Evaluation of fault leakage rates in the context of subsurface hydrogen and carbon storage

在地下临时储存氢气或永久储存二氧化碳需要深刻理解相关的泄漏风险，以及仍有待量化的环境，政治和经济风险。沿着威尔斯或断层泄漏的风险最高。后者（图1）可能已经具有流体动力学传导性，或者传导性可能由CO2或H2注入引起的流体压力增加触发。流体压力的增加，从而有效应力的降低，取决于注入井的断层附近。在已知的断层附近钻注井是相当不鼓励的，而它仍然是未知的，如果断层可以作为泄漏途径超过工程时间尺度上的顺序<10，000 years.在这种情况下，我们将调查多相流效应的影响，从地质油藏用于流体存储，特别是CCS和氢的故障泄漏。这项研究将基于瑞士光源的多尺度4D X射线成像获得的最新数据。这个博士项目将提供新的和详细的见解多相流体动力学粗糙裂缝。使用同步加速器实验的新数据将支持更准确地预测地下储层的潜在流体泄漏率。迫切需要这些来提高我们对长期地下流体储存的信心。本研究主要分为以下几个方面：1.基于4D流动数据，深入了解粗糙裂缝中的多相流。将针对位移分析数据，以获得在给定有效应力下的相对渗透率和毛细管压力曲线，但具有不同的表面粗糙度、孔径异质性和流速（毛细管数）。在裂缝和裂缝网络的物理模型中以达西尺度表示裂缝流动现象。这将支持盖层泄漏风险评估，通过将裂缝网络数据（来自PI/co-Is以前的研究）和本研究的放大流体驱替模型结合在一起，提高我们确定泄漏率的信心。

Temporary storage of hydrogen or permanent storage of carbon dioxide in the subsurface requires a profound understanding of associated risks for leakage, bearing environmental, political, and economic risks that are still to be quantified. Risks are highest for leakage along wells or faults. The latter (Fig. 1) might already be hydro-dynamically conductive, or conductivity might be triggered by an increase in fluid pressures due to CO2 or H2 injection. Fluid pressure increase, and thus effective stress decrease, depends on the vicinity of the faults to the injection well. Drilling an injection well near a known fault is rather discouraged, while it remains unknown if faults can act as leakage pathways over engineered time scales on the order of < 10,000 years.In this context, we will investigate the impact of multiphase flow effects on fault leakage from geological reservoirs used for fluid storage, focusing specifically on CCS and hydrogen. This research will ground on recent data that has been obtained from multiscale 4D X-ray imaging at the Swiss Light Source. This PhD project will provide new and detailed insights into the multiphase fluid dynamics in rough fractures. Using novel data from synchrotron experiments will support more accurate predictions of the potential fluid leak rates from subsurface reservoirs. These are urgently needed to improve our confidence in subsurface fluid storage over long periods of time. This research can be divided into the following objectives:1. Develop a robust understanding of multiphase flow in rough fractures, based on 4D flow data. The data will be analysed towards displacement to obtain relative permeability and capillary pressure curves at a given effective stress but with varying surface roughness, aperture heterogeneity, and flow rates (capillary numbers).2. Represent fracture flow phenomena at the Darcy scale in physical models for fractures and fracture networks. This will support caprock leakage risk assessments by improving our confidence in the determination of leak rates by bringing together fracture network data (from previous research by the PI/co-Is) and upscaled fluid displacement models from this research.