Abstract Pipe blockage due to gas hydrate formation is a main concern in the oil and gas industry due to the revenue losses caused by either production impairments or interruptions, and to the high costs associated to the elimination of such blockages. Assuming a hydrate formation rate in the gas-water interface based on the system subcooling, the present work models the transition from two-phase liquid-gas to three-phase solid-liquid-gas flows when hydrates form. The multiphase flow is assumed to be within the slug flow pattern region, as this is the prevailing flow regime in offshore production scenarios. The model couples mass, momentum and energy balances for the slug flow unit cell. The hydrate phase is assumed as homogeneously dispersed in the water. The gas and water consumption rates due to hydrate formation are modeled as source terms in the mass balance equations. The exothermic characteristic of the hydrate formation is taken into account in the energy conservation equation. The model provides analytic expressions for temperature and pressure distributions along the pipeline. However, the unit cell geometry is solved by numerical integration and the model closure is achieved only when empirical correlations for the slug frequency, the unit cell translational velocity and the slug aeration are used. The results from the numerical simulations are presented for the same input parameters for cases with and without hydrate formation. The discussion focuses on the influence of hydrate formation in the slug flow hydrodynamics and heat transfer. The main mechanisms affecting the mixture temperature and pressure distributions, the mixture heat transfer coefficient, the superficial velocities of the phases, the liquid loading, the slug flow frequency and the unit cell geometry are presented.

中文翻译：

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水合物分散体形成与传热传质耦合的三相固-液-气段塞流机理模型

摘要 由于天然气水合物形成导致的管道堵塞是石油和天然气行业的一个主要问题，因为生产受损或中断造成收入损失，以及与消除此类堵塞相关的高成本。假设基于系统过冷的气-水界面中的水合物形成速率，本工作模拟了当水合物形成时从两相液-气流向三相固-液-气流的转变。假设多相流处于段塞流模式区域内，因为这是海上生产场景中的主要流态。该模型耦合了段塞流晶胞的质量、动量和能量平衡。假设水合物相均匀地分散在水中。由于水合物形成导致的气体和水消耗率被建模为质量平衡方程中的源项。在能量守恒方程中考虑了水合物形成的放热特性。该模型提供了管道沿线温度和压力分布的解析表达式。然而，晶胞几何是通过数值积分求解的，并且只有在使用段塞频率、单位胞平移速度和段塞曝气的经验相关性时才能实现模型闭合。对于有和没有水合物形成的情况，对于相同的输入参数，给出了数值模拟的结果。讨论的重点是水合物形成对段塞流流体动力学和传热的影响。