【作者】 徐素国；

【导师】 赵阳升； 梁卫国；

【作者基本信息】 太原理工大学 ， 采矿工程， 2010， 博士

【摘要】 基于西气东输工程,急需东部地区建造地下盐岩矿床储气库。由于我国盐矿床有单层厚度薄(60～100m)、软弱夹层多的地质特点,使油气储库建造的难度和复杂程度有所增大,与国外普遍利用深部盐丘建造油气储库的实践有很大的不同,同时夹层使油气储库的运行的稳定性方面有很大影响,急需层状盐岩矿床油气储库稳定性分析基础性的资料以及建造理论,对现场实践提供技术支持。本文以在层状盐岩矿床中以水溶建腔方式建造油气储库为背景,通过实验研究与理论分析相结合,数值分析与相似模拟相结合的方法,研究了与油气储库建造相关的盐岩溶解特性以及与含夹层储气库稳定性相关的盐岩力学特性,包括反复应力及应变率对夹层和盐岩的力学特性影响作用;对含夹层盐岩体的破坏方式进行了研究,并运用Fluent软件模拟研究了两种形状盐岩溶腔流场的运动形态及分布,对圆柱形溶腔内流场运移情况在实验室进行模拟。主要研究内容及结果如下:(1)溶解角度对岩盐溶解速率产生较大的影响,向上斜溶即-45°溶解角度下溶解速度最大。溶蚀角由-45°、-90°、0°、45°、至90°,盐岩的溶解速率逐步降低。-45°溶解角度下的溶解速率3 g /cm~2*h比90°溶蚀角的0.5g /cm2*h溶解速率高6倍。钙芒硝盐岩的溶解速率比90°溶解角度下的溶解速率低三个数量级,属于极难溶盐类。(2)石膏干试件的平均极值强度为12.3MPa,盐水浸泡后,在反复加卸载作用下,石膏的强度并未降低,但是,在盐溶液中浸泡之后试件变形能力增强。含盐分泥岩与自然泥岩在强度上相当,无论在清水和饱和盐水中溶浸后,实验表明在20天的浸泡时间内,其强度和弹性模量都没有明显降低。(3)含夹层盐岩由于两种岩体的泊松比不同,导致横向变形不一致,在层状岩体交界面附近的岩块中产生的水平方向的附加应力,该附加应力使此处由单轴应力变为三轴应力状态。其中,弹性模量较大、泊松比较小的岩块变为三向压—拉应力状态;而弹性模量小、泊松比大的岩块变为三向压应力状态。层状岩盐的破坏形式上表现为:岩盐部分产生拉伸裂纹,表现为柱状劈裂;夹层部分为压拉破坏,表现为环状由外向内的锥形剪裂。在单轴应力-应变曲线上所表现为应力反复现象。(4)在循环加卸载作用下,芒硝盐岩试件强度有明显降低,卸载过程的杨氏模量略高于加载过程中的杨氏模量。加卸载过程中盐岩及含夹层盐岩杨氏模量随应力水平及加卸载次数的变化很小,初期循环加卸载曲线基本呈线性并重叠,随应力水平及循环次数的提高,滞回环现象才有轻微表现,但滞回环面积非常小.(5)岩盐试件的强度基本不受加载应变速率的影响,弹性模量随应变速率的增高略显增大,但增幅较小。盐岩的泊松比均随加载应变速率的增大而减小,表明横向变形能力减弱。随加载应变速率的增大,试件在应力达到峰值时的应变减小,其变形模量与加载应变速率呈对数关系:E 0 = 0.2Ln(ε?)+3.2(6)在单层岩盐矿床内,利用定向对接连通控制水溶开采技术,建造储库溶腔。储库断面形状近似圆形或椭圆形,断面直径约40～50m(小于矿床单层厚度),水平向长度根据地质条件在500～1000m范围内。穿越夹层建造储气库优化方法的基本宗旨是,合理选择循环方式,运用混合建腔方法,实时调整中心管与中间管的位置,采用混合建腔方法。(7)以圆形溶腔为例进行数值模拟,分析得出储气库腔体半径小于30m建造阶段,油垫位置距注水口距离小于腔体半径(i<1)的条件下,腔壁附近流体运移平均速度随两管口间距的增大而非线性减小,两管口间距理想值可取20-30m;当油垫位置距注水口距离大于腔体半径(i≥1)时,两管口间距理想值>30m。(8)结合物理模拟与数值模拟结果分析,要加快腔壁盐岩的溶解及提高整个储气库建造速度,当腔体半径较小时,管柱间距不宜过大;当腔体半径超过30m后,可增大两管口距(40m以上);另外,将注水管口的垂向出水改为小口径多孔水平射流,可极大提高腔壁附近溶质的对流,加快盐岩的溶解,提高储气库建造速度。更多还原

【Abstract】 For West-East Natural Gas Pipeline Project, it should build the underground oil and gas storage cavern in the bedded salt rock deposit in eastern China. As the salt deposits have geologic characteristic of monolayer thickness and flabbiness interlayer in China, it is difficult to build the storage cavern in the salt rock deposit. It is also different from building the storage cavern by the salt dome in the foreign countries. Meanwhile, the interlayer has great influence on the building and stability of the storage cavern. Therefore, it needs fundamental data and building theory on the stability of the storage cavern in the bedded salt rock deposit to provide technical support for the practice.Based on building the storage cavern in the bedded salt rock deposit by the water-soluble building cavity, the paper combines the experiment with the theory analysis, the numerical analysis with the similar simulation to study the soluble property of the rock salt which is related to the building of the storage cavern and the mechanical property of the rock salt which is related to the stability of the storage cavern with interlayer, including the influence of the repeated stress and the strain rate on the interlayer and the mechanical property of the salt rock, and on the failure style of the rock salt with interlayer. Furthermore, it also uses FLUENT software to study the flow field running style of two kinds of the shape salt cavern and simulate the flow field style of the column salt cavern in the laboratory.The following are the main research contents and results:(1) The dissolved angle has great effect on the dissolution rate of the rock salt. The dissolution rate is the fastest if the inclined solution angel is -45°upwards. The dissolution rate in -45°is 3 g /cm2*h, which is 6 times faster than that in 90°(0.5g /cm2*h). The glauberite dissolution rate is three grades lower than that of 90°, which belongs to the difficult dissolution salt.(2) The average peak strength of gypsum dry specimens is 13.3MPa. After saturated in brine and the repeated loading and unloading, the strength of gypsum does not fall. However, the ability of deformation of the specimens after saturated in brine is enhanced. The strength of salt-mudstone is the same as that of mudstone, either dipping in water or brine. The experiment shows that strength and modulus of elasticity have no change in twenty-day dipping.(3) Due to the different Poisson’s ratio in the rock salt with interlayer, it results in inconsistencies of the horizontal deformation. The additional stress in the horizontal direction near the interface of rock mass makes the uniaxial stress into the triaxial state of stress. The rock mass with larger elastic modulus and smaller Poisson’s ratio becomes into the state of three-dimensional pressure-tensile stress while the rock mass with smaller elastic modulus and bigger Poisson’s ratio becomes into the state of large compressive stress. The failure style of rock salt with interlayer shows tensile cracks in the part of the rock salt, i.e. the columnar fracture; the part of the interlayer shows pressure pulling failure, i.e. cone-shaped ring from outside to inside shear rupture. It shows stress repetition on the uniaxial stress-strain curves.(4) Influenced by the cyclic loading, the strength of Glauber’s salt is greatly reduced. The Young’s modulus in the unloading process is a little bit higher than that in the loading process. The Young’s modulus of the rock salt and the rock salt with interlayer change little with the stress levels and the loading and unloading times in the loading and unloading process. The initial cycle of loading and unloading curve is linear and overlapping. With the stress levels and the cycle times improving, the hysteresis loop can slowly show, but the hysteresis loop area is very small.(5) The loading strain rate has few effects on the strength of the rock salt. The elastic modulus increases slightly with the increasing strain rate, but it is comparatively smaller increase. The Poisson’s ratio of the rock salt decreases with the increasing strain rate, which indicates that the ability of the lateral deformation diminishes. With the loading strain rate increasing, the strain decreases when the stress reaches the peak. The deformation modulus has logarithmic relation with the strain rate loading: E 0 = 0.2Ln(ε?)+3.2(6) In the single-layer rock salt deposits, the directional control connectivity dissolution mining techniques is used to build cavern. The shape of cavern is similar to oval or quasi-circular. The diameter is about 40-50m (less than the deposit thickness of single layer) and the horizontal length ranges from 500m to 1000m according to the geological conditions. The main idea of building cavern through interlayer is that circulation way should be reasonably selected, and mixed-built cavern methods are combined to real-timely adjust the position between the central tube and the intermediate tube.(7) The circle melting cavity is made as an example to do numerical simulation. It is studied that when cavity radius is less than 30m and the oil pad location is nearer than the distance from the injection port cavity radius (i <1), the moving rate of the fluid flow near the wall increases with the distance between two mouth of the tube which is ideally 20 ~ 30m.When the distance between the oil pad location and the injection hole is bigger than that of the cavity radius (i≥1), the ideal distance of two mouth can more than 30m.(8) After the analysis of combining the physical modeling with the numerical simulation, it is known that in order to speed up the dissolution of the salt near the cavern wall or the building of the whole cavern, the distance between two mouth of the tube should not be large when the cavern radius is smaller; the distance between two mouth of the tube can be increased (>40m) when the cavern radius is more than 30m. In addition, the out water mouth can be adjusted to vertical small-caliber porous jet to greatly improve the parietal near the solute convection and speed up the dissolution rate of the rock salt and the building of the cavern.更多还原