Abstract High pressure rheological properties of methane hydrate slurries entail the high-pressure rheometer that can deliver a suitable mixing to form in situ methane hydrate from the multiphase system. However, the hydrate formation was extremely challenging in conventional cup and bob geometry due to its plane surface. In this work, modified Couette geometry has been used in a high pressure rheometer to study in situ formation and dissociation of methane hydrate slurries formed from multiphase water-hexane (C6H14), water-heptane (C7H16) and water-decane (C10H22), with varying water-to-liquid hydrocarbon ratios (50:50, 30:70 v/v). Rheological properties such as viscosity, flow curve measurements, viscoelastic properties have been measured during hydrate formation and dissociation. Transient viscosity measurements are carried out at 10 MPa and 275.15 K at a shear rate of 1000 s−1. It was observed that the viscosity increases significantly during hydrate induction. Viscosity profile has shown bobbing behavior during the course of hydrate formation indicating in situ morphological changes (agglomeration and breakage of hydrate crystals) during hydrate formation. Flow curves indicate strong shear thinning behavior. Viscosity profile of methane hydrate slurries were also observed for each case during the hydrate dissociation using thermal stimulation. The peak in the viscosity has been identified near hydrate equilibrium condition during dissociation. Dynamic viscoelastic properties indicate solid behavior of methane hydrate slurries. The present study provides significant contribution on the rheology of methane hydrate slurries formed from multiphase systems in the context of flow assurance applications.

中文翻译：

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由水-己烷、水-庚烷和水-癸烷多相系统形成的甲烷水合物浆液的高压流变研究

摘要 甲烷水合物浆体的高压流变特性需要高压流变仪，它可以提供适当的混合以从多相系统原位形成甲烷水合物。然而，由于其平面表面，水合物的形成在传统的杯子和鲍勃几何形状中极具挑战性。在这项工作中，改进的 Couette 几何结构已用于高压流变仪，以研究由多相水-己烷 (C6H14)、水-庚烷 (C7H16) 和水-癸烷 (C10H22) 形成的甲烷水合物浆液的原位形成和解离，具有不同的水与液体烃比（50:50、30:70 v/v）。在水合物形成和解离过程中测量了流变特性，例如粘度、流动曲线测量、粘弹性。瞬态粘度测量在 10 MPa 和 275.15 K 下以 1000 s-1 的剪切速率进行。观察到在水合物诱导期间粘度显着增加。粘度曲线在水合物形成过程中显示出波动行为，表明水合物形成过程中的原位形态变化（水合物晶体的团聚和破裂）。流动曲线表明强烈的剪切稀化行为。在使用热刺激的水合物分解过程中，还观察了每种情况下甲烷水合物浆液的粘度分布。在离解过程中，在接近水合物平衡条件时确定了粘度峰值。动态粘弹性能表明甲烷水合物浆液的固体行为。