Work

Numerical Simulation Study on the Natural Temperature Recovery Characteristics of Reservoirs After Shutdown in a Dual-Well Enhanced Geothermal System

Year: 2025

Type: article

Abstract: In the context of energy structure transition, Enhanced Geothermal Systems (EGSs) represent a core technology for developing hot dry rock (HDR) resources. However, the ultra-long-term natural recovery patterns of reservoir temperature after heat extraction cessation remain unclear, hindering sustainable lifecycle assessment of the system. This study establishes a dual-well EGS numerical model based on the finite element method to simulate the impact mechanisms of flow rate, injection temperature, initial reservoir temperature, and well spacing on natural reservoir temperature compensation during a 1000-year shut-in period following 40 years of heat extraction. Results indicate that reservoir temperature fails to recover to its initial state after shut-in, with final recovery rates ranging from 60.63% to 89.51% of the initial temperature. Each parameter exerts nonlinear control over recovery: lower flow rates yield higher final recovery temperatures (87.62% at 20 kg/s versus 60.63% at 100 kg/s); increased injection temperature from 10 °C to 70 °C reduces the absolute recovery magnitude from 10.65 °C to 7.05 °C but raises the final recovery rate from 78.16% to 86.07%; higher initial reservoir temperatures from 100 °C to 260 °C significantly enhance absolute recovery temperatures from 79.48 °C to 199.58 °C; reduced well spacing from 500 m to 100 m improves final recovery rates from 72.77% to 89.51%. After shut-in in dual-well EGS, the vertical fracture configuration recovered to 78.16% of the initial temperature, the horizontal fracture to 74.39%, and the no-fracture configuration only to 67.87%. Due to optimal heat flow and thermal compensation efficiency, vertical fractures exhibit the best recovery performance, while the no-fracture configuration shows the worst. This study reveals the dynamic mechanism of heat recovery dominated by heat conduction in surrounding rocks, establishes a long-term temperature recovery evaluation framework for EGS, and provides novel scientific evidence and perspectives for the sustainable development and research of geothermal systems.

Source: Processes

DOI: 10.3390/pr14010075

Authors: Jun Zhang, Weixing Yang, Minghe Yang, Xulong Cai

Institutions: Sinopec (China), Sinopec Northwest Oil Field Company (China), Yangtze University, Xi'an Jiaotong University

Language: English

Topic: Geothermal Energy Systems and Applications

Subfield: Renewable Energy, Sustainability and the Environment

Field: Energy

Domain: Physical Sciences

SDGs: Affordable and clean energy, Climate action

Open Access status: gold

Estimated APC paid: $2,896