目前，国际地缘政治局势复杂多变，能源供应链面临诸多不确定性。储气库作为国家能源储备体系的重要组成部分，可有效地缓冲国际天然气市场价格波动与供应中断风险，保障民生和工业生产等领域稳定用气，成为守护国家能源安全的坚实屏障。对于储气库多组分、多周期注采的高效安全运行，准确掌握储气库中工作气与垫层气的混合气扩散流动规律至关重要。然而，现有的气体扩散实验多聚焦于页岩、煤和致密岩石，对碳酸盐岩中多组分气体扩散规律认识尚不清晰。该研究选用卧龙河气田石炭系黄龙组上统的碳酸盐岩岩样，通过核磁共振和高压压汞实验测定碳酸盐岩孔喉半径分布特征，开展了CH₄与CO₂、N₂、O₂多组分体系的扩散实验，并通过拟合结果对比分析优选了适用于多尺度碳酸盐岩储层的气体扩散系数数学模型。研究表明：碳酸盐岩岩样具有明显的多尺度孔隙分布特征。在相同温度和压力下，岩石孔隙度和渗透率越大，各组分气体的扩散系数越大，CH₄与CO₂的二元扩散系数高于N₂与CO₂的二元扩散系数。在多组分体系扩散中，O₂扩散系数最大，CH₄扩散系数次之，而N₂与CO₂扩散系数最小。O₂的存在影响了CH₄与N₂扩散系数对CO₂和N₂体积分数变化的响应。通过结合实验数据优选的气体扩散系数数学模型可推广应用于不同温度和压力条件下的扩散系数预测。研究成果可为储气库运行规律准确预测和运行制度合理设计提供实验和计算方法。

Currently, the international geopolitical landscape is complex and volatile, with energy supply chains facing significant uncertainties. Gas storage, as a crucial component of the national energy reserve system, can effectively mitigate risks from fluctuations in international natural gas market prices and supply disruptions, ensuring stable gas supply for residential and industrial use, thereby serving as a robust safeguard for national energy security. For the safe and efficient operation of gas storage under multi-component, multi-cycle injection, and production conditions, accurately understanding the diffusion and flow patterns of mixed gases—working gas and cushion gas—in gas storage is essential. However, experimental studies on gas diffusion mainly focus on shale, coal, and tight formations, leaving the diffusion patterns of multi-component gases in carbonate reservoirs poorly understood. In this study, carbonate rock samples from the Upper Carboniferous Huanglong Formation (upper member) of the Wolonghe gasfield were examined, and the distribution of pore-throat radius were characterized using nuclear magnetic resonance and high-pressure mercury intrusion experiments. Diffusion experiments were conducted on gas mixtures containing CH₄ with CO₂, N₂, and O₂. Through comparative analysis of fitting results, the optimal mathematical model for gas diffusion coefficients applicable to multiscale carbonate reservoirs was selected. The results showed that the carbonate rock samples exhibited pronounced distribution characteristics of multi-scale pore structure. Under identical temperature and pressure conditions, higher porosity and permeability led to larger diffusion coefficients for all gas components. Moreover, the binary diffusion coefficient of the CH₄-CO₂ pair exceeded that of the N₂-CO₂ pair. In a multi-component system, O₂ exhibited the largest diffusion coefficient, followed by CH₄, while N₂ and CO₂ had the smallest diffusion coefficients. The presence of O₂ affected how the diffusion coefficients of CH₄ and N₂ responded to changes in the volumetric fractions of CO₂ and N₂. The mathematical model optimized using experimental data can be extended to predict diffusion coefficients under different temperature and pressure conditions. These findings provide experimental and computational methods for accurately predicting the patterns of gas storage operations and designing rational operational strategies.