently employed for reservoir stimulation of geothermal fields.

The techniques are analyzed in the context of the petrophysical characteristics of reservoir lithologies, studies of wellbore data, and research on the regional crustal properties. The analyses are then used to correlate the relative success of stimulation techniques with the observable and/or measurable spatio-temporal characteristics of the geothermal reservoir. The results of these correlations can then help to guide procedures employed when targeting new prospective geothermal resources.