Novel thermochemical fracturing: A breakthrough in sustainable and efficient enhanced geothermal systems (EGS)

Abstract

Enhanced geothermal systems (EGS) are crucial for accessing earth's vast geothermal potential, particularly in low-permeability formations. However, conventional EGS stimulation via hydraulic fracturing often entails high operational costs, substantial water consumption, potential environmental impacts, and risks of induced seismicity. This study presents a novel thermochemical fracturing approach to enhance EGS performance and sustainability while addressing these limitations. The in-situ exothermic reaction of sodium nitrite (NaNO₂) and ammonium chloride (NH₄Cl) was applied to a 12-inch carbonate rock sample. A specialized core flooding apparatus enabled real-time evaluation of temperature profiles, permeability, and heat transfer enhancements. The thermochemical stimulation increased permeability by 109% (from 19.01 to 39.70 mD) and enhanced heat transfer by 530%. These improvements stem from an extensive micro-fracture network generated by high-pressure nitrogen gas pulses, contrasting with larger planar fractures from hydraulic fracturing. Notably, this was achieved with only a 3.3% increase in porosity, indicating preserved rock integrity. The exothermic reaction prevented core cooling during ambient-temperature stimulation fluid injection, avoiding thermal shock. The thermochemical stimulation primarily generates nitrogen gas (N₂) and a brine solution as byproducts. The generated N₂ offers the additional benefit of providing well lifting energy, simplifying flowback operations. The novel application of thermochemical stimulation in EGS represents a promising, eco-friendly, and operationally efficient alternative to conventional EGS stimulation techniques.

Keywords

Energy sustainability / Enhanced geothermal systems / Thermochemical fluids / Fracturing treatment / Novel method

CRediT authorship contribution statement

Ahmed Al-Ghamdi: Methodology, Validation, Formal analysis, Writing-original draft, Investigation, Data curation. Amjed Hassan: Writing-review & editing, Supervision, Investigation, Data curation, Validation, Methodology, Conceptualization, Writing-original draft, Formal analysis. Mohamed Mahmoud: Visualization, Investigation, Writing-review & editing, Validation, Formal analysis, Conceptualization, Supervision, Data curation. Talal Al-Shafloot: Writing-review & editing, Data curation, Investigation, Supervision, Formal analysis, Conceptualization.

Declaration of competing interest

The Authors declare that they have not conflict of interest.

Acknowledgements

The College of Petroleum and Geoscience (CPG) at King Fahd University of Petroleum and Minerals (KFUPM) is acknowledged for the support and permission to publish this work.

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