二氧化碳盐水层封存的数值模拟研究

发布时间：2018-05-13 05:21

本文选题：CO_2盐水层封存 + 数值模拟　；参考：《中国科学技术大学》2015年硕士论文

【摘要】：CO2排放量的大量增加加剧了温室效应,导致全球变暖、冰川融化、海平面上升等一系列环境问题,碳捕获与封存是目前最具前景的实现大规模减排CO2的措施之一。盐水层分布广泛、容量巨大等优势使得盐水层成为最受关注的CO2封存地点。在一般选定的注入地层中CO2注入后以超临界状态存在,超临界状态的CO2密度大、粘度低、流动性好等特点有利于CO2在盐水层中的封存。注入到盐水层的CO2首先会进入岩石的孔隙之中,随着时间的推进,CO2会在浮力的作用下往上运动,直至遇到盖层。随后CO2将与盐水、岩石发生一系列物理化学反应,通过包括构造封存、残余气封存、溶解封存、矿化封存在内的多种机理实现封存CO2的目的。本文以CO2盐水层封存为研究对象,基于多相流体力学、渗流力学、计算流体力学等多学科的基础理论知识,采用数值模拟的方法,在建立数学模型后研究了注水对CO2分布及溶解的影响和CO2在深部盐水层发生泄漏迁移至浅水层时CO2的分布及泄漏的修复措施。对于注水对CO2分布和溶解的影响的研究,本文通过考察在不同注水模式、注水速率、注水位置、盐度和孔隙度等参数下CO2的溶解行为,系统地分析了注水对CO2溶解的影响,探讨了通过注水促进溶解封存、提高CO2封存安全性的措施。研究结果表明,注入CO2后,超临界态CO2成倒锥形聚集分布于注入井附近的盐水层顶部,分布半径随时间缓慢增大。注水虽不会引起CO2分布的明显变化,但可显著促进CO2的溶解。增大注水速率、靠近盐水层顶部注水以及在注CO2过程中同时注水均可提高CO2的溶解率。另外,CO2的溶解行为还可能会在不同水文地质参数条件下发生一定变化。CO2的溶解量随盐水盐度的降低而提高,但几乎不随岩石孔隙度变化。这些研究结果揭示了盐水层中CO2的溶解行为,可为发展安全可靠的CO2封存技术提供参考依据。对于CO2在深部盐水层发生泄漏迁移至浅水层时CO2的分布及泄漏修复措施的研究,本文通过考察不同泄漏场景下CO2的分布、压力分布以及采出井的采出速率、注水井的溶解效率以及参数的影响,系统地分析了泄漏的修复措施。模拟结果表明,CO2泄漏后,泄漏羽流分布于泄漏井附近的区域内,气相饱和度Sg沿径向和轴向往外逐渐降低,呈梯形分布；压力变化的等值线在CO2的泄漏羽流区域的分布是倾斜的,而在离泄漏羽流较远区域的压力变化的等值线是竖着分布的。注水可促进CO2的溶解,降低水相中CO2的浓度,越大的注水速率CO2溶解得越快。利用采出井可以采出流体可以达到减少或移除CO2的目的。用直井采出流体时,直井越深、直井竖直距离泄漏点越近、直井水平距离泄漏点越远,CO2采出速率越高；用水平井才出流体时,水平井设置在z向距离泄漏点越近处,CO2采出速率越高。地质参数影响着CO2的迁移和溶解,对CO2采出速率也存在一定影响。渗透率增大,CO2采出速率降低；孔隙度减小,CO2采出速率越小。这些研究结果揭示了浅水层中CO2的泄漏行为以及不同修复措施的影响,可为发展安全可靠、高效的CO2泄漏修复技术提供参考依据。
[Abstract]:A large increase of CO2 emissions intensifies the greenhouse effect, resulting in a series of environmental problems, such as global warming, melting glaciers and rising sea level. Carbon capture and storage are one of the most promising measures to achieve large-scale emission reduction of CO2. The saltwater layer is widely distributed and the capacity is huge, which makes the saltwater layer become the most concerned CO2 storage site.
In the general selected injection strata, the CO2 injection is present in the supercritical state. The CO2 density of the supercritical state is large, the viscosity is low, and the fluidity is good for CO2 in the salt water layer. The CO2 will first enter the pore of the rock, and as the time advances, the CO2 will move up under the action of buoyancy. The CO2 will then have a series of physical and chemical reactions with brine and rock, and the purpose of sequestration of CO2 is achieved through a variety of mechanisms including structural sequestration, residual gas sequestration, dissolution sealing, and mineralization sealing.
In this paper, based on the basic theoretical knowledge of multiphase fluid mechanics, seepage mechanics and computational fluid mechanics, CO2 saltwater layer sealing is based on the numerical simulation method. After establishing the mathematical model, the influence of water injection on the distribution and dissolution of CO2 and the distribution of CO2 when the leakage of the deep brine layer is migrated to the shallow water layer by CO2 is studied. And the repair measures of the leakage.
In the study of the effect of water injection on the distribution and dissolution of CO2, the dissolution behavior of CO2 under different water injection modes, water injection rate, water injection position, salinity and porosity is investigated. The effect of water injection on the dissolution of CO2 is systematically analyzed, and the measures to improve the security of CO2 sequestration by water injection are discussed. It is shown that after the injection of CO2, the conical aggregation of the supercritical CO2 into the top of the saltwater layer near the injection well increases slowly with time. The water injection will not cause the obvious change of the CO2 distribution, but it can significantly promote the dissolution of the CO2. The water injection rate is increased, the water injection near the top of the brine layer and the simultaneous injection of water in the process of CO2 injection can be raised. The dissolution rate of high CO2. In addition, the dissolution behavior of CO2 may also change under the conditions of different hydrogeological parameters. The dissolution of.CO2 increases with the decrease of salinity of brine, but it does not change with the porosity of the rock. These results reveal that the dissolution of CO2 in the saltwater layer is a safe and reliable CO2 sequestration technology. Provide reference basis.
In this paper, the distribution of CO2 and the repair measures for the leakage of CO2 when the deep brine layer is leaked to the shallow water layer are studied. In this paper, the distribution of CO2, the pressure distribution and the recovery rate of the well, the dissolving efficiency of the well and the influence of the parameters are investigated in this paper. After CO2 leakage, the leakage plume is distributed in the area near the leaky well, and the gas saturation Sg decreases gradually along the radial and axis yearning, showing a trapezoid distribution; the distribution of the equivalent line of pressure variation in the leaked plume region of the CO2 is tilted, and the equivalent line of pressure variation in the far region from the leaked plume is vertical. Water injection can be used. To promote the dissolution of CO2 and to reduce the concentration of CO2 in the water phase, the larger the water injection rate CO2 dissolves, the faster it can be dissolved. Using a mining well, the fluid can be obtained to reduce or remove CO2. When the fluid is produced in a straight well, the deeper the vertical well is, the closer the vertical distance leaking point is, the farther the horizontal distance leaking point is, the higher the CO2 recovery rate is, the higher the production rate is, the higher the production rate of the CO2, the higher the level of the recovery is, the higher the level of the recovery is, the higher the recovery rate of the vertical well; When the well is out of fluid, the higher the level of the horizontal well is at the nearer the Z to the distance leaking point, the higher the recovery rate of the CO2. The geological parameters affect the migration and dissolution of CO2, and also have a certain effect on the CO2 recovery rate. The permeability increases, the CO2 production rate decreases, the porosity decreases, the CO2 extraction rate is smaller. These results reveal the leakage of CO2 in the shallow water layer. Leakage behavior and influence of different repair measures can provide reference for developing safe, reliable and efficient CO2 leakage repair technology.

【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ116.3;TQ021.1

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