石英砂介质中甲烷水合物生成过程和相平衡的实验研究

为研究小梯度温度范围内甲烷水合物在石英砂介质中生成过程的热力学和动力学特性,开展了定容条件下273.75K、273.85K、273.95K3种恒温水浴体系的甲烷水合物生成实验。研究结果表明:(1)反应温度越低,釜内甲烷水合物生成过程中反应热释放越快,相比于273.95K的反应体系,273.75K体系的反应釜内首次温度上升值为0.9K,约为273.95K体系的6倍;(2)随反应温度的增加,水合物的生成量和转化率逐渐下降;(3)反应温度越低,甲烷水合过程的前期反应速率越大,气液界面和石英砂表面生成的水合物薄膜阻碍了甲烷气与水之间的进一步传递,使得甲烷的单位消耗速率随反应的进行呈阶梯型递减。通过石英砂介质内甲烷水合物的生成实验,以期为工业上气体水合物的合成、储存与运输提供借鉴。     

Nucleation of methane hydrate and ice in the emulsions of water in five kinds of crude oils

In this work the model which allowes to receive information about characteristics (number, content and relative activity) of heterogeneous nucleation centers in dispersed systems with metastable dispersed phase was used to treat the experimental results on the nucleation of methane hydrate and ice in the water-in-crude oil emulsions. More than ten types of nucleation centers differing from each other in activity was detected in the experiments. Hydrate and ice nucleation occured in the temperature intervals 264–269?K and 261–265?K, respectively.     

含冰甲烷水合物的应力与应变关系

对含冰甲烷水合物试样进行了三轴压缩试验,分析了与其应力、应变行为相关的起始屈服应变、起始屈服强度和起始屈服模量随围压和温度变化的关系;并利用Duncan-Chang双曲线模型获得含冰水合物的初始变形模量、极限偏主应力和破坏比,分析了它们与围压和温度的关系。结果表明,起始屈服应变、起始屈服强度、初始变形模量和极限偏主应力均随围压的增加和温度的降低而增加;起始屈服模量仅受温度影响;破坏比随围压的升高有降低的趋势,而随温度降低有增加的趋势;实验数据拟合结果表明,起始屈服应变、起始屈服强度和极限偏主应力分别与温度和围压呈线性关系,初始变形模量与温度和围压呈幂函数关系。     

Use of X-ray computed microtomography to understand why gels reduce relative permeability to water more than that to oil

X-ray computed microtomography (XMT) was used to investigate why gels reduce relative permeability to water more than that to oil in strongly water-wet Berea sandstone. XMT allows saturation differences to be monitored for individual pores during various stages of oil, water, and gelant flooding. The method also characterizes distributions of pore size, aspect ratio, and coordination number for the porous media. We studied a Cr(III) acetate–HPAM gel that reduced permeability to water (at S_or) by a factor 80–90 times more than that to oil (at S_wr). In Berea, the gel caused disproportionate permeability reduction by trapping substantial volumes of oil that remained immobile during water flooding (i.e., 43.5% S_or before gel placement versus 78.7% S_or after gel placement). With this high trapped oil saturation, water was forced to flow through narrow films, through the smallest pores, and through the gel itself. In contrast, during oil flooding, oil pathways remained relatively free from constriction by the gel.