增强型地热系统储层裂隙非线性渗流与传热机理研究

Geothermal energy in hot dry rock is environmental friendly and renewable, which has large potential in the recent society. However, many scientific and technological issues need to be solved during the process. This project focuses on the non-linear flow and heat transfer characteristics in artificial fracture network associated with enhanced geothermal system in hot dry rock. Experimental studies, theoretical analysis and numerical simulations on non-linear flow characteristic and heat transfer mechanism of artificial fracture network are conducted. First, we will investigate the complex flow process and heat transfer characteristics in fractures and examine the combined influences of joint geometric morphology, temperature, in-situ stress and injection pressure on non-linear flow characteristic and heat transfer efficiency. A non-linear flow model will then be proposed. Second, the effects of joint geometric morphology, temperature and water pressure on the heat transfer characteristics in fractures are studied and a model for heat transfer will be established. At last, the coupling mechanism of non-linear flow and heat transfer of fractured rock mass in depth under the effects of stress field, seepage field and thermal field are investigated. The mathematical model for THM coupling of artificial fracture network is established and the corresponding computational program will be compiled. The numerical analysis of non-linear flow and heat transfer processes of artificial fracture network during exploitation of geothermal energy. The study can provide an important theoretical contribution to the issue of optimal design of geothermal energy exploitation.

干热岩地热资源为清洁可再生能源，但其开采难度大技术要求高。本项目以干热岩增强型地热系统(EGS)的人工裂隙渗流与传热规律为研究内容，开展高温储层裂隙非线性渗流规律与传热机理实验研究、理论建模和数值模拟分析。研究储层岩石裂隙复杂渗流和对流传热规律，揭示裂隙几何形貌、储层温度、深部地应力、注采渗流水压等因素对裂隙非线性渗流规律和对流换热效率的综合控制作用，建立储层裂隙非线性渗流模型；掌握储层裂隙几何特征、温度、水压等对裂隙对流传热规律的影响，建立考虑温度和形貌因素的裂隙对流传热模型。研究地热开采过程中深部储层岩体和裂隙在应力场、渗流场和温度场共同作用下的渗流与传热耦合机理，建立地热储层裂隙流固热耦合数学模型，开发耦合计算程序并进行地热开采过程裂隙复杂渗流和传热规律的模拟分析，为地热能开采方案的优化设计提供理论与技术支持。

裂隙渗流与传热规律是干热岩增强型地热系统(EGS)应用过程中亟待解决的基础性科学问题，但针对高温储层裂隙的渗流规律和对流传热机理仍未深入掌握。本项目以干热岩增强型地热系统(EGS)的人工裂隙渗流与传热规律为研究内容，开展高温储层裂隙非线性渗流规律与传热机理实验研究、理论建模和数值模拟分析。通过分析裂隙渗流传热特性的形貌影响，并研制了岩石裂隙剪切渗流传热实验系统，通过推导裂隙渗流传热过程中换热系数模型，研究增强型地热系统热开采效率与生产寿命评价的数值模拟；通过数值评估研究了裂隙储层的多项特征因素对增强型地热系统热采性能的影响，探明岩石裂隙热传输机理与效率。本研究为探明干热岩增强型地热系统中人工裂隙渗流规律与传热机理提供理论方法。