羧甲基纤维素钠对CH4水合物形成过程的影响

羧甲基纤维素钠（CMC-Na）是水基钻井液中的重要组分，为研究CMC-Na对天然气水合物热力学和动力学的影响，实验测量了质量浓度介于0.5%～1.5%的CMC-Na溶液中甲烷水合物的相平衡条件，以及275.2 K、6 MPa的初始条件下CMC-Na溶液中甲烷水合物的形成过程。研究结果表明，CMC-Na对甲烷水合物的热力学稳定性具有微弱的抑制作用，相同压力下相平衡温度降低了0.1～0.2 K。CMC-Na溶液中形成的甲烷水合物为Ⅰ型，水合物数为5.84～5.90。在CMC-Na溶液中，甲烷水合物形成所需的诱导时间大大缩短，表明CMC-Na对甲烷水合物的形成过程具有促进作用。在CMC-Na溶液中水合物生成所需气体消耗量呈阶段式增长。水合物转化率低于35%的情况下，已经生成的水合物没有对搅拌器叶片形成持续附着进而卡住搅拌器。因此，CMC-Na对甲烷水合物的热力学稳定性具有一定的负面影响，对水合物的形成具有一定的促进作用。另外，CMC-Na能够降低水合物生成过程中搅拌扭矩的波动，对维持搅拌的正常运行具有重要作用。

Effect of Sodium Carboxymethyl Cellulose on the Formation of CH4 Hydrate

Sodium carboxymethyl cellulose (CMC-Na) is an important component of water based drilling fluid. To investigate the influence of CMC-Na on thermodynamic and kinetic performance of methane hydrate formation, the equilibrium conditions of methane hydrate in the presence of CMC-Na and the formation kinetics of methane hydrate at 275.2 K and 6 MPa were measured in this work. The results showed that CMC-Na had a slight inhibitory effect on the thermodynamic stability of methane hydrate. The equilibrium temperature increased by 0.1 - 0.2 K. Methane was found to form sI hydrate in CMC-Na solution and the hydration number ranged from 5.84 to 5.90. In CMC-Na solution, the induction time reduced greatly, suggesting a promotion effect of CMC-Na on hydrate formation. The gas consumption of methane hydrate formation grew in stages. When hydrate conversion rate was below 35%, the formed CH₄ would not adhere continuously or stuck stirrer. Therefore, CMC-Na showed a negative effect on thermodynamic stability and a promotion effect on hydrate formation. In addition, CMC-Na can narrow the fluctuation of the stirring torque during hydrate formation, which was beneficial to maintain the normal operation of agitation.