Fracture Performance Impairment and Mitigation Strategies

Abstract

Hydraulic fracturing is the key stimulation technology for sedimentary geothermal reservoirs. The technology is widely known from hydrocarbon exploitation. Nevertheless, for geothermal purposes it has to be adapted and further developed to reach high fluid production rates. Putting primary low-productive but widely spread aquifer structures in use for geothermal power generation is the main goal of an extensive research campaign in Germany.
Fracture characteristics and performance can be modelled by matching it to observed field data. The effectiveness of a fracture, concerning its stimulation potential, is highly depending on its long-term conductivity. The latter can be highly deteriorated by mechanical, hydraulic and chemical processes starting with fracture creation and being enhanced with the onset of production. Productivity impairment can be significantly decreased by a proper, site specific frac design. Therefore, the relevant damaging effects have to be qualified and quantified.
Stimulation experiments on a geothermal research well serve as case studies in this context. Furthermore, different hydraulic fracturing concepts are evaluated and compared in terms of their applicability and effectiveness in the investigated geologic environment. Insights gained can be transferred to geologically similar sites in order to increase the success of hydraulic fracturing operations and therefore the feasibility of the general reservoir development concept.