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

地下储氢被认为是支撑全球氢经济的可行方案之一。除了氢存储的操作挑战之外，解决UHS涉及的基本物理化学过程也是至关重要的。尽管UHS与天然气、压缩空气和二氧化碳地下储存有相似之处，但由于氢的物理和化学性质，它们有独特的区别。为了确保氢的安全和有效存储，需要研究以下过程：氢不溶于水，使浮力效应比二氧化碳和天然气强得多。氢和盐水密度的显著差异导致氢快速向上迁移并分离成不同的相。然而，由于氢的低粘度，它也可以横向扩散到更广泛的区域。当流体离开它被注入的地方时，流体速度下降，导致流动的前沿受到毛细管力的影响。在制氢阶段，可能会发生毛细管捕获，这会导致卤水在渗吸过程开始时留下氢气。同样，储集层非均质性的存在(岩性的不均匀分布)使得相对渗透率和毛管压力等动态特性变得非常重要。为了最大限度地减少由于上述不同流动复杂性而造成的氢气损失，我们将使用两相流模拟方法。这将包括实施简化模型，以了解UHS对储集层盖层完整性的长期影响。此外，还将利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气流动特性的有效性，如相对渗透率。项目的第一年主要关注氢气在含水层中的流动和传输。由于氢气比盐水轻得多，强大的浮力将氢气推向盖层。这将导致氢和卤水的快速分离和垂直方向上的静水压力分布。根据这一假设，我们利用了一种简化的油藏模拟方法，将维度减少了一维。因此，我们可以研究UHS以及微生物和地球化学等其他活动的长期影响。相对渗透率是氢气流动的一个贡献因素，因此有必要对其进行准确的测量。除了相对渗透率之外，气体粘度也是在有盐水存在的情况下氢气流动性的一个决定性参数。由于氢的迁移率比水高得多，在实验室尺度的测量中很有可能出现粘性指进效应。我们进行了实验室规模的模拟，以验证文献中报道的相对渗透率在现场尺度上是否可靠。氢可能是地下耗氢微生物生长的原因。枯竭或盐水储集层中的微生物活动可能对氢安全和储盖完整性构成威胁。有各种各样的微生物消耗氢，包括产甲烷菌、硫酸盐还原菌、产同乙酸菌和铁(III)还原菌。注射压力-温度条件、盐水pH值和底物供应是影响氢耗的基本因素。除了微生物活动造成的氢损失外，微生物还可以堵塞储集层的孔隙，导致储集层注水能力/生产率下降。为了全面了解微生物如何在水库水平上消耗氢气，有必要将流动模型与微生物反应模型相结合，并进行实验测试或采用新息模型。

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