地下多孔储层氢气存储是在氢能大规模应用的情境下大规模、长周期储氢的关键技术。储气库的致密盖层中存在大量纳米尺度孔隙，深入认识纳米孔隙中吸附气体的热力学、动力学性质并开发高效、准确表征方法对于储气库泄漏风险的评估十分关键。核磁共振弛豫是实验室分析与地球物理测井中常用的表征技术，开发基于核磁弛豫的纳米孔隙内气体吸附性质表征方法对于储气库的勘探与评价将具有重要意义。另一方面，氢气注入地层后可能引起氢营养微生物代谢，改变地层水成分，进而引发矿物溶解，改变储层渗流特性。明晰储层多孔介质中化学反应与流动传质的耦合作用规律对地层流体演化运移的准确预测与调控至关重要。本文针对纳米多孔介质吸附气体核磁弛豫机理不清、缺少基于核磁弛豫的吸附性质表征手段、砂岩储层矿物非均质多孔介质中反应与流动耦合规律不清等问题，通过理论分析、数值模拟与实验测量等手段开展了相应研究。首先，通过理论分析建立了联系孔内流体表面弛豫率与分子运动的关系式，发展了基于分子模拟的核磁弛豫率计算方法，实现了孔内吸附气体各类核磁弛豫率的模拟计算。揭示了吸附气体核磁弛豫的分子尺度机理，解释了纳米孔隙内吸附气体弛豫时间长于体相这一有悖于传统受限流体核磁弛豫理论的现象，并提出了联系弛豫率与孔隙结构、气体吸附量及自扩散系数的定量理论模型。其次，通过标准纳米多孔材料吸附高压氢气、甲烷的核磁测量与理论分析证实了气体在吸附态与自由态之间的交换将影响多组分反演获得的弛豫谱，为此提出了基于Bloch-Torrey方程的气体吸附体系核磁弛豫率反演新方法。结合所提出的理论模型，开发了基于核磁弛豫的纳米孔隙内气体吸附性质表征新方法，与传统表征方法结果对比验证了准确性，并应用于了3类UiO-66衍生材料的表征。测量了典型盖层岩石页岩中吸附氢气的核磁弛豫过程，获得了页岩中的氢气吸附量。最后，开发了矿物分布、孔隙结构与真实砂岩类似的矿物非均质多孔介质微模型，通过孔隙尺度矿物溶解实验与流场数值模拟获得了不同可溶矿物比例及不同贝克莱数、达姆科勒数下的溶蚀结构相图，阐明了渗透率、反应比表面积、单位反应表面积溶解速率等关键宏观参数随孔隙率的演变规律及其孔隙尺度机理，为地层中化学反应影响下流体演化运移的预测模型提供了理论支撑。
The underground hydrogen storage in porous reservoir is a key technology for large-scale and long-term hydrogen storage in the context of large-scale application of hydrogen energy. There are a large number of nano-scale pores in the caprock of the gas storage reservoir. It is crucial to deeply understand the thermodynamic and kinetic properties of adsorbed gas in nano-pores and develop efficient and accurate characterization methods for evaluating the leakage risk of the gas storage reservoir. Nuclear magnetic resonance relaxation is a commonly used characterization technology in laboratory analysis and geophysical logging. The development of a characterization method for gas adsorption properties in nano-pores based on nuclear magnetic resonance (NMR) relaxation will be of great significance for the exploration and evaluation of gas storage reservoirs. On the other hand, hydrogen injection into the formation may cause the metabolism of hydrogenotrophic microorganisms wich will change the composition of formation water, and further trigger mineral dissolution. In order to achieve accurate prediction and regulation of the evolution and migration of formation fluids, it is necessary to clarify the coupling effects of chemical reactions, fluid flow, and mass transfer in the porous media of the reservoir.To address issues such as the unclear mechanism of NMR relaxation of adsorbed gas in nanoporous media, the lack of characterization methods for adsorption properties based on NMR relaxation, and the unclear coupling laws between reactions and fluid flow in heterogeneous porous media of sandstone reservoirs, this dissertation conducts corresponding research through theoretical analysis, numerical simulation, and experimental measurement.First, a relationship between the surface relaxation rate of fluid in pores and molecular motion is established through theoretical analysis. A calculation method for NMR relaxation rates based on molecular simulation is developed, enabling the simulation and calculation of various NMR relaxation rates of adsorbed gas in pores. This reveals the molecular-scale mechanism of NMR relaxation of adsorbed gas and explains the phenomenon that the relaxation time of adsorbed gas in nanopores is longer than that in bulk phases which contradicts the traditional NMR relaxation theory for confined fluids. Then a quantitative theoretical model is proposed that links relaxation rates with pore structure, gas adsorption amount, and self-diffusion coefficient.Secondly, through NMR measurements and theoretical analysis of standard nanoporous materials adsorbing high-pressure hydrogen and methane, it is confirmed that the exchange between the adsorbed state and the free state of gas will affect the relaxation spectrum obtained from multi-component inversion. Therefore, a new inversion method for NMR relaxation rate of gas adsorption systems based on the Bloch-Torrey equation is proposed. Combining with theoretical models, a new method for characterizing gas adsorption properties in nanopores based on NMR relaxation is developed. The accuracy is verified by comparing with traditional characterization methods, then it is applied to the characterization of three types of UiO-66 derivative materials. The NMR relaxation process of adsorbed hydrogen in typical caprock shale is measured, and the adsorption capacity of hydrogen in shale is obtained.Finally, a micro-model of mineral heterogeneous porous media with similar mineral distribution, pore structure with real sandstone is developed. Through pore-scale mineral dissolution experiments and numerical simulation of flow fields, dissolution structure phase diagrams under different soluble mineral ratios, Peclet numbers, and Damk?hler numbers are obtained. The evolution of key macroscopic parameters such as permeability, reactive specific surface area, and dissolution rate per unit reactive surface area with porosity and their pore-scale mechanisms are elucidated, providing theoretical support for prediction models of fluid evolution and migration under the influence of chemical reactions in the formation.
