抑制剂作用下水合物分解机理的分子模拟

发布时间：2018-08-11 10:10

【摘要】：注剂法是水合物开发的最重要方式之一,同时水合物也是油气安全生产的一大隐患,添加化学抑制剂是有效解决水合物堵塞的措施之一。宏观的实验可以为抑制剂选择提供数据支持,但很难从微观层面反映水合物的分解过程和抑制剂的作用机理。分子模拟可用于抑制剂微观作用机理的研究,并为抑制剂评价提供新方法。采用分子动力学方法,建立水合物-抑制剂溶液体系模型,模拟了265-273K条件下,I型甲烷水合物在无机盐(NaCl、KCl、CaCl_2)和醇类(甲醇、乙二醇)溶液中的分解过程,通过计算模拟体系中各组分间的结构、运动和能量变化等参数,分析了抑制剂种类、浓度和温度压力对水合物分解的影响。而且,研究了水合物晶胞对无机盐离子的承受能力,以及动力学抑制剂分子(PVP、PEO、PVCap)在水合物表面的吸附和对水合物分解的影响,探讨了抑制剂的微观作用机理。模拟结果表明,水合物分解形成的液膜可延缓分解进程,无机盐离子有利于突破液膜结构,缩短分解停滞的时间,分解速率与无机盐浓度呈正比,在分解过程中分解速率均不是恒定的。水合物分解过程中所需吸收的能量不同,其中KCl能量最大,当CaCl_2浓度超过30wt%时,所需吸收能量最低。离子对晶胞的破坏能力不同,Ca~(2+)2K~+2Cl~-2Na~+。在醇类溶液中,形成的液膜结构松散,不能延缓水分子的扩散,溶液浓度在20wt%-30wt%时,水合物分解速率最大。水合物分解过程中分解热先随浓度增加逐渐减小,在30wt%以后又逐渐上升。与温度相比,受限空间体积对分解过程影响不大。动力学抑制剂与水合物表面的相互作用能受浓度和分子量的影响,PVCap对水合物的分解能力最强,抑制剂分子加强了近程(2.5?)水分子结构的有序性。
[Abstract]:The injection method is one of the most important methods for hydrate development, and hydrate is also a hidden danger in the safe production of oil and gas. Adding chemical inhibitors is one of the effective measures to solve hydrate blockage. Macroscopical experiments can provide data support for inhibitor selection, but it is difficult to reflect the decomposition process of hydrate and the mechanism of inhibitor action from the microscopic level. Molecular simulation can be used to study the mechanism of microcosmic action of inhibitors and provide a new method for evaluation of inhibitors. The model of hydrate inhibitor solution system was established by molecular dynamics method. The decomposition process of methane-I hydrate in inorganic salt (NaClKCl-CaCl2) and alcohols (methanol, ethylene glycol) solution was simulated at 265-273K. The effects of inhibitor type, concentration and temperature and pressure on hydrate decomposition were analyzed by calculating the structure, motion and energy change of each component in the simulated system. Moreover, the capacity of hydrate unit cell to bear inorganic salt ions, the adsorption of PVP Pe PEOU PVCap on hydrate surface and the effect on hydrate decomposition were studied, and the microcosmic mechanism of the inhibitor was discussed. The simulation results show that the liquid membrane formed by hydrate decomposition can delay the process of decomposition, and the inorganic salt ion can break through the structure of liquid membrane, shorten the time of decomposition stagnation, and the decomposition rate is proportional to the concentration of inorganic salt. The decomposition rate is not constant in the process of decomposition. The energy needed for hydrate decomposition is different, in which KCl energy is the largest, and when the concentration of CaCl_2 is more than 30wt%, the energy required is the lowest. The damage ability of ions to the unit cell is different (Ca ~ (2) K ~ (2) K ~ (2) Cl ~ (- 2) Na ~ (2). In alcohol solution, the structure of the liquid membrane formed is loose and the diffusion of water molecules can not be delayed. When the concentration of the solution is 20wt- 30wt%, the rate of hydrate decomposition is the highest. In the process of hydrate decomposition, the decomposition heat decreases gradually with the increase of concentration, and then increases gradually after 30 wt%. Compared with temperature, the volume of confined space has little effect on the decomposition process. The interaction energy of Kinetic inhibitor and hydrate surface is affected by the concentration and molecular weight. PVCap has the strongest ability to decompose hydrate. The inhibitor molecule strengthens the short range (2.5?) The order of the molecular structure of water.
【学位授予单位】：中国石油大学(华东)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE39

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