双重介质热-水-力三维耦合模型及应用

3D Dual Medium Model of Thermal-Hydro-Mechanical Coupling and Its Application

在建立双重介质热-水-力耦合微分控制方程的基础上,提出了高温岩体地热开发系统热-水-力耦合的双重介质模型,对不同的介质分别建立以结点位移、水压力和温度为求解量的三维有限元格式,提出了该数学模型的求解策略与方法,开发了双重介质热-水-力耦合分析的的三维有限元计算程序DTHM.for,对地下-6km的高温岩体地热开发进行了详细的数值分析,结果表明:随地热提取,岩体裂缝法向应力逐渐降低、裂缝宽度成非线性增长;开始运行阶段,拟连续基岩介质内水压上升滞后,1a左右,整个系统水压保持稳定,以固定的压力梯度流动,在注入井和生产井附近区域水压力梯度较大,达0.046MPa/m,而在中间区域相对平缓,平均水压梯度约0.011MPa/m;在地热开采过程中,温度整体呈下降趋势,在生产井附近区域,温度呈非线性降低,与时间呈负指数关系下降趋势,而在注入井附近区域温度呈线性下降.

Coupled thermal-hydrologic-mechanical phenomena in fractured rock masses are studied with a model based on differential control equations.The nodal displacement and water pressure and temperature were estimated in the different media.The strategy and methods required to solve this mathematical model are discussed.A three dimensional finite element model was proposed.A detailed 3D simulation of work in hot dry rock 6000 meters below the surface was performed.At the beginning of operations,water in continuous rock ascends more slowly that water in the fractured medium.After one year,the water pressure is constant and hot water flows through a fixed pressure gradient.The gradient around the injection and production wells is larger,about 0.046 MPa per meter.But the average gradient is smaller,about 0.011 MPa per meter.As heat is extracted and the temperature of the rock decreases around the production well the temperature follows a negative exponential function.Near the injection well the temperature follows a linear function.A foundation for project selection and decisions regarding proper exploitation of hot dry rock was presented.