基于裂隙粗糙性表征方法的地热岩体热流耦合数值模拟与分析

doi:10.11949/0438-1157.20221552

摘要/Abstract

摘要：

随着能源结构转型，干热岩等地热岩体得到了快速发展。地热岩体内部结构组成复杂，渗流与传热过程多变，如何针对岩体裂隙分布特征，建立更加精准的描述表征模型并进行多物理场耦合分析，有待深入探讨。基于裂隙粗糙性表征（joint roughness coefficient，JRC）描述方法，将表征单元体（representative elementary volume，REV）引入到JRC尺寸选取中，并将其应用于地热岩体物理模型中，采用数值模拟方法，对地热岩体温度场与渗流场进行了耦合分析。研究发现，裂隙附近温度场分布与裂隙的形态基本一致，表现出一种基岩温度场随着裂隙形态变化的波动性规律；流体注入速度和温度对系统运行达到稳态的时间影响呈负相关性；较低的注入速度和较高的注入温度都可以有效延长系统生产寿命，此外，通过对出口法向热通量的分析得出最佳注入流速。

关键词: 地热, JRC, 表征单元体, 传热, 传递过程, 数值模拟

Abstract:

With the transformation of energy structure, geothermal energy like dry hot rock has been rapidly developed. As the complex composite of the internal structure of the geothermal rock, as well as the changeable transfusion and heat transfer process, further discussion is needed as to how to establish a more accurate representation model and conduct multi-physical fields coupling analysis aiming at the distribution characteristics of rock fracture. Based on the description method of joint roughness coefficient (JRC), the representative elementary volume (REV) was introduced into the JRC size selection and it was applied into the geothermal rock physical model. The coupling analysis was conducted on the temperature field of geothermal rock and transfusion field by adopting numerical simulation method. It was found that the distribution of temperature field near the fracture was basically consistent with the fracture's morphology, showing a fluctuation law of the temperature field of bedrock with the change of the fracture morphology. There was a negative correlation between fluid injection speed and temperature on the time when the system reached steady state; both lower injection speed and higher injection temperature could effectively prolong the production life of the system; in addition, through the analysis of the outlet normal heat flux, it was concluded that the optimal injection velocity in this paper.

Key words: geothermal, JRC, representative elementary volume, heat transferr, transport processes, numerical simulation

中图分类号:

TK 529

王志国, 薛孟, 董芋双, 张田震, 秦晓凯, 韩强. 基于裂隙粗糙性表征方法的地热岩体热流耦合数值模拟与分析[J]. 化工学报, 2023, 74(S1): 223-234.

Zhiguo WANG, Meng XUE, Yushuang DONG, Tianzhen ZHANG, Xiaokai QIN, Qiang HAN. Numerical simulation and analysis of geothermal rock mass heat flow coupling based on fracture roughness characterization method[J]. CIESC Journal, 2023, 74(S1): 223-234.

图/表 17

图1 基于JRC的裂隙粗糙性表征示意图

Fig.1 Schematic diagram of crack roughness characterization based on JRC

图2 基于REV尺度的JRC值随特征尺寸变化表征图

Fig.2 Representation diagram of JRC value varying with feature size based on REV scale

图3 数字化基于RVE选取的JRC(8~10、10~12) 典型粗糙度曲线

Fig.3 The typical roughness curves of JRC (8—10, 10—12) selected based on RVE digitized

图4 REV尺度下基于JRC表征法的干热岩物理模型及二维概念模型

Fig.4 Physical model and two-dimensional conceptual model of hot and dry rock based on JRC characterization at REV scale

表1 裂隙岩体物性参数

Table 1 Physical parameters of fractured rock mass

介质

密度ρ/(kg/m³)

热导率λ/

(W/(m·K))

比热容C/

(J/(kg·K))

动力黏度

μ/(Pa·s)

图5 有限元模型网格

Fig.5 Finite element model grid

图6 模拟结果验证

Fig.6 Verification of simulation results

图7 模型温度分布场云图（vin=0.04 m/s）

Fig.7 Cloud image of model temperature distribution field (vin=0.04 m/s)

图8 温度等值线图（vin=0.04 m/s）

Fig.8 Model temperature contour map (vin=0.04 m/s)

图9 出口流体平均温度在不同流速下随时间变化图

Fig.9 The average temperature of outlet fluid changes with time at different flow rates

图10 不同粗糙度时出口平均温度随时间变化图

Fig.10 Time variation diagram of average temperature at outlet with different roughness

图11 系统寿命随流体注入速度变化情况图

Fig.11 System life as a function of fluid injection rate

图12 稳态时岩体平均温度和流体平均出口温度变化情况图

Fig.12 Figure of average rock mass temperature and fluid outlet temperature change in steady state

图13 稳态时不同注入流速下出口法向热通量变化情况

Fig.13 Change of outlet normal heat flux under different injection velocity in steady state

图14 不同注入温度时裂隙出口水平均温度随时间变化图

Fig.14 Time variation of average horizontal temperature at crack outlet at different injection temperatures

图15 系统寿命随流体注入温度变化情况图

Fig.15 System life as a function of fluid injection temperature

图16 稳态时岩体平均温度和流体平均出口温度对比

Fig.16 Comparison between average rock mass temperature and average fluid outlet temperature in steady state

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