Title: Dynamic injection of a compressible gas into a confined porous layer Show Chinese title

Title: 可压缩气体动态注入到一个受限的多孔层中

Abstract: Subsurface gas storage is a critical technology in global efforts to mitigate climate change. In particular, underground hydrogen storage offers a promising solution for integrating large-scale renewable energy into the power grid. When injected into the subsurface, hydrogen's low viscosity compared to the resident brine causes it to spread rapidly, forming a thin gas layer above the brine, complicating recovery. In long aquifers, the large viscous pressure drop between the source and the outlet induces significant pressure variations, which may lead to substantial density changes in the injected gas. To examine the role of gas compressibility in the spreading dynamics, we use long-wave theory to derive coupled nonlinear evolution equations for the gas pressure and liquid/gas interface height, focusing on the limit of long domains, weak gas compressibility and low liquid/gas mobility ratio. Simulations using these equations are supplemented with a comprehensive asymptotic analysis of parameter regimes. Unlike the near-incompressible limit, in which gas spreading rates are dictated by the source strength and mobility ratio, and any compressive effects are transient, we show how, in general, compression of the main gas bubble can generate dynamic pressure changes that are coupled to those in the thin gas layer that spreads over the liquid, with compressive effects having a sustained influence along the layer. This allows compressibility to reduce spreading rates and lower gas pressures. We characterise this behaviour via a set of low-order models that reveal dominant scalings, highlighting the role of compressibility in mediating the evolution of the gas layer. Show Chinese abstract

Abstract: 地下气体储存是全球努力减缓气候变化的关键技术。特别是地下氢气储存为大规模可再生能源并入电网提供了有前景的解决方案。当注入地下时，相比于驻留的盐水，氢气较低的黏度使其迅速扩散，形成一层薄薄的气体层位于盐水上部，这使得回收过程变得复杂。在长水层中，源点与出口之间较大的黏性压力降会导致显著的压力变化，这些变化可能引起注入气体密度的大幅变化。为了研究气体压缩性在扩散动力学中的作用，我们使用长波理论推导了描述气体压力和液气界面高度的耦合非线性演化方程，重点在于长域、弱气体压缩性和低液气流动性比的限制条件下。使用这些方程进行的模拟得到了参数范围的全面渐近分析补充。与近不可压缩极限不同，在该极限下，气体扩散速率由源强和流动性比决定，并且任何压缩效应都是瞬态的，我们展示了如何一般情况下，主要气体泡的压缩可以生成动态压力变化，这些变化与覆盖在液体上的薄气体层的扩散耦合在一起，压缩效应沿层持续影响。这允许压缩性降低扩散速率并减少气体压力。我们通过一组低阶模型来表征这种行为，揭示主导尺度，突出压缩性在调节气体层演化中的作用。