Single-well in-situ heat extraction technology—a review and perspectives

doi:10.13745/j.esf.sf.2024.7.19

Abstract

Abstract:

Geothermal energy is a widely distributed, stable, sustainable, clean, and low-carbon renewable energy resource, and the only renewable energy that exists in the form of thermal energy. Efficient development and utilization of geothermal energy can not only meet the needs of building heating in northern China but also alleviate the country’s power shortages. This is of significant importance for achieving China’s dual carbon (carbon peak and carbon neutrality) goals. Used best for heating, geothermal energy poses a natural advantage over other renewable energies in building heating. Currently, however, geothermal energy utilization in China only accounts for ~1.5% of the country’s total energy consumption, far below the one-third share of energy consumption by buildings. For many years China has maintained a worldwide leader in geothermal direct use, but ~60% of which comes from shallow ground-source heat pumps. The traditional use of geothermal energy is relatively low, mainly because the conventional geothermal production and reinjection modes largely rely on the local hydrogeological conditions, and reinjection is difficult or uneconomical in some sandstone formations. As a result, government have tightened control on geothermal resources to prevent the rapid decline of water levels. In recent years, the “no-water-withdrawal-heat-only” single-well geothermal system has gained widespread attention. This technology eliminates reinjection issues and adapts well to the current energy development and utilization situation in China, offering excellent application prospects. This paper provides a brief overview of the research and application status of single-well heat extraction technology, focusing on the status of interactional and domestic researches on the no-water-withdrawal-heat-only technology. The basic principles and shortcomings of different single-well technologies are analyzed, emphasizing the importance of implementing site-specific in-situ technologies. The paper proposes that deep single-well heat extraction technology is an environmentally friendly, sustainable, and stable heating model that can effectively address the issue of building heating in winter in northern China. This technology has gained a certain level of market competitiveness with the advancement of drilling technology. It is recommended that relevent management policies should be formulated, which are crucial for promoting geothermal energy utilization in China and achieving the “dual carbon” goals.

Key words: geothermal energy, single-well, no water withdrawn but heat only, sustainable utilization

CLC Number:

P314

DAI Chuanshan, LIU Dongxi, LI Jiashu, LEI Haiyan, CHEN Shuhuan, CHEN Qianhan, WANG Qilong. Single-well in-situ heat extraction technology—a review and perspectives[J]. Earth Science Frontiers, 2024, 31(6): 204-214.

Figures/Tables 9

Fig.1 Typical techniques of heat extraction from a single geothermal well. Modified after [10⇓⇓⇓⇓⇓-16].

Fig.2 Typical designs of shallow downhole heat exchangers. Modified after [22⇓⇓-25].

Fig.3 Statistics of published research papers on deep borehole heat exchangers

Fig.4 Number of patent applications related to DBHE in China

Table 1 Summary of field tests on heat extraction from a single geothermal well

文献	井深/m	井底温度/℃	热输出/kW	延米功率/(W·m^-1)	试验地点
Morita^{a [27]}	876.5	110.3	76	86	美国,Hawaii
Kohl^a[28]	1 213	45	80	66	瑞士,Weissbad
Kohl^{a [29]}	2 302	78	100	43	瑞士,Weggis
Dijkshoorn^{a [30]}	2 500	85	117	47	德国,Aachen
Wang^{a [31]}	2 000		286	143	中国,西安
Deng^{a [32]}	2 000 2 000 2 000 2 500 2 000		258 158 288 273 122	129 79 144 109 61	中国,西安
卜宪标 $a$ ^[33]	2 605	85	448.49	172	中国,青岛
Zhan $g a$ ^[34]	1 800	57	134	75	中国,雄安
Huan $g a$ ^[35]	2 044	107.3		238	中国,松原
L $i a$ ^[36]	2 539	89	480	189	中国,西安
Ma^{a [37]}	2 000		266	133	中国,天津
Huan $g b$ ^[16]	3 000	128	190	63	中国,唐山
Yi $n c$ ^[38]	1 751	71	930	531	中国,天津
Michael^{c [39]}	2 000	69	363	181.5	英国,Cornwall
李嘉舒 $c$ ^[26]	1 400	68	450	320	中国,唐山

Table 1 Summary of field tests on heat extraction from a single geothermal well

文献	井深/m	井底温度/℃	热输出/kW	延米功率/(W·m^-1)	试验地点
Morita^{a [27]}	876.5	110.3	76	86	美国,Hawaii
Kohl^a[28]	1 213	45	80	66	瑞士,Weissbad
Kohl^{a [29]}	2 302	78	100	43	瑞士,Weggis
Dijkshoorn^{a [30]}	2 500	85	117	47	德国,Aachen
Wang^{a [31]}	2 000		286	143	中国,西安
Deng^{a [32]}	2 000 2 000 2 000 2 500 2 000		258 158 288 273 122	129 79 144 109 61	中国,西安
卜宪标 $a$ ^[33]	2 605	85	448.49	172	中国,青岛
Zhan $g a$ ^[34]	1 800	57	134	75	中国,雄安
Huan $g a$ ^[35]	2 044	107.3		238	中国,松原
L $i a$ ^[36]	2 539	89	480	189	中国,西安
Ma^{a [37]}	2 000		266	133	中国,天津
Huan $g b$ ^[16]	3 000	128	190	63	中国,唐山
Yi $n c$ ^[38]	1 751	71	930	531	中国,天津
Michael^{c [39]}	2 000	69	363	181.5	英国,Cornwall
李嘉舒 $c$ ^[26]	1 400	68	450	320	中国,唐山

Fig.5 Plot of heat extraction rate per wellbore length vs. well depth

Fig.6 Numerical simulation results on natural convection (in cavity partially filled with porous media), temperature contour and streamline using different physical models. Adapted from [47-48].

Fig.7 Comparison of experimental and simulation results for heat extraction with a DOLGW design (Tangshan, Hebei, China)

Fig.8 The heat extraction rate and outlet water temperature after 10 years of system operation

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