| Abstract |
In both conventional geothermal projects and in EGS, the flow rate from each production well is the critical component of project economics and has a direct effect on the Levelized Cost of Electricity (LCOE). In conventional geothermal fields, the cost of the wellfield system makes up 25% - 50% of the total cost of the project. In EGS the wellfield makes up 60%-80% of the cost of the project. While intersecting adequate temperatures during drilling is a significant risk, low temperatures can be compensated by high flow rates. In EGS projects, the temperature is primarily a function of the drilling depth, so the ability to stimulate and achieve a high production rate without risking rapid temperature drop is critical not only to project economics, but also to expansion of the development of geothermal energy into areas where hydrothermal resources are not found. The oil and gas industry has developed stimulation techniques over the years that have allowed the enhancement of very low permeability rock for oil and gas production. Multi-stage stimulation and horizontal well completions can access larger volumes of tight rock to recover poorly connected pore volume. These technology changes in oil and gas stimulation have allowed the development of a resource that was previously thought to be uneconomic. In unconventional oil and gas resources, the permeability of shale is very low, just as heat transfer in rock is very small. The larger the surface area of the contact with the formation, the more production is possible. By focusing our efforts in geothermal energy technology on improving production and injection rates through stimulation, improving power plant efficiency to get more power output from the same flow and temperature and by managing the reservoir to reduce pressure and temperature decline, we can mitigate exploration risk and expand the base of geothermal power production. The Newberry Volcano EGS Demonstration is not only a demonstration of an enhanced geothermal system, but a further demonstration of the benefit of multi-stage fracturing relying largely on hydroshearing. AltaRock has performed three stimulations using thermally degrading zonal isolation materials (TZIM) to block permeable zones and create multiple stimulated fracture systems in conventional geothermal reservoirs. These stimulations targeted deep, high temperature areas of the reservoir while isolating and preventing stimulation of shallow, low temperature zones. Previous results show not only up to 60% increase in flow rate, whether injection or production, but the production and or injection improvement is confined to higher temperature zones. Interim results from the Newberry EGS stimulation of multiple zones are discussed. |