【作者】 黄远智；

【导师】 张楚汉；

【作者基本信息】 清华大学 ， 水利工程， 2006， 博士

【摘要】 低渗透岩石非线性渗流机理及其数值计算方法的研究是当前渗流力学研究的一个前沿课题,对水利工程、石油工业、矿山开采、废料填埋等国民生产有着重要的意义。本论文作为国家自然科学基金资助项目“低渗透弱胶结岩石非线性渗流机理研究”的一个组成部分,通过对低渗透岩石系列渗流实验结果进行深入研讨并结合数值分析的方法,对该课题开展了研究。基于岩样铸体技术和压汞实验获取的实验岩样孔隙结构参数,论文首先分析得出了低渗透岩石普遍存在的孔隙结构特征,以从微观结构的角度建立起岩石与其低渗透性表征以及非线性渗流之间的联系。分析以砾岩和砂岩为对象的单相饱和渗流实验表明,岩石低速渗流运动偏离了达西定律,且渗流曲线不通过坐标原点,岩石渗透率也随着压力梯度的变化而变化。论文通过数值拟合得到了拟合精度高的非线性饱和渗流运动方程,并从边界层的力学特征出发,揭示出了方程非线性项的物理意义,分析了边界层因素对形成非线性渗流的机理作用。非饱和渗流实验更为明显地表现出了低渗透岩石渗流的非线性特征。基于毛细管模型并结合边界层理论,论文推导了等径毛管非饱和渗流运动模型,得到了非线性渗流速度及启动压力梯度的解析式,从而对毛管压力在形成低渗透岩石非线性渗流的机理作用方面进行了论证。并且通过归纳实验现象发现,当岩体非饱和带中液体的饱和度不小于85%时,渗流的宏观运动特性接近于饱和渗流,可以采用与饱和渗流类似形式的运动方程进行描述。流固耦合渗流实验证明岩石具有弹塑性特征,应力历史对岩石渗透性能有着重要影响。在耦合渗流分析中,论文对岩石渗透率与有效应力的函数关系进行了研究,并运用岩石渗透率对有效应力敏感系数的概念,将复杂的渗流耦合影响因素进行归一化处理。通过分析求证了渗透率敏感系数与有效应力之间存在幂函数关系,并给出了基于敏感系数的渗透率与有效围压之间的函数关系式。在综合以上各项渗流实验结果的基础上,论文还通过渗流现象对比以及理论分析,对非线性渗流机理进行研讨,总体上将低渗岩石非线性渗流机理归纳为岩石的孔隙结构特点、流体性质及孔隙结构与流体之间相互作用等几个方面。根据非线性渗流运动规律的研究成果,论文建立了体现变渗透率的非线性渗流模型,提出了求解非线性渗流数值方程的变渗透率数值方法,开发了相应的计算系统,并用算例对模型及数值方法的可行性进行了说明。更多还原

【Abstract】 Non-linear seepage mechanics in low permeability rock and its numerical analytical method is one leading task of seepage research, which acts as an important role to hydraulic engineering, petroleum industry, mining project, waste landfill, and so on. This doctoral dissertation is pertaining to the research subject concerning the non-linear seepage mechanism in low permeability incompetent rock, which is supported by National Science Fund of China. The task mentioned above is studied in this dissertation by delving into the result of a series of seepage experiments and trying to find out some method for numerical analysis.Based on the parameters concerning pore structure of conglomerate and sandstone gathered from the rock body of casting and mercury penetration experiments, those stones from Shimenzi Reservoir, Xinjiang province and from Changqing oil field Gansu province respectively are taken as samples in this regards. The common pore structural feature of these low permeability rock is concluded at first, which could be deemed to set up the relation between rock and its low permeability feature as well as non-linear seepage phenomena within.It is revealed by the saturated single liquid seepage experiment performed by FDES-641 triaxial system that the movement of low speed seepage in low permeability media departs from the law of Darcy, meanwhile the curve of seepage flow would not pass through the origin of coordinates. Permeability of rock changes with the pressure gradient either. Non-linear seepage formula with high fitting accuracy is achieved by the method of numerical analysis. Starting from the point of the mechanical characteristics of boundary layer, the physical meaning of the non-linear term in formula is revealed, meanwhile the mechanics towards non-linear seepage flow but caused by boundary layer is concluded.Unsaturated seepage experiments in low permeability rock present more obvious non-linear seepage characteristics. One numerical model of unsaturated seepage flow in constant diameter capillary is established based on the simplified model of capillary and the theory of boundary layer, meanwhile the analysis formulas of seepage velocity and threshold gradient of non-Darcy seepage flow are deduced accordingly. The mechanics towards non-linear seepage flow but caused by capillary pressure is analyzed by this way. When summing up the unsaturated experimental phenomena above, it can be concluded that the macroscopical movement characteristics of unsaturated seepage flow would behave much close to that of the saturated infiltration when the degree of liquid saturation in rock comes up to 85%. Similar formula used to describe the movement of saturated seepage can also be applied to characterize the unsaturated flow in this regard.It is proved by the liquid-solid coupling seepage experiment that rock owns elastoplasticity, loading would bring rock with plastic deformation beyond retrieve, and the loading history would play a significant effecting role in the change of permeability of rock. The functional relationship between the permeability and the effective confirming pressure is analyzed through experiment. Due to great complexity of the coupling factors affecting the permeability of rock, the coefficient of sensitiveness between the permeability of rock and the effective pressure is defined accordingly as to generalize those factors. Power function can be used to describe the relation between the permeability of rock and the effective pressure based on the coupling seepage experiments, and the function between the permeability of rock and the effective pressure but based on the conception of coefficient of sensitiveness is established hereafter.With the help of not only the summary of the experimental findings mentioned above, but also some further contradistinctive experiments together with some corresponding theoretical deduction as well, the mechanics towards non-linear seepage flow are delved into and totally classified into three categories, those are, the pore characteristics of rock, the feature of liquid and the interaction between liquid and rock.According to the research findings of non-linear seepage flow, one variable permeability non-linear seepage numerical model is established in this dissertation. The corresponding solution for the non-linear equation is developed either. Calculation program based on the model is developed hereby and the feasibility of the non-linear model as well as its solution is illuminated by the designed examples.更多还原