基于Multiflash的天然气水合物相平衡影响因素及规律

Study on influence factors and rules of gas hydrate phase equilibrium based on multiflash software

通过Multiflash软件对影响水合物相平衡条件的气体组分、抑制剂、盐类、温度、压力及含水量进行了数值模拟计算,探讨这些因素对天然气水合物相平衡的影响规律及作用机制。结果表明:乙烷、丙烷、H2S对水合物生成有促进作用,丙烷效果好于乙烷,CO2、N2对水合物相平衡影响不大;甲醇、乙醇及其混合物对水合物生成起抑制作用,甲醇抑制效果要优于乙醇,甲醇和乙醇的混合物抑制效果处于两者之间。含量的累积不会影响甲醇抑制效果,乙醇单位含量抑制效果随着总含量增加而减弱。NaCl、MgCl2对水合物起抑制作用,且MgCl2抑制效果好于NaCl。NaCl、MgCl2单位含量抑制效果随含量增加而增强。压力较低时,压力变化对水合物平衡温度影响较大;温度较高时,温度变化对水合物平衡压力影响较大;自由水含量与水合物生成量呈正比例关系,组分对水合物临界含水量影响有限。天然气水合物相平衡条件受多种因素影响,在勘探、钻探及流动保障过程中要考虑这些影响规律,提高水合物勘探、生产或者防治效率。

Numerical simulation by Multiflash software has been made to unravel the factors that affect the hydrate phase equilibrium conditions,such as gas components,inhibitors,salts,temperatures,pressures and water content,and the effects of these factors on the phase equilibrium of natural gas hydrate and their mechanisms have been discussed.The results showed that ethane,propane and H2S promoted hydrate formation,propane was better than ethane,and CO2 and N2 had little effect on hydrate phase equilibrium.The inhibition effect of methanol,ethanol and their mixture on the formation of hydrate was better than that of ethanol.The accumulation of methane content did not affect its inhibitory effect,but the unit content inhibition effect of ethanol decreased with the increase of its content.NaCl and MgCl2 could inhibit the formation of hydrate,and the inhibitory effect of MgCl2 was significantly better than that of NaCl.The unit content inhibiting effect of NaCl and MgCl2 increased with the increase of content.When pressure was low,the pressure variation had a great influence on the hydrate equilibrium temperature.When temperature was high,the temperature change had a greater influence on the hydrate equilibrium pressure.There was a positive proportional relation between free water content and hydrate content in the system.It was showed that the components had little influence on the water content required for hydrate formation.Gas hydrate phase equilibrium conditions were affected by variety of factors,which should be considered in the process of exploration,drilling and flow assurance so as to improve hydrate production or control efficiency.