Title: Dynamics of a compressible gas injected into a confined porous layer Show Chinese title

Title: 可压缩气体注入受限多孔层中的动力学

Abstract: Underground gas storage is a critical technology in global efforts to mitigate climate change. In particular, hydrogen storage offers a promising solution for integrating renewable energy into the power grid. When injected into the subsurface, hydrogen's low viscosity compared to the resident brine causes a bubble of hydrogen trapped beneath caprock to spread rapidly into an aquifer through release of a thin gas layer above the brine, complicating recovery. In long aquifers, the large viscous pressure drop between source and outlet induces significant pressure variations, potentially leading 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 gas/liquid interface height, focusing on the limit of long domains, weak gas compressibility and low gas/liquid viscosity ratio. Simulations 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 viscosity ratio, and compressive effects are transient, we show how 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 coupling allows compressibility to reduce spreading rates and 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应对气候变化努力中的关键技术。 特别是，氢气储存为将可再生能源整合到电网中提供了一个有前景的解决方案。 当注入地下时，与原有的盐水相比，氢气的低粘度导致在盖岩下方被截留的氢气泡通过盐水上方释放的薄气体层迅速扩散到含水层中，这使得回收变得复杂。 在长含水层中，源和出口之间的大粘性压力降会引起显著的压力变化，可能导致注入气体的密度发生重大变化。 为了研究气体可压缩性在扩散动力学中的作用，我们使用长波理论推导出气体压力和气/液界面高度的耦合非线性演化方程，重点研究长域、弱气体可压缩性和低气体/液体粘度比的极限情况。 模拟结果通过参数区域的全面渐近分析得到补充。 与近不可压缩极限不同，在该极限下气体扩散速率由源强度和粘度比决定，而压缩效应是瞬时的，我们展示了主气体气泡的压缩如何产生与在液体上扩散的薄气体层中的压力变化相耦合的动态压力变化，其中压缩效应在整个层中持续影响。 这种耦合使得可压缩性能够降低扩散速率和气体压力。 我们通过一组低阶模型来描述这种行为，这些模型揭示了主导标度，突出了可压缩性在调节气体层演变中的作用。