A Technology Roadmap for Strategic Development of Enhanced Geothermal Systems

Abstract

Roughly 90% of the geothermal power resource in the United States is thought to reside in Enhanced Geothermal Systems (EGS). While realization of EGS development on the 100+ GWe scale would make geothermal a significant component of the renewable energy portfolio, hurdles to commercial development still remain in accessing and characterizing, creating, monitoring, operating, and sustaining engineered reservoirs. In August 2011 the Geothermal Technologies Office (GTO), U.S. Department of Energy (DOE), convened a workshop in San Francisco, CA, to outline opportunities for advancing EGS technologies on five-to 20-year timescales. Community input charted technology needs categorized within the functional stages of Characterizing, Creating, and Operating EGS reservoirs. In this paper we present technical paths identifying, creating, and managing fractures and flow paths; monitoring flow paths and fracture evolution; zonal isolation; drilling; models; and tools that encompass the underlying technology needs identified at the workshop as critical to optimizing and ultimately commercializing EGS. We develop the chronological evolution of these paths, tying the past and current status of each to the active GTO EGS research and development (R&D) portfolio, anticipating milestones that strategic initiatives could help to realize on a five-year timescale, and projecting to target capabilities for 2030. The resulting structure forms the basis for an EGS Technology Roadmap to help guide priorities for future GTO EGS R&D investments. State of EGS Since the early 1970s, several large-scale EGS field projects reached varying degrees of success, though the majority of EGS developers and researchers would conclude that EGS has yet to be validated as an optimized technology on a commercial scale. Fenton Hill, Rosemanowes, Le Mayet, Hijiori, Soultz, and Cooper Basin (Wyborn, 2011) targeted granitic reservoir host rocks at depths in excess of 2 km to achieve temperatures sufficient for electric power production. With the exception of the Landau project in Germany, past projects have not successfully sustained commercial production rates (50-100 kg/sec). Note that the characteristics of Landau suggest that it is a stimulated hydrothermal reservoir and not a "green-field" EGS development (e.g., Baria and Petty, 2008). Each of these historic EGS projects, however, has played an integral role in informing the future direction of EGS research and development, having added significantly to our understanding of micro to macro-scale issues associated with EGS.

The Future of Low-Carbon Electricity

“…EGS has the potential to access geothermal resources at greater depth and could add >100 GW of capacity in the U.S. (29). A key enabling technology is hydraulic fracturing to increase permeability (30), similar to that used to produce unconventional natural gas. Strongly supported by the U.S. DOE, the technology is still at a research and development (R&D) stage, with goals to demonstrate a 5 MW system by 2020, and a cost-reduction pathway from ~240 to ~60 USD/MWh by 2030 (30).…”

Problems and outlooks for petrothermal power engineering (review)

“…The US authorities have a roadmap for GCS development (Ziagos et al, 2013), The data of JAS (Joint Association on Survey on Drilling): oil-and-gas moderate (1) and deep (2) wells; wells from site "The Geysers", USA (3); calculations for geothermal wells (4); wells "The Imperial Valley", USA (5); other geothermal wells (6); petrothermal wells for enhanced geothermal systems (HDR/EGS): actual (7), model calculation (8); wells "Soults" (France) and "Cooper Basin" (Australia) (9); calculation with a simple model for drilling cost: conventional wells (10) and specialty wells (11).…”

Production capacity and mining plan optimization of fault/fracture‐controlled EGS model in Gonghe Basin

“…The Fenton Hill site was the first tested HDR project in 1974, and the great potential and feasibility of the EGS concept have been heralded to exploit thermal energy after 40 years of engineering testing . Then, the Desert peak and Geysers projects (USA), Rosemanows project (UK), Soultz project (France), Ogachi and Hijiori projects (Japan), Gross Schoenebeck project (Germany), and Cooper Basin project (Australia) were built . It is noteworthy that China occupies 7.9% of the world's geothermal energy reserves, at 3.06 × 10 18 kWh/y, and the HDR resource could reach 2.09 × 10 7 EJ within subsurface 3‐10 km subsurface .…”