三醋酸甘油酯抑制水合物生成分子动力学模拟及实验研究

Molecular Dynamics Simulation and Experimental Study on the Inhibition of Hydrate Formation with Glycerol Triacetate

为防止海洋深水钻井过程中在管线中生成水合物堵塞管线和海底防喷器,需要应用高效的水合物抑制剂。利用NPT系综分子动力学模拟研究温度4℃、压力20 MPa的条件下,三醋酸甘油酯对sⅠ型水合物的分解过程,以及三醋酸甘油酯和NaCl的协同作用,并进行实验验证。分析表明,三醋酸甘油酯分子能够与水分子形成氢键,从而破坏水合物笼型结构;加入NaCl能降低水活度,从而破坏水合物稳定存在的平衡条件;水合物的分解主要在前50 ps内,三醋酸甘油酯与NaCl共同作用的水合物分子的扩散系数大于单独使用三醋酸甘油酯。在4℃、20 MPa实验条件下,0.5%三醋酸甘油酯的反应平衡压力为18.75 MPa;0.5%三醋酸甘油酯+10%NaCl反应平衡压力为18.91 MPa,验证了三醋酸甘油酯的水合物抑制性及三醋酸甘油酯与NaCl的协同效应。研究结果对研发新型超深水钻井液水合物抑制剂及配方有参考意义。

High efficiency hydrate inhibitors are generally used in offshore deep water drilling to prevent the formation of hydrate which is able to plug pipelines and subsea blowout preventers(BOPs).In laboratory experiment,the decomposition of sI hydrate by glycerol triacetate and the synergy between glycerol triacetate and NaCl were studied at 4℃and 20 MPa,using NPT ensemble molecular dynamics.The experimental results showed that the hydrogen bonds between glycerol triacetate and water destroyed the cage structure of the hydrate molecules.NaCl is able to reduce the activity of water,thereby destroying the equilibrium conditions under which the hydrate is stabilized.The decomposition of hydrate mainly takes place in the first 50 ps;the diffusion coefficient of the hydrate molecules under the co-action of glycerol triacetate is greater than the diffusion coefficient of the hydrate molecules under the action of glycerol triacetate alone.At 4℃and 20 MPa,the reaction equilibrium pressure of 0.5%glycerol triacetate is 18.75 MPa,and that of 0.5%glycerol triacetate+10%NaCl is 18.91 MPa,verifying the hydrate inhibitive capacity of glycerol triacetate and the synergy between glycerol triacetate and NaCl.The study findings can be used in developing new hydrate inhibitors for ultra-deep water drilling and in formulating hydrate inhibitors.