层状盐岩储气库建腔期安全综合评价及多因素优化研究

发布时间：2018-08-30 09:31

【摘要】：由于盐岩具有水溶性、良好的蠕变性、损伤自恢复性、低渗透率以及塑性变形能力大等优良特性,并且盐岩洞室利用率高、占地面积小、瞬时吞吐量大、易开挖,国内外均采用盐岩储库作为能源储备介质。尽管盐岩储库相对于其他能源储备围岩体具有较好的安全性,但我国盐岩储备层与国外巨厚盐丘相比,具有盐岩品位低、夹层数目多、埋藏浅、岩层厚度薄等特点,并且建腔过程不可见,无法控制腔体形状;在卤水长期浸泡下,盐岩力学性质发生改变;不溶或难溶夹层的垮塌等都会对盐岩储气库建腔期的安全性造成威胁。盐岩储气库水溶建腔是一项复杂的系统工程,合理的选择建腔工艺及建腔方法才有可能得到设计的形态,包括淡水循环方式的选择、建腔管柱的组合方式、淡水注排量的确定、顶底板的保护措施、溶腔形状的检测、油垫位置的控制和配套的地面设备等。在建腔过程中只有这些问题得到正确合理的解决,才能使建成的溶腔符合储气库要求。由此可见,在建腔过程中会面临很多复杂问题,这会影响盐岩储气库建腔期的安全,因此,非常有必要对我国盐岩储气库建腔期进行安全性分析。本文研究的主要内容及研究成果如下:①分析了层状盐岩地下储气库水溶建腔原理及单井对流法水溶建腔工艺。介绍了影响盐类矿物溶解速度的主要因素,包括盐类矿物的品位、结构构造、水溶性、构成组分等内在因素和溶液浓度、运动状态、溶解面的空间位置、温度和压力、溶剂的性质等外在因素。②应用国内首款自主研发的层状盐穴建造过程的造腔软件(Salt Cavern Builder V1.0)对影响造腔的关键因素进行了模拟造腔分析,这些关键因素包括:循环方式、盐岩品位、注水排量、管柱组合、夹层数量及油垫位置。由造腔软件模拟的结果可以看出,如果造腔工艺选择不当,造出的腔体形状极不规则。③通过对层状盐岩地下储气库典型事故原因进行深入的分析,并结合金坛盐穴储气库实际地质条件和建腔过程中存在的影响因素,从盐岩与夹层特性、地层特征、腔体设计、施工控制、配套设施及人为失误六个方面来分析可能引起盐岩储气库建腔期事故的危险源,建立了层状盐岩储气库建腔期的事故树模型。通过对事故树进行定性分析,得到了可能导致建腔期事故发生的所有途径和基本致因事件。④对由事故树得到的危险因子进行合理筛选后按其性质不同进行归类,分为盐岩力学参数、夹层参数、建腔参数三个评价单元,建立了层状盐岩储气库建腔期安全评价体系。基于前人的实验研究及本课题组成员的数值模拟结果建立了安全评价体系的指标评分模型。⑤基于变权和相对差异函数对拟建M井盐岩储气库建腔期进行了安全综合评价。层次分析法得到的指标常权通过变权方法进行调整,得到的变权权重随评价值的改变而改变,能够突出个别指标评价值的明显变化对评价结果产生的影响,若个别指标的评价值得分很低,则经过变权处理后其权重将会有很大的提高。各个评价指标安全等级的隶属度由相对差异函数来确定,可以体现某些影响因素在评价体系中的重要性。将基于变权和相对差异函数法的安全评价结果与利用模糊综合评价法以及模糊灰关联评价法的评价结果进行对比分析,三者的级别特征值相差不大,证明变权和相对差异函数综合评价法具有良好的准确性和客观性。⑥针对层状盐岩储气库建腔期的三个可控因素:夹层位置(可以通过调整腔体埋深来实现)、腔体高径比、矿柱间距进行优化。夹层位置这一因素设置3个水平:1/4H、3/4H、1/2H,其中H为腔体高度;高径比这一因素设置三个水平:1.0D、1.5D、2.0D;矿柱宽度这一因素设置三个水平:1.0D,1.5D,2.0D,D为腔体直径。基于正交实验法确定实验方案,应用COMSOL Multiphysics软件对实验方案进行数值模拟,选取腔顶点、腔底点、腔腰点的应力和夹层所受的平均应力及腔顶点、腔底点、腔腰点和夹层的位移作为实验指标。将数值模拟得到的关键点的等效应力及位移进行极差分析和SPSS方差分析,确定了各个因素敏感性程度、最佳水平及最优组合方式。将得到的最优组合中的高径比和矿柱宽度的值带入到第四章的高径比和矿柱宽度的评分模型中,得分均为100,即为最佳水平,验证了数值模拟的准确性。
[Abstract]:Salt rock reservoirs are used as energy storage media at home and abroad because of their excellent properties such as water solubility, good creep, damage self-recovery, low permeability and large plastic deformation capacity, high utilization rate of salt rock caverns, small area occupied, large instantaneous throughput and easy excavation. Surrounding rock mass has better safety, but the salt rock reserve layer in our country has the characteristics of lower salt rock grade, more interbeds, shallow burial, thin rock thickness and so on, and the cavity construction process is invisible, unable to control the shape of the cavity; in the long-term brine immersion, the mechanical properties of salt rock change; insoluble or insoluble interbeds collapse. Salt rock gas storage cavern construction is a complex system engineering, reasonable selection of cavern construction technology and method is possible to get the design form, including the choice of freshwater cycle, the combination of cavity string, the determination of freshwater injection and displacement, roof and floor protection. Protection measures, cavity shape detection, oil cushion position control and supporting ground equipment, etc. Only when these problems are correctly and reasonably solved in the process of cavity construction, can the built cavity meet the requirements of gas storage. The main contents and achievements of this paper are as follows: (1) The principle of water-soluble cavity construction in layered underground gas storage and the technology of single well convection water-soluble cavity construction are analyzed. The main factors affecting the dissolution rate of salt minerals, including the grade of salt minerals, are introduced. The internal factors such as structure, water solubility, composition and solution concentration, movement state, spatial position of solution surface, temperature and pressure, and properties of solvent were simulated. The key factors include: circulation mode, salt rock grade, water injection and discharge, pipe string combination, number of interlayer and position of oil cushion. The simulation results show that the cavity shape is very irregular if the Cavity-making technology is not properly selected. 3. Through in-depth analysis of the typical accident causes of layered salt rock underground gas storage. Combined with the actual geological conditions of Jintan salt cavern gas storage and the influencing factors in the process of cavern construction, the paper analyzes the dangerous sources which may cause the accidents in the cavern construction period of the salt cavern gas storage from the aspects of salt rock and interlayer characteristics, stratum characteristics, cavity design, construction control, supporting facilities and human errors, and establishes the cavern construction of stratified salt rock gas storage. Based on the qualitative analysis of the fault tree, all possible approaches and basic causes of the accident during the cavity construction period are obtained. 4. The risk factors obtained from the fault tree are classified according to their different properties and are divided into three evaluation units, i.e. mechanical parameters of salt rock, interlayer parameters and cavity construction parameters. The safety evaluation system of layered salt rock gas reservoir during cavity construction period is established. Based on the previous experimental research and numerical simulation results of the members of this research group, the index scoring model of the safety evaluation system is established. _Based on variable weight and relative difference function, the safety evaluation of the proposed M well salt rock gas reservoir during cavity construction period is carried out. The index constant weight is adjusted by the variable weight method, and the variable weight is changed with the change of the evaluation value. It can highlight the impact of the obvious change of the evaluation value of individual index on the evaluation results. If the evaluation value of individual index is very low, the weight will be greatly improved after the variable weight treatment. The membership degree of the grade is determined by the relative difference function, which can reflect the importance of some influencing factors in the evaluation system. _According to the three controllable factors of the layered salt gas storage cavern construction period: the position of interlayer (which can be realized by adjusting the buried depth of the cavern), the ratio of height to diameter of the cavern, and the spacing between ore pillars are optimized. The interlayer position has three levels: 1/4H, 3/4H, 1/2. H, in which H is the cavity height; the ratio of height to diameter is set at three levels: 1.0D, 1.5D, 2.0D; the width of pillar is set at three levels: 1.0D, 1.5D, 2.0D, D is the cavity diameter. The stress and the average stress of the interlayer and the displacement of the apex, the bottom, the waist and the interlayer of the cavity are taken as the experimental indexes. The values of height-diameter ratio and pillar width are brought into the evaluation model of height-diameter ratio and pillar width in Chapter 4, and the scores are both 100, which is the best level, which verifies the accuracy of numerical simulation.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE88

【相似文献】