Seep carbonates tell us where and when CH₄-charged fluids escaped from the subsurface, thus providing qualitative information to reconstruct the activity of petroleum systems. The potential of seep carbonates as quantitative proxies for the amount of CH₄ leaked, however, remains largely unexplored, which limit their applicability as exploration tools. This paper tackles the quantification of the CH₄ flux - seep carbonate relationship by simulating the coupled sedimentary carbon (C) – sulfur (S) cycles in a reaction-transport modeling (RTM) framework. We first establish a theoretical basis demonstrating that the stoichiometry of diagenetic reactions and the ambient pH of pore waters are the main drivers of the rate of change in the saturation state of carbonate minerals (Ω_Cal), while the concentrations of total dissolved inorganic carbon and sulfide are only of secondary importance. It results that anaerobic oxidation of methane (AOM) is the main driver of carbonate precipitation, while organoclastic sulfate reduction (SR) has a minor impact. We further show that SR mostly drives carbonate dissolution, but can also contribute to precipitation when pH is low (<7–7.1). The RTM simulations reveal that an increase in upward fluid flow triggers an intensification of peak AOM rates, associated to a shallowing and thinning of the zone of carbonate precipitation. Such behavior leads to an almost linear relationship between the amount of carbonate precipitated and flux of CH₄ (nCH₄ = 3.3–5.2 * nCaCO₃), until, eventually, full cementation occurs. We thus define a “quantitative domain” at moderate fluid flow and a “threshold domain” at high fluid velocities, where full cementation solely provides a lower bound estimate of the amount of CH₄ leaked. We also show that in contrast to a traditional view of seep carbonate formation mainly controlled by venting activity, sedimentation rate and water depth also play major roles, via their control on residence time and saturation concentration of CH₄, respectively. The interpretation of vertical seep carbonate stacks should thus not solely focus on changes in fluid flow, but also consider changes in sedimentation rate and/or water depth.

渗透碳酸盐告诉我们，充有CH ₄的流体何时何地从地下逸出，从而提供了定性信息来重建石油系统的活动。然而，渗碳碳酸盐作为泄漏CH ₄量的定量代理的潜力仍未得到充分开发，这限制了其作为勘探工具的适用性。本文讨论了CH ₄的量化通过在反应运输模型（RTM）框架中模拟耦合的沉积碳（C）-硫（S）循环，分析通量-碳酸盐渗透率之间的关系。我们首先建立一个理论基础，证明成岩反应的化学计量和孔隙水的环境pH是碳酸盐矿物饱和状态变化率的主要驱动力（_ΩCal），而总溶解的无机碳和硫化物的浓度仅次要。结果表明，甲烷的厌氧氧化（AOM）是碳酸盐沉淀的主要驱动力，而有机碎屑硫酸盐的还原（SR）的影响较小。我们进一步表明，SR主要驱动碳酸盐的溶解，但在pH值低（<7-7.1）时也可能有助于沉淀。RTM模拟显示，向上流动的增加会触发峰值AOM速率的增强，这与碳酸盐沉淀区域的变浅和变薄有关。这种行为导致沉淀的碳酸盐量与CH _4的通量之间几乎呈线性关系（ nCH ₄ = 3.3–5.2 * nCaCO ₃），直到最终发生完全胶结。因此，我们在中等流速下定义了一个“定量域”，在高流速下定义了一个“阈值域”，其中完全胶结仅提供了泄漏的CH ₄量的下限估计。我们还表明，与传统的渗透碳酸盐形成的主要观点相反，渗透碳酸盐的形成主要受放空活动控制，沉降速率和水深也分别通过控制CH _4的停留时间和饱和浓度而起主要作用。因此，对垂直渗透碳酸盐岩烟囱的解释不仅应着眼于流体流量的变化，而且还应考虑沉降速率和/或水深的变化。