Numerical Simulation and Economic Evaluation of Wellbore Self-Circulation for Heat Extraction Using Cluster Horizontal Wells

Zhen Zhao, Guangxiong Qin, Huijuan Chen, Linchao Yang, Songhe Geng, Ronghua Wen and Liang Zhang
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Zhen Zhao: Faculty of Engineering, China University of Geosciences (Wuhan), Wuhan 430074, China
Guangxiong Qin: Qinghai Bureau of Environmental Geological Exploration, Xining 810001, China
Huijuan Chen: Qinghai Bureau of Environmental Geological Exploration, Xining 810001, China
Linchao Yang: School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China
Songhe Geng: School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China
Ronghua Wen: School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China
Liang Zhang: School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China

Energies, 2022, vol. 15, issue 9, 1-26

Abstract: The heat extraction capacity of the self-circulation wellbore is usually small because of the limited heat exchange area. In the paper, the cluster horizontal well group technology was proposed to enhance the heat extraction capacity and decrease the unit cost. Based on the mathematical model of heat transfer, a numerical simulation model of wellbore self-circulation for heat extraction using cluster horizontal wells was established to study the influence of main factors on heat extraction capacity. The economic analysis of heat extraction and power generation was carried out according to the model of the levelized cost of energy. The results show that the enhancement of heat extraction capacity is limited after the injection rate exceeds 432 m 3 /d (1.59 MW/well). The inflection point of the injection rate can be determined as the design basis for injection-production parameters. When the thermal conductivity of formation increases from 2 to 3.5 W/(m·K), the heat extraction rate will increase 1.45 times, indicating that the sandstone reservoirs with good thermal conductivity can be preferred as the heat extraction site. It is recommended that the well spacing of cluster wells is larger than 50 m to avoid the phenomenon of thermal short circuit between wells, and the thermal conductivity of the tubing should be less than 0.035 W/(m·K) to reduce the heat loss of heat-carrying fluid in the tubing. Compared with a single well, a cluster horizontal well group can reduce the unit cost of heat extraction and power generation by 24.3% and 25.5%, respectively. The economy can also be improved by optimizing heat-carrying fluids and retrofitting existing wells.

Keywords: cluster wells; wellbore self-circulation; heat extraction capacity; economic evaluation (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
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