【作者】 时洪斌；

【导师】 刘保国；

【作者基本信息】 北京交通大学 ， 岩土工程， 2010， 博士

【摘要】 摘要：为了对水封式地下储油洞库群进行稳定性分析评价,从水封系统和洞库群围岩稳定性两方面进行研究。水封系统的研究在总结论述水封实验室试验的基础上,通过数值模拟和参数设计得到了水封泄漏的机理,优化了各水封参数的选取；洞库群围岩稳定性研究通过复杂模型的三维数值模拟,得到了水封条件下围岩稳定评价的各指标值,优化了洞库群的施工布置和开挖方案。具体研究内容如下：(1)在充分分析库区工程地质条件的前提下,以最大位移值为试验指标,通过正交试验确定了围岩力学参数的值和权重关系,结果表明围岩的弹性模量是影响最大位移值的最重要因素,其次是泊松比和内摩擦角,而抗拉强度和粘聚力影响最弱。在确定了围岩力学参数的基础上,分别以最大位移值、塑性区体积和拱顶垂直水力梯度为试验指标,通过正交试验确定了洞库的几何参数。另外根据库区提水试验结果和公式计算,得到了水文地质参数。(2)通过分析库区应力场和渗流场特征,建立了用于储库应力场与渗流场耦合作用分析的孔隙型等效连续介质数学模型,并给出了有限元法和有限差分法求解步骤。(3)在总结分析水封洞库泄漏实验室试验及微观机理的基础上,为了模拟储库的油气泄漏情况,采用非饱和地下水流及热流运移程序TOUGH2的TMVOC模块,进行了四种不同储油条件下的数值模拟,油品采用LPG(丙烷)。模型在TOUGH2_TMVOC的图形化界面程序PETRASIM中建立,分为无水幕和有水幕两种情况。数值模拟结果表明人工水幕系统可以十分有效地防止地下储油库的泄漏,保证气密和液密条件；在围岩饱和的情况下,即便是存在高导水率的大裂隙和断层(小于围岩渗透率的102倍),由于其处于饱和状态下,可以有效地阻止油气的泄漏,所以确保围岩水饱和是防止储库泄漏的前提条件；在人工水幕系统突然失效的极端情况下,油气会经过一定时间而不会立即泄漏至地表层。(4)针对自然地下水水动力封存和人工水幕水动力封存两种水封情况,分别进行了水封参数的分析。引入了衡量储库泄漏程度的泄漏参数Ψ评价自然地下水水动力封存,用以判断自然条件下储库的水封条件,并分析了储库几何参数对Ψ值的影响；采用最小水幕超压值评价人工水幕水动力封存,用以判断储库的水封条件。针对水幕覆盖范围、水幕超压、最大水幕压力、水幕钻孔间距、钻孔方向、储库与水幕间距等设计参数,给出了实际设计中的一些经验准则。在完全水封的情况下,以储库的临界储压为指标,采用有限元法从洞室几何参数、水幕布置和储库埋深三个方面对储库的储存能力进行了分析评价。在考虑应力场和渗流场耦合的情况下,分析了人工水幕系统对储库渗流场的影响并给出了估算储库涌水量的解析方法。(5)为了对洞库群进行耦合条件下的围岩稳定性分析,通过Solidworks, Hypermesh和FLAC3D等数值模拟软件建立了能够体现洞库群各部分特征的复杂三维数值模型,在FLAC3D中分别进行不考虑和考虑渗流场条件下的开挖模拟,以及耦合工况下的储油模拟。选取三个水平联络巷位置的横断面作为特征断面,从特征断面的应力场、位移场、水力梯度场和塑性区分布特征对模拟结果进行了分析评价。为了确定储库最优的洞群布置和单洞开挖方案,使得储库具有较高的稳定性,分别对洞群开挖工序和单洞开挖工序进行了方案比较,以塑性区体积和最大水平位移为评价指标得到了最优的开挖方案。数值模拟结果表明：在模型现有的力学参数、洞室几何参数、水封条件和边界条件前提下,储库可以实现完全水封,并且储库围岩是稳定的。(6)从地下水封储库的密闭性、围岩稳定性和可用性三个方面分别提出了评价指标。通过储库围岩水压力场和水力梯度场的分布来评价储库的密闭性。其涉及到的评价指标主要有：泄漏参数,降水漏斗范围,水幕超压值,临界储压,水力梯度,涌水量,气体饱和度,液态油品饱和度及溶于水油品质量分数等。通过应力场、渗流场、位移场和塑性区分布来评价储库的围岩稳定性。其涉及到的评价指标主要有：最大主应力、最小主应力、剪应力、最大位移和塑性区体积等。通过对储库的储油工况进行油品长期泄漏模拟和围岩流变模拟来评价储库的可用性。主要涉及到水封失效和围岩的粘塑性变形破坏,可以综合利用储库密封性和围岩稳定性的评价指标对储库进行可用性评价。更多还原

【Abstract】 In order to analyze and evaluate the stability of water sealed underground petroleum storage caverns, the efficiency of water curtain system and the surrounding rock stability of storage caverns are studied respectively. Several typical laboratory tests are summarized and refined. Through numerical modeling and parameter designing, the mechanism of petroleum leakage is clarified and all related water seal parameters are optimized. The study for surrounding rock stability is carried out through establishing and computing complicated three-dimensional numerical model. And then the value of each indicator for evaluating the surrounding rock stability is achieved, the layout and excavation scheme of storage caverns is optimized. The detailed terms of the study are as follows:(1) After clarifying the engineering geological conditions of storage caverns thoroughly, the orthogonal experiment for determining the values and the weights of mechanical parameters for surrounding rock was carried out with the maximum displacement as test index. The test results reveal that the most important element which affects the maximum displacement is elastic modulus, the next most important elements are Poisson ratio and internal frictional angle, and then tensile strength and cohesive strength take the third place. On the basis of qualified mechanical parameters for surrounding rock, more orthogonal tests were carried out to achieve appropriate geometric parameters, and the maximum displacement, the volume of plastic zone and the vertical hydraulic gradient were taken as test indexes respectively. In addition, hydrogeological parameters were attained according to the result of water lifting test and empirical formula.(2) In accordance with the characteristics of stress field and seepage field, porous equivalent continuum mathematical model was formed for resembling coupled stress field and seepage field. And the calculation procedures of finite element method and finite difference method for the mathematical model were provided.(3) On the basis of summarizing and refining several typical laboratory tests about leakage of water sealed storage caverns, the principle of petroleum leakage was put forward. TOUGH2_TMVOC was employed to resemble the leakage of storage caverns. Propane was taken as petroleum for modeling and four different storage conditions were studied. By making use of PETRASIM, two models for the condition without water curtain and the condition with water curtain were established respectively. The results indicate the following:The artificial water curtain system can retard or prevent leakage of petroleum storage caverns effectively. By operating with appropriate pressure and layout, the gas tightness and water tightness can be ensured. Along highly conductive features such as major fissure and faults (less than 102 times rock permeability), even partially saturated zones possess certain effects that can retard or prevent petroleum leakage, while a fully unsaturated major fissure or fault connected to the storage caverns can quickly cause petroleum leakage. This possibility strongly suggests that ensuring water saturation of the surrounding rock is a very important requirement. Even if an accident should suddenly impair the water curtain, the gas plume of the petroleum does not instantly penetrate the ground surface, the results of numerical simulations reveal that the gas plum takes several years to reach the ground surface.(4) The analytic evaluation for hydrodynamic containment based on natural groundwater or artificial water curtain was carried out respectively, and the related evaluation indexes were brought forth. The leakage parameterψwas introduced to evaluate the efficiency of hydrodynamic containment based on natural groundwater. Meanwhile the influence of geometric parameters on the value ofψwas examined. In order to evaluate the efficiency of the hydrodynamic containment based on artificial water curtain, the minimum overpressure of water curtain was employed. Some empirical rules for the design parameters in practice were put forward. And the design parameters mainly included the coverage and the overpressure of water curtain, the maximum water curtain pressure, the distance between drill holes, the direction of drill holes, and the distance between the roof of caverns and water curtain. Providing that air tightness and water tightness of storage caverns were ensured, the storage capacity of caverns was studied by employing finite element method. The study employed the critical storage pressure as indicator, the geometric parameters of caverns, the layout of water curtain and the depth of storage caverns as impact factors. On the condition of coupled stress field and seepage field, the impact of artificial water curtain on seepage field of surrounding rock was analyzed and the analytical method for estimating the water inflow of storage caverns was put forward.(5) Complicated three-dimensional numerical model with the characteristics of storage caverns was established by software of Solidworks, Hypermesh and FLAC3D. The aim was to analyze the stability of surrounding rock on the condition of coupling stress field and seepage field. Following that simulations for excavating condition with seepage field and without seepage field, and simulation for storing condition were implemented. Three cross sections of connecting tunnels located at three different levels were taken as feature sections. According to the characteristics of stress field, displacement field, hydraulic gradient field and distribution of plastic zone, the results of simulation were studied. In order to ensure optimized schemes for the layout of caverns and the excavating procedure of each cavern, and high stability of surrounding rock, the comparison of schemes was executed with the volume of plastic zones and the maximum horizontal displacement as evaluating indexes. The results reveal that under the current situations of mechanics parameters, geometric parameters, water seal conditions and boundary conditions, the air-water tightness and surrounding rock stability can be ensured.(6) In accordance with the air-water tightness of hydrodynamic containment system, the stability of surrounding rock and the usability of storage caverns, the corresponding evaluating indicators were put forward respectively. The air-water tightness was evaluated through studying the distribution of pore pressure and hydraulic gradient. The evaluating indicators for tightness were composed of leakage parameter, coverage of groundwater depression cone, overpressure, critical pressure, hydraulic gradient, water inflow, gas saturation, oil saturation and mass fraction of dissolved petroleum in water. The stability of surrounding rock was evaluated through analyzing the distribution of stress field, seepage field, displacement field and plastic zone. The evaluating indicators connected to stability included major principal stress, minor principal stress, shear stress, maximum displacement and volume of plastic zone. The usability of storage caverns was evaluated by simulating the long-time leakage and the rheology of surrounding rock. The usability was concerned with the ineffectiveness of hydrodynamic containment and the viscoplastic deformation of surrounding rock, which can be evaluated comprehensively by making use of the indicators for tightness and stability.更多还原