Caprock -Reservoir Integrity of Subsurface Storage of Hydrogen (CRISTHY)

地下储氢（UHS）已被推广为支持全球氢经济的可行解决方案之一。除了储氢的操作挑战外，解决UHS中涉及的基本物理化学过程也至关重要。虽然UHS与天然气、压缩空气和CO2地下储存之间存在相似之处，但由于氢的物理和化学性质，它们之间存在独特的差异。为了确保氢气的安全和有效储存，需要研究以下过程氢气不溶于水，浮力效应远强于二氧化碳和天然气。氢气和盐水之间的密度差异导致氢气快速向上迁移并分离成不同的相态。然而，由于其低粘度，氢气也可以横向扩散到更宽的区域。随着流体远离其被注入的位置，流体速度降低，导致流体的前部被毛细力所包围。在制氢阶段期间，可能发生毛细管捕获，这可能导致盐水由于开始渗吸过程而留下氢。（岩石性质的不均匀分布）使得相对渗透率和毛细管压力等动态性质变得非常重要。为了最小化由于上述不同流动复杂性而导致的氢损失，我们将利用两相流模拟方法。这将包括实施简化模型，以了解UHS对储层盖层完整性的长期影响。此外，还将采用复杂的两相流模拟方法，研究储层非均质性和流体性质对注氢能力和产能的影响。数值模型也将被用来验证测量的氢流动特性的有效性，例如相对渗透率。该项目的第一年主要关注氢在含水层中的流动和运输。由于氢比盐水轻得多，强大的浮力将氢推向盖层。这将导致氢气和盐水的快速分离以及垂直方向上的静水压力分布。利用这一假设，我们已经利用了一个简化的油藏模拟方法，减少了一个维度的数量。因此，我们可以研究UHS和其他活动（如微生物和地球化学）的长期影响。相对渗透率是氢流量的一个影响因素，因此其准确测量是必要的。除了相对渗透率外，气体粘度也是盐水中氢迁移率的一个决定性参数。由于氢的迁移率比水高得多，在实验室规模的测量中，粘性指进效应的可能性很高。我们进行了实验室规模的模拟，看看文献中报道的相对渗透率在现场规模上是否可靠。氢可能是地下耗氢微生物生长的主要原因，微生物在衰竭或盐水储层中的活动会对氢安全和储层-盖层的完整性构成威胁。存在多种消耗氢的微生物，包括产甲烷菌、硫酸盐还原菌、同型产乙酸菌和铁（III）还原菌。注入压力-温度条件、盐水pH值和底物供给是影响氢耗的重要因素。除了由于微生物活动引起的氢损失之外，微生物还可以堵塞储层的孔隙，导致储层注入能力/生产能力的降低。为了全面了解微生物在储层水平上如何消耗氢，有必要将流动模型与微生物反应模型结合起来，并进行实验测试或采用孔隙尺度模型

Underground hydrogen storage (UHS) has been promoted as one of the feasible solutions to support the global hydrogen economy. In addition to the operational challenges in hydrogen storage, addressing the fundamental physical-chemical processes involved in UHS is crucial. Although there are similarities between UHS and natural gas, compressed air, and CO2 subsurface storage, there are unique differences due to the physical and chemical properties of hydrogen. To ensure the safe and efficient storage of hydrogen, the following processes need to be investigated Hydrogen does not dissolve in water, making the buoyancy effects much stronger than CO2 and natural gas.The significant difference in density between hydrogen and brine causes hydrogen to migrate upwards quickly and separate into different phases. However, hydrogen can also spread laterally over a wider area due to its low viscosity. As the flow moves away from where it was injected, the fluid velocity decreases, causing the front of the flow to becomedominated by capillary forces. During the hydrogen production stage, capillary trapping may occur, which can cause the brine to leave behind hydrogen due to the start of the imbibition process.Likewise, the presence of reservoir heterogeneity (Non uniform distribution of rock properties) makes dynamic properties like relative permeability and capillary pressure very important.In order to minimise the hydrogen loss due to the different flow complexity mentioned above, we will utilise two-phase flow simulation methods. This will include the implementation of simplified models to understand the long-term impact of UHS on reservoir caprock integrity. In addition, the complicated two-phase flow simulation method will be used to study the effect of reservoir heterogeneity and fluid properties on hydrogen injectivity and productivity. Numerical models will also be used to verify the validity of the measured hydrogen flow properties, such as relative permeability.The project's First yearis mainly focused on the flow and transport of hydrogen in aquifers.As hydrogen is much lighter than brine, strong buoyancy forces pushhydrogen to the caprock. This would lead to fast segregation of hydrogen and brine and hydrostatic pressure profile in the vertical direction. Using this assumption, we have utilised a simplified reservoir simulation method that reduces the number of dimensionsby one. Therefore, we can investigate the long-term effect of UHS and other activities, such as microbial and geochemical.Relative permeability is a contributing factor in hydrogen flow, so its accurate measurement is necessary. In addition to relative permeability, gas viscosityis a defining parameter in hydrogen mobilityin the presence of brine. As hydrogen mobility is much higher than water, there is ahigh probability ofviscous fingering effect at labscale measurements.We have conducted lab-scaled simulations to see whether the reported relative permeability in the literature is reliable on the field scale. Hydrogen may be responsible for the growth of hydrogen consuming microbes in the subsurface.Microbial activity inside depleted or brine reservoirs can pose a threat to hydrogen security and also reservoir-caprock integrity. There are a variety of microorganisms that consume hydrogen, including methanogens, sulfate reducers, homoacetogenic bacteria, and iron (III)reducers. The injection pressure-temperature condition, pH value of brine, and substrate supply are essential factors affecting hydrogen consumption. In addition to hydrogen loss due to microbial activity, microorganisms can also plug the pores of the reservoir, leading to a decrease in reservoir injectivity/productivity. In order to gain a comprehensive understanding of how microbes consume hydrogen at a reservoir level, it is necessary to integrate flow models with microbial reaction models and conduct experimental tests or employ porescale modelling