Performance evaluation of enhanced geothermal systems with intermittent thermal extraction for sustainable energy production

Abstract

Efficient extraction of thermal energy from deep geothermal reservoirs using Enhanced Geothermal Systems (EGS) is fundamental for sustainable clean energy generation. This study presents the Intermittent Thermal Extraction (ITE) method, addressing thermal breakthrough challenges encountered during continuous thermal extraction (CTE) within EGS reservoirs. Employing a thermal-hydraulic coupled approach and discrete fracture network modeling, the ITE process for EGS reservoirs is assessed, omitting considerations of stress-induced deformation. The research evaluates the ITE and CTE methods within a typical high-temperature geothermal reservoir in the Himalayan geothermal belt. Analysis includes variations in reservoir temperatures and pressures, alongside an examination of rock matrix permeability and injection fluid temperature impacts on EGS thermal extraction performance. Results demonstrate the ITE method's efficacy in prolonging the EGS reservoir lifespan by preventing thermal breakthroughs and maintaining pressure equilibrium. Under studied conditions, ITE extends the EGS reservoir lifespan by a minimum of 17.7 years, amplifying clean power generation by 13.1% compared to CTE. Additionally, ITE implementation substantially reduces greenhouse gas emissions by an estimated 1.46–5.03 million tons. The rock matrix permeability and injection fluid temperature significantly affect the EGS thermal extraction performance when the fracture aperture is constant. These findings highlight the ITE method's potential to optimize thermal extraction from EGS reservoirs, particularly in remote regions. This study contributes essential insights into advancing geothermal energy extraction techniques, emphasizing ITE as a promising approach for sustainable energy production.