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深层地热能丛式多分支U型井采热技术及传热算法

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深层地热能是一种分布广、资源量大具有发展前景的可再生新能源,当前的主要开采方法有增强型地热系统(EGS)、环绕式井筒换热系统(AGS)、断层带流体循环开采和同轴套管开采法,但存在采热功率不稳定、地震风险高和采热效率低等难题.针对当前深层地热开采技术面临的瓶颈问题,本文以开采过程只有能量交换而没有物质交换为原则,以深层干热岩地热规模化可持续稳定开发为目标,提出了深层地热能丛式多分支U型井采热方法(UMW-DGS)及关键技术,在此基础上建立了井筒轴对称热传导模型,以青海共和盆地恰卜恰深部干热岩储层为背景,提出了高温高压岩石热导率测试新方法,计算了在定井径条件下井周温度场和采热功率的时空演化规律,分析了温度差、热导率和井径等3个敏感因素对采热功率的影响.此外,针对UMW-DGS定解问题,研发了基于有限体积法(FVM)的三维热流固耦合数值算法,研究了 UMW-DGS单水平井段换热效率和在不同泵注量条件下温度场时空演化.通过分析不同流量的有效换热量、换热时长和功率发现:泵注流量的增加会导致有效换热能量和有效换热时长的降低,并且使有效换热功率先增加后减少.研究结果表明,深层地热能开发需要在平衡换热温度和功率的条件下设计注入排量,从而得到最优的换热效果.
U-SHAPED MULTIBRANCH WELLS(UMW)AND HEAT TRANSFER AL-GORITHM FOR DEEP GEOTHERMAL SYSTEM
Deep geothermal energy is a renewable energy source with broad distribution,vast resource potential,and promising development prospects.Current main extraction methods include enhanced geothermal systems(EGS),annular heat exchange well systems(AGS),fault zone fluid circulation extraction,and coaxial casing ex-traction methods.However,challenges such as unstable heat extraction power,high seismic risks,and low heat ex-traction efficiency persist.Addressing the bottlenecks in current deep geothermal extraction technology,this paper adheres to the principle of energy exchange without material exchange during the extraction process and aims for large-scale,sustainable,and stable development of deep dry hot rock geothermal resources.We propose the clus-tered multi-branch U-shaped well heat extraction method(UMW-DGS)and its key technologies.On this basis,an axisymmetric thermal conduction model for the wellbore is established.Using the deep dry hot rock reservoir in the Qabqa area of the Gonghe Basin in Qinghai as a case study,a new method for testing the thermal conductivity of high-temperature and high-pressure rocks is proposed.We calculated the spatiotemporal evolution of the temperature field and heat extraction power around the well under constant wellbore diameter conditions and analyzed the effects of three sensitive factors—temperature difference,thermal conductivity,and wellbore diameter—on heat extraction power.Additionally,to address the boundary value problem of the UMW-DGS,a three-dimensional thermo-hydro-mechanical coupling numerical algorithm based on the finite volume method(FVM)was developed.This algorithm was used to study the heat exchange efficiency of a single horizontal well section of the UMW-DGS and the spatio-temporal evolution of the temperature field under different injection flow conditions.By analyzing the effective heat exchange amount,duration,and power at different flow rates,we found that increasing the injection flow rate de-creases the effective heat exchange energy and duration while causing the effective heat exchange power to first in-crease and then decrease.The research results indicate that deep geothermal energy development requires designing injection flow rates to balance heat exchange temperature and power for optimal heat exchange efficiency.

Deep geothermal energyClustered multi-branch U-shaped wellsThermal conductivity of high-tem-perature and high-pressure rocksReservoir-working fluid thermo-hydro-mechanical coupled heat conduction algo-rithm

李守定、张苏鹏、徐涛、张召彬、郑博、马世伟、孔彦龙、张文秀、赫建明、庞忠和、李晓

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中国科学院地质与地球物理研究所,中国科学院页岩气与地质工程重点实验室,北京 100029,中国

中国科学院大学,地球与行星科学学院,北京 100049,中国

中国科学院地球科学研究院,北京 100029,中国

中国科学院地质与地球物理研究所,中国科学院深地资源装备技术工程实验室,北京 100029,中国

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深层地热 丛式多分支U型井 高温高压岩石热导率 储层-工质流固耦合热传导算法

国家自然科学基金项目&&中国科学院地质与地球物理研究所部署项目

521926232022DJ5503IGGCAS-202203

2024

10.13544/j.cnki.jeg.2024-0399

工程地质学报
中国科学院地质与地球物理研究所

工程地质学报

CSTPCD北大核心
影响因子：1.215
ISSN：1004-9665
年,卷(期)：2024.32(4)