Safe offshore Carbon Capture Utilization and Storage (CCUS) includes monitoring of the subseafloor, to identify and assess potential CO₂ leaks from the geological reservoir through seal bypass structures. We simulated CO₂-leaking through shallow marine sediments of the North Sea, using two gravity core samples from ∼1 and ∼2.1 m below seafloor. Both samples were subjected to brine−CO₂ flow-through, with continuous monitoring of their transport, elastic and mechanical properties, using electrical resistivity, permeability, P-wave velocity and attenuation, and axial strains. We used the collected geophysical data to calibrate a resistivity-saturation model based on Archie’s law extended for clay content, and a rock physics for the elastic properties. The P-wave attributes detected the presence of CO₂ in the sediment, but failed in providing accurate estimates of the CO₂ saturation. Our results estimate porosities of 0.44 and 0.54, a background permeability of ∼10⁻¹⁵ and ∼10^-17 m², and maximum CO₂ saturation of 18 % and 10 % (±5 %), for the sandier (shallower) and muddier (deeper) sample, respectively. The finer-grained sample likely suffered some degree of gas-induced fracturing, exhibiting an effective CO₂ permeability increase sharper than the coarser-grained sample. Our core-scale multidisciplinary experiment contributes to improve the general interpretation of shallow sub-seafloor gas distribution and migration patterns.

安全的海上碳捕集利用和封存（CCUS）包括对海底的监视，以识别和评估通过密封旁路结构从地质储层中潜在的CO ₂泄漏。我们使用来自海底以下〜1和〜2.1 m的两个重力岩心样本模拟了北海浅海沉积物中的CO ₂泄漏。两个样品都经受盐水-CO _2的作用通过电阻率，磁导率，P波速度和衰减以及轴向应变连续监测其传输，弹性和机械性能。我们使用收集的地球物理数据，根据对粘土含量进行扩展的阿奇定律和针对岩石弹性特性的岩石物理学，校准了电阻率-饱和度模型。P波属性检测到沉积物中存在CO ₂，但未能提供准确的CO ₂饱和度估算值。我们的结果估计孔隙度为0.44和0.54，背景渗透率约为10 ^-15和约10 ^-17  m ²，并且最大CO ₂较沙性（较浅）和泥状（较深）样品的饱和度分别为18％和10％（±5％）。较细颗粒的样品可能遭受了一定程度的气体诱导压裂，与较粗颗粒的样品相比，有效CO ₂渗透率的增加更为明显。我们的核心规模多学科实验有助于改善对浅海底层海底天然气分布和运移模式的一般解释。