含杂质CO2管道输送水合物形成规律研究

Study on the formation law of hydrate in pipeline containing-impurity CO2

关键词:  CO₂水合物  黏度  堵塞  压降

Key words:  CO₂ hydrate  viscosity  blockage  pressure drop

摘要:

在延长油田产生的CO₂气体输送过程中,管线会发生水合物冰堵,影响气体输送流量,为了探究CO₂水合物在管道输送过程中的形成规律,利用PVTSIM软件生成了CO₂水合物的相平衡曲线,并通过OLGA软件对水平管和弯管输送的水合物形成规律进行了模拟分析。结果 表明:在低温高压条件下,水平管和弯管输送过程中均会有水合物形成,其生成过程是一种类似于盐类的结晶过程,通常包括成核和生长两个阶段,然后依靠流体颗粒之间的黏附力致使水合物聚集,与直管段相比,弯管段更容易产生水合物；水合物生成速率均由小到大,然后快速进入稳定阶段,最后趋于0。现场管线的水合物也多发生在弯管处,从而进一步验证了CO₂水合物的形成规律。因此,在管道输送过程中应避免高压出口和低温入口条件,保证管道安全运营。 

Abstract:

The hydrate ice plugging which affects the gas transportation flow often occur in the pipeline during the CO₂ gas transportation at Yanchang oilfield. In order to explore the formation law of CO₂ hydrate, the phase equilibrium curve of CO₂ hydrate is generated by PVTSIM software. The hydrate formation law in horizontal section and bend section of pipe is simulated by OLGA software. The results show that at low temperature and high pressure, hydrate formation occurs in horizontal section and bend section of pipe. The formation process is a kind of salt-like crystallization, which usually includes two stages of nucleation and growth, and then relies on the adhesion force between fluid particles to cause hydrate aggregation. Compared with the straight section of pipe, it is found that the bend section of pipe is easier to produce hydrate. The hydrate formation rate is from low to high,then quickly enters the stable stage, and finally tends to 0. And the hydrate also occuring at the bend section of pipe in field further verifies the formation law of CO₂ hydrate in this paper. Therefore, in the process of pipeline transportation, the conditions of high pressure outlet and low temperature inlet are avoided to ensure the safe operation of pipeline.