Humic substances and salts are widely distributed in marine sediments, a phenomenon that undoubtedly increases the complexity of recovering methane from hydrate. In this work, kinetic experiments were carried out to determine the role of fulvic acid (FA) on methane hydrate formation and decomposition in marine sediments. We used the mixed clay-rich silty with pore water, containing 3.0 wt% NaCl, to simulate the sediments, with experimental pressure (12.7–14.6 MPa) and temperature (8.6–16.2 °C) conditions adopted from the hydrate reservoir of Shenhu area, South China Sea (SHCS). Results revealed that FA has favorable/unfavorable effects on methane hydrate formation in the sediments, in a concentration-dependent manner. FA solutions, at concentrations of 6.0 and 10.0 wt%, inhibited the formation of methane hydrate, because the high-water holding capacity itself could reduce water activity. Conversely, 2.0 wt% FA solution accelerated methane hydrate formation by arranging surrounding water molecules with H-bonds. Interestingly, it was found that the addition of FA could significantly weaken NaCl's inhibitory effect on methane hydrate formation, while water conversion ratios increased ∼2/3-fold relative to NaCl without FA solution containing systems. These results suggested that presence of FA in marine sediments promoted hydrate reformation during reservoir production. Besides, we found that there is a synergistic effect between FA and NaCl in the process of methane decomposition.

腐殖质和盐类广泛分布于海洋沉积物中，这一现象无疑增加了从水合物中回收甲烷的复杂性。在这项工作中，进行了动力学实验以确定富里酸 (FA) 对海洋沉积物中甲烷水合物形成和分解的作用。我们使用含有 3.0 wt% NaCl 的富含粘土的粉质混合孔隙水来模拟沉积物，采用来自神湖地区水合物储层的实验压力（12.7-14.6 MPa）和温度（8.6-16.2 ℃）条件。 , 南海 (SHCS)。结果表明，FA 对沉积物中甲烷水合物的形成具有有利/不利影响，且呈浓度依赖性。浓度为 6.0 和 10.0 wt% 的 FA 溶液抑制甲烷水合物的形成，因为高保水能力本身会降低水分活度。相反，2.0 wt% 的 FA 溶液通过用氢键排列周围的水分子来加速甲烷水合物的形成。有趣的是，发现添加 FA 可以显着削弱 NaCl 对甲烷水合物形成的抑制作用，而与不含 FA 溶液系统的 NaCl 相比，水的转化率增加了 2/3 倍。这些结果表明，海洋沉积物中 FA 的存在促进了储层生产过程中的水合物改造。此外，我们发现FA和NaCl在甲烷分解过程中存在协同作用。有趣的是，发现添加 FA 可以显着削弱 NaCl 对甲烷水合物形成的抑制作用，而与不含 FA 溶液系统的 NaCl 相比，水的转化率增加了 2/3 倍。这些结果表明，海洋沉积物中 FA 的存在促进了储层生产过程中的水合物改造。此外，我们发现FA和NaCl在甲烷分解过程中存在协同作用。有趣的是，发现添加 FA 可以显着削弱 NaCl 对甲烷水合物形成的抑制作用，而与不含 FA 溶液系统的 NaCl 相比，水的转化率增加了 2/3 倍。这些结果表明，海洋沉积物中 FA 的存在促进了储层生产过程中的水合物改造。此外，我们发现FA和NaCl在甲烷分解过程中存在协同作用。