CO2 - H2 Optimisation in Rocks for Underground Storage (CHORUS)

英国准备采用净零碳排放技术，以实现其《巴黎协定》的目标，包括与氢（H2）燃料经济性相关的海上天然气储存和碳捕获使用和储存（CCUS）计划。地下储氢（UHS）意味着循环注入/消耗活动，以应对与能源需求相关的季节性波动。为了使循环成功，需要一种缓冲气体来保持储层的压力，而二氧化碳（CO2）是一种很有前途的环保替代品。在大多数储存项目中，通过将地震振幅的变化与流体含量联系起来，对储层流体进行地震监测。然而，如果在CO2缓冲层中注入H2，有几个因素会模糊H2的地震可见性：H2和CO2具有相似的声学性质，它们在注入/提取周期内沉淀的时间很短，通常会将岩石吸收成块，降低流体的有效流动性。在CHORUS中，我们建议通过测试粘度对比是地震H2可探测性的关键这一假设来解决这些问题。我们建议利用我们目前在色散波传播方面的专业知识分三个阶段检验这一假设。首先，我们将对储层岩石的弹性特性进行超声实验室测量，这些岩石中饱和的流体有望在UHS应用中发现。其次，利用CCUS建立的现有岩石物理模型，计算不同饱和度条件下储层岩石的地震速度、衰减和频散，包括盖层密封下饱和h2 -水和co2 -水的储层岩石，并利用实验室测量对这些模型进行校准。第三，我们将通过计算与垂直地震剖面时移实验相对应的合成地震数据来确定这些发现如何扩大规模。利用该合成数据集，我们将进行敏感性分析，以了解H2的地震可探测性极限。通过提高H2- co2界面的地震分辨率，该方案的结果有可能用于降低注入过程的风险，从而提高我们量化H2的能力。它们可以通过确定泄漏风险的代理来为决策者提供信息，并促进工业季节性UHS的注射和监测策略的规划。该方法还可以通过结合压裂对合成地震特征的地质力学影响来进一步评估盖层完整性，这是我们打算在进一步研究中探索的方向。我们建议以两份（六个月）报告的形式传播我们的结果，一份在主要学术期刊上的合作科学出版物，一份合作会议出版物以及岩石物理实验和合成地震实验的公开数据。利用该项目作为概念验证的跳板，我们打算通过NERC推动前沿资助提案寻求与英国的长期合作来巩固其发现。这一建议将包括基础研究、裂缝顶封/储层的详细各向异性建模和地震数据。此外，我们的理论进展可以通过补充岩石物理知识，为NOC （NERC MOET）和UoE （EPSRC HyStorPore）中正在进行的与UHS相关的研究增加价值。

The UK is poised to embrace net zero carbon emission technologies to meet its Paris agreement targets, including offshore gas storage associated with the hydrogen (H2) fuel economy and Carbon Capture Usage and Storage (CCUS) schemes. Underground H2 storage (UHS) implies cyclic injection/depletion activities to deal with seasonal fluctuations associated with energy demands. For the cycle to be successful, a cushion gas is needed to keep the reservoir pressurised, with carbon dioxide (CO2) being a promising environmentally friendly alternative. In most storage projects, reservoir fluids are seismically monitored by associating the variation of seismic amplitude with fluid content. However, if H2 is injected in CO2-cushioned reservoir, several factors obscure the H2 seismic visibility: both H2 and CO2 have similar acoustic properties, and they have short timescales to settle within an injection/extraction cycle, often imbibing the rock in patches and lowering effective fluid mobility. In CHORUS we propose to address these issues by testing the hypothesis that a viscosity contrast is the key to seismic H2 detectability. We propose to test this hypothesis in three stages using our current expertise with dispersive wave propagation. First, we will perform ultrasonic laboratory measurements of elastic properties of reservoir rocks saturated with fluids expected to be found in UHS applications. Second, we will apply existing rock physics models established for CCUS to calculate the seismic velocities, attenuation and dispersion of reservoir rocks under different saturation conditions involving reservoir rocks saturated with H2-water and CO2-water below a caprock seal and calibrate these models using laboratory measurements. Third, we will identify how these finds scale up by calculating synthetic seismic data corresponding to a vertical seismic profile time-lapse experiment. Using this synthetic dataset, we will conduct a sensitivity analysis in order to understand the limits of seismic detectability of H2. Outcomes of this proposal have the potential to be used to de-risk the injection process by enhancing our ability to quantify H2 through better seismic resolution of the H2-CO2 interface. They can be used to inform policy-makers by identifying proxies for leakage risk and facilitate the planning of injection and monitoring strategies for industrial seasonal UHS. The methodology can be further used to asses caprock integrity by incorporating geomechanical effects from fracturing on the synthetic seismic signatures, a direction that we intend to explore in further research. We propose to disseminate our results in the form of two (six monthly) reports, a collaborative scientific publication in a lead academic journal, a collaborative conference publication and openly accessible data from the rock physics experiment and the synthetic seismic experiment. Using this project as springboard proof-of-concept, we intend to consolidate its finds by pursuing a long-term UK collaboration through a NERC Pushing Frontiers funding proposal. Such a proposal would incorporate fundamental research, as well as detailed anisotropic modelling of fractured top-seal/reservoir and seismic data. In addition, our theoretical advancements can add value to ongoing studies associated with UHS, both in NOC (NERC MOET), and UoE (EPSRC HyStorPore) by complementing them with rock physical knowledge.