化学剂作用下气体水合物分解特性研究

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	化学剂作用下气体水合物分解特性研究
其他题名	Study on Dissociation Features of Gas Hydrate In the Presence of Chemicals
	万丽华
导师	李小森
	2009-01-05
学位授予单位	中国科学院广州能源研究所
学位授予地点	广州能源研究所
学位名称	博士
关键词	气体水合物开采分解分子动力学模拟过氧化氢溶液热力学抑制剂
摘要	为了以经济、安全、有效的方式开采水合物，热力法与注化学试剂法相结合的开采方法，被认为是最有潜力的开采方法之一。本文利用天然气水合物一维开采模拟系统，注入热的NaCl水溶液，进行甲烷水合物分解过程和开采模拟研究。结果表明，在热NaCl溶液作用下，水合物出现降温吸热分解过程，NaCl浓度愈大、水合物分解过程越短，温降幅度愈大。气体产出过程可以分为自由气产出阶段，水合物分解阶段以及水合物分解结束后常规气藏的气体产生阶段，而NaCl的加入可以提高水合物分解阶段的产气速率。在自由气产出阶段基本没有水产出，在水合物分解阶段，产水速率稍高于注水速率，水合物分解结束后，产水速率等于注水速率。同时，研究了热NaCl水溶液作用下的开采热效率和能源效率。实验结果表明，注入热水中加入NaCl可以提高热效率和能量效率，且当采用较低的注入温度,这种提高更加明显。为了提高开采效率，探索利用过氧化氢（Hydrogen Peroxide,HP）氧化剂原位氧化甲烷放热分解天然气水合物的新型开采方法。首先展开HP是否能够参与水合物构建的研究，通过分子动力学模拟(MD)研究了客体分子含HP的假想水合物在277K温度下的稳定性。模拟结果显示，客体分子含HP的假想水合物在模拟条件下不能够稳定存在，HP分子不参与水合物构建。然后采用MD研究了HP溶液作用下甲烷水合物晶体分解特性。系统了分析甲烷水合物在过氧化氢水溶液作用下由晶态向液态转变过程的机理，对比了相同摩尔浓度乙二醇(ethylene glycol,EG)溶液作用下甲烷水合物分解变化规律，结果表明HP与水合物热力学抑制剂EG一样对甲烷水合物分解具有促进作用，HP与EG一样可为热力学抑制剂，当然，HP为热力学抑制剂需要通过相平衡实验研究以进一步确认。采用NVT系综分子动力学方法模拟研究277.0K，11.45mol•L-l热力学抑制剂EG溶液作用下甲烷水合物微观分解过程。模拟显示，固态水合物的分解从晶格扭曲变形开始，之后笼形框架结构破裂，最后形成笼形结构碎片。同时，已经分解的甲烷水合物在外层形成水膜，包裹里层正在分解的甲烷水合物，增大里层甲烷水合物分解传质阻力。
其他摘要	Among the recovery methods of natural gas production from hydrate reservoir, the thermal stimulation is safely and effectively capable of producing substantial amounts of natural gas, and it will be more effective combining with the chemical injection. The work investigates the dissociation behavior of methane hydrates in a one-dimensional experimental apparatus under hot brine (NaCl solution) stimulation. The results showed that the process of methane hydrate dissociation accompanied the temperature decrease and endothermal change with the injection of NaCl solution. The duration of the hydrate dissociation is shortened and the degree of the temperature drop increases with the increase of the brine concentration. In addition, the characteristics of the dissociated gas and water from methane hydrates in the porous sediment under hot brine stimulation were also investigated. The experimental results showed that the gas production process can be generally divided into three stages: free gas production, hydrate dissociation and general gas reservoir production. The rate of hydrates dissociation can be enhanced by the addition of NaCl. In the stage of free gas production, there was little water production. In the stage of hydrate dissociation, the rate of water production is slightly higher than that of water injection. In the final stage, the dissociation of hydrate has completed, and the rate of water production is equal to that of water injection.Thermal efficiency and energy ratio for the hydrate production can be enhanced by injecting hot brine solution, and the enhance effectiveness is quite good with the injection of high brine concentration at the relative low temperature. In order to investigate the novel natural gas hydrate production method involving methane hydrate deposits dissociation in-situ originated from gas oxygenation by hydrogen peroxide as an oxidizer to enhance the recovery efficiency, first of all, it was determined whether hydrogen peroxide forms hydrate as a former of structure I at elevated pressures in this work, that is, the stabilities of gas hydrate with structure I for hydrogen peroxide and mixture of methane and hydrogen peroxide at 277K were studied using NVT molecular dynamics simulations. The results show that the investigated hydrates can not be stably in existence,thus making it that hydrogen peroxide can not take part in clathrate formation.Then, the characteristics of the decomposition of methane hydrate in the presence of hydrogen peroxide solution were investigated using the molecular dynamics simulation. The mechanism of the transformation process from the solid hydrate to the liquid was analyzed with the effect of hydrogen peroxide (HP) solution. In addition, the effect of ethylene glycol (EG) with the same molar concentration with HP on the methane hydrate dissociation was also studied. It is deduced that hydrogen peroxide is potentially thermal inhibitor of hydrates from hydrogen peroxide promoting well the hydrate dissociation and not taking part in clathrate formation. However, to confirm this hypothesis, direct measurements of the hydrate phase are needed, i.e., by phase equilibrium experiment of hydrate forming from hydrogen peroxide solution. The dissociation of methane hydrates in the presence of ethylene glycol of 11.45 mol•L-l at 277.0 K was studied using NVT molecular dynamics simulations. The results showed that in the process of the hydrate dissociation, the distortion of the lattice structure of hydrate occurs firstly, and then it is evolved from fractured frame to fractional fragment. Finally, water molecule involving in the hydrate construction exists in the form of liquid state. In addition, the dissociating layer inside has been coated by the liquid film formed from dissociated water molecules outside. This film makes mass transfer performance of the molecules inside poor during the process of the hydrate dissociation.
页数	109
语种	中文
文献类型	学位论文
条目标识符	http://ir.giec.ac.cn/handle/344007/5826
专题	中国科学院广州能源研究所
推荐引用方式 GB/T 7714	万丽华. 化学剂作用下气体水合物分解特性研究[D]. 广州能源研究所. 中国科学院广州能源研究所,2009.

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