Heat Extraction in Geothermal Systems with Variable Thermo-Poroelastic Fracture Apertures

IF 2.2 4区工程技术 Q3 ENGINEERING, GEOLOGICAL

Environmental geotechnics Pub Date : 2023-11-03 DOI:10.3390/geotechnics3040065

Mrityunjay Singh, Saeed Mahmoodpour, Kristian Bär, Ingo Sass

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Abstract

The fracture network largely determines the efficiency of heat extraction from fractured geothermal reservoirs. Fracture openings are influenced by thermo-poroelastic stresses during cold fluid flow, with the interplay between fracture length and fracture opening regulating heat transfer. The lack of field data concerning fluctuating fracture openings underscores the necessity for computational models. This work emphasizes the impact of such gaps in the literature. Factors such as temperature, pressure, stress, thermal breakthrough time, and cumulative energy are evaluated to analyze the system’s behavior. A sensitivity analysis is employed to ascertain the significance of stress on fracture opening, compared with thermo-hydraulic behavior. The results show that stress field alterations, due to intersections with minor fractures, can cause up to a 15% variation in the largest fracture’s opening. The impact of thermoelastic stress outweighs the impact of poroelastic stress approximately threefold. Such stress-induced variations in fracture openings can lead to an up to 30% increase in cumulative heat extraction, while the drop in production temperature is limited to around 50%.

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具有可变热孔弹性裂缝孔径的地热系统的热提取

裂缝网络在很大程度上决定了裂缝性地热储层的采热效率。在冷流体流动过程中，裂缝开度受热孔弹性应力的影响，裂缝长度和裂缝开度之间的相互作用调节着传热。由于缺乏有关波动裂缝开度的现场数据，因此需要建立计算模型。这项工作强调了这些差距在文献中的影响。对温度、压力、应力、热突破时间和累积能量等因素进行评估，以分析系统的行为。采用敏感性分析来确定应力对裂缝张开的重要性，并与热水力行为进行比较。结果表明，由于与小裂缝相交，应力场变化可导致最大裂缝开度变化15%。热弹性应力的影响超过孔弹性应力的影响约三倍。这种应力引起的裂缝开度变化可能导致累计热抽提量增加30%，而生产温度下降限制在50%左右。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Environmental geotechnics Environmental Science-Water Science and Technology

CiteScore

6.20

自引率

18.20%

发文量

期刊介绍： In 21st century living, engineers and researchers need to deal with growing problems related to climate change, oil and water storage, handling, storage and disposal of toxic and hazardous wastes, remediation of contaminated sites, sustainable development and energy derived from the ground. Environmental Geotechnics aims to disseminate knowledge and provides a fresh perspective regarding the basic concepts, theory, techniques and field applicability of innovative testing and analysis methodologies and engineering practices in geoenvironmental engineering. The journal''s Editor in Chief is a Member of the Committee on Publication Ethics. All relevant papers are carefully considered, vetted by a distinguished team of international experts and rapidly published. Full research papers, short communications and comprehensive review articles are published under the following broad subject categories: geochemistry and geohydrology, soil and rock physics, biological processes in soil, soil-atmosphere interaction, electrical, electromagnetic and thermal characteristics of porous media, waste management, utilization of wastes, multiphase science, landslide wasting, soil and water conservation, sensor development and applications, the impact of climatic changes on geoenvironmental, geothermal/ground-source energy, carbon sequestration, oil and gas extraction techniques, uncertainty, reliability and risk, monitoring and forensic geotechnics.