倾斜管中CO2水合物生成及堵管实验研究

研究倾斜管内气液两相流的堵管机理对于保证油气的安全输送起到至关重要的作用。因此,在高压可视水合物实验环路上开展了倾斜管中水+CO₂体系下的水合物堵管实验,探究了压力、流速等因素对CO₂水合物浆液流动和堵管时间的影响。实验结果表明,在流速分别为3 L/min或5 L/min或7 L/min的条件下,初始压力为2.7 MPa、3.0 MPa和3.3 MPa时,水合物浆液流动时间分别为451 s、336 s、303 s或632 s、510 s、391 s或740 s、657 s、512 s。由此可知,初始压力越大,水合物浆液的流动时间越小,管路越容易发生堵塞。在初始压力分别为2.7 MPa或3.0 MPa或3.3 MPa的条件下,流速为3 L/min、5 L/min和7 L/min时,水合物浆液流动时间分别为451 s、632 s、740 s或336 s、510 s、657 s或303 s、391 s、512 s。由此可知,初始流速越大,水合物浆液的流动时间越大,管路越不易发生堵塞。因此,可以通过减小初始压力和增大初始流速来有效减小管路堵管趋势。     

含抑制剂体系下天然气水合物形成预测模型的建立与应用

油气水混相在开采与运输过程中易生成天然气水合物,预测其形成条件可保障油气田的安全运行。建立了包含超过1500个数据点的广泛数据库和基于PSO-LSSVM的含抑制剂天然气水合物形成解离模型,与BP神经网络模型模拟结果进行了对比分析,并在荔湾气田现场管道进行了预测应用。结果表明,LSSVM模型通过PSO算法优化后确定的正则化参数为321.1523642521、核参数为1.0210368871948。BP神经网络模型和PSO-LSSVM模型的平均相对误差分别为1.92%和0.49%,说明PSO-LSSVM模型的预测能力更强。以纯水为基础介质时,BP神经网络模型和PSO-LSSVM模型均可较准确地预测水合物形成,但以含热力学抑制剂水溶液为基础介质时,PSO-LSSVM模型具有更优秀的表现。PSO-LSSVM模型对于荔湾气田现场生产具有较强的适用性,可为甲醇注入量的确定和现场安全运行策略的制定提供理论依据。     

天然气水合物开发利用面临的问题及应对策略

为了使天然气水合物成为我国的后续替代能源,提出了需要认真对待和考虑解决的四个问题:充分认识天然气水合物的本质;科学评价我国天然气水合物资源量;积极开发自主知识产权的开采技术;兼顾天然气水合物相关技术的开发。同时还阐述了解决这些问题的策略。     

Feasibility of trichlorofluoromethane (CCl3F,R11) heptadecahydrate as a heat storage material

Trichlorofluoromethane (CCl₃F, R11) heptadecahydrate, which melts at 8.5°C with a heat of fusion of 274 kJ/kg (65.4 cal/g), was investigated as a latent heat storage material. Addition of nonionic surfactant, 2 wt% to water in R11 hydrate, increased the formation rate of the hydrate about 4 times which is sufficient for practical use. Phase separation of R11 was prevented effectively in a gel matrix formed by polyacrylamide (PAA) or gelatin. The PAA gel containing the hydrate-surfactant had an apparent latent heat of fusion of 167–209 kJ/kg (40–50 cal/g), repeating phase change successfully over 100 cycles without deterioration in a heat cycle test (0–20°C, 5 cycles/day). Tetrabutyl ammonium fluoride hydrate [(C₄H₉)₄NF 34.4 H₂O] was found effective as a nucleating agent.     

Influence of novel shrinkage-reducing polycarboxylate superplasticizer on the nature of calcium–silicate–hydrates

Currently, a novel shrinkage-reducing polycarboxylate superplasticizer (SR-PCA) is used to control cementitious shrinkage. To clarify its mechanism when applied in cementitious materials, the influence of SR-PCA on the composition, morphology, and structure of synthetic calcium–silicate–hydrate (C–S–H), together with the interaction between SR-PCA and C–S–H at the atomic level, is investigated. For comparison, a commercial polycarboxylate superplasticizer (PCA) is also employed. The results show PCA and SR-PCA can adsorb on the C–S–H surface rather than intercalate into the layers. Compared with PCA, SR-PCA has a milder impact on C–S–H crystallinity. SR-PCA refines the pore structure of C–S–H drastically, whereas PCA loosens the structure by increasing the mesopore volume. In addition, the adsorption effect of SR-PCA on the C–S–H surface is less significant than that of PCA. At the atomic level, this less adsorption of SR-PCA is attributed to the lower adhesion energy of the C–S–H/SR-PCA interface due to the weaker Ca–O bond strength.     

基于水氯镁石合成水合硅酸镁及其在镁质浇注料的应用

水氯镁石是一种非常具有应用前景的镁盐资源,其储量丰富,成本低廉。以青海盐湖水氯镁石和水玻璃合成不同MgO/SiO₂摩尔比(0.5:1,1:1,1.5:1)的水合硅酸镁(M-S-H)凝胶,采用XRD、SEM、红外和核磁共振等测试手段研究M-S-H的合成机理和结构特征,进而将合成的M-S-H与硅微粉复合制备镁质浇注料,探究M-S-H结构对浇注料结合特性的影响规律。结果表明:不同MgO/SiO₂摩尔比的M-S-H呈层状堆叠结构,MgO/SiO₂摩尔比为1:1时M-S-H的层间自由水少,结晶度最高;M-S-H替代部分硅微粉制备镁质浇注料能显著提高1 550 ℃热处理后浇注料的力学性能,其中MgO/SiO₂摩尔比为1:1的M-S-H复合硅微粉制备的镁质浇注料综合性能最佳,与添加6%(质量分数)硅微粉制备的镁质浇注料相比,其常温抗折强度和高温抗折强度分别提高75%和8%。     

三种麻醉剂对小鼠离体子宫平滑肌收缩性影响的比较

目的探讨氨基甲酸乙酯、戊巴比妥钠、水合氯醛3种麻醉剂对小鼠离体子宫平滑肌收缩性的影响。方法将制备的小鼠离体子宫标本置入37℃低钙洛氏液，用BL-410生物机能实验系统记录加麻醉剂前、后及更换低钙洛氏液后各10min的收缩曲线，测量收缩频率和收缩强度，计算运动指数。结果3种麻醉剂对子宫平滑肌的收缩频率、收缩强度、运动指数都有明显的抑制作用，去除麻醉剂后都可恢复收缩。水合氯醛的抑制作用最强，为完全抑制，去除麻醉剂后很长时间才能恢复收缩；戊巴比妥钠的抑制作用最弱，去除麻醉剂后很快恢复收缩，且收缩强度和运动指数的恢复率都最高。3种麻醉剂在抑制率、恢复率上大部呈现量-效关系。结论在以动物子宫为研究对象的实验中宜用戊巴比妥钠作为麻醉剂。     

轻稀土离子水合物Re3+(H2O)n(n=1~12,Re=La、Ce、Pr、Nd)的DFT研究

采用Material studio的DMol3模块研究了La³⁺、Ce³⁺、Pr³⁺、Nd³⁺四种离子的水合物Re³⁺(H₂O)_n(n=1~12),分析了几何优化后的构型的几何结构、结合能、前线轨道、电荷、振动情况。结果表明:La³⁺、Ce³⁺、Pr³⁺、Nd³⁺四种轻稀土离子第一水化层的最小水合数分别为4、6、7、7;在相同水合数条件下,Re—O的平均键长大小顺序为La>Ce>Pr>Nd,Re³⁺(H₂O)₁₀的Re—O平均键长约为2.6?,轻稀土离子水合物的水化层半径约为3.22~3.59?。轻稀土离子的水化反应为放热反应,当水分子配位数相同时,结合能大小顺序为La>Ce>Pr>Nd。电荷分析结果显示,水合反应过程中稀土离子得到电子,当第一水化层填满后,Re³⁺(H₂O)_n性质逐渐趋于稳定,Re离子的电荷量在2e左右。前线轨道分析结果显示,不同于离子半径的变化,四种稀土离子自身的硬度大小顺序为La>Nd>P>Ce。模拟的La³⁺(H₂O)_n的红外光谱显示,随着水分子数量的增加,V_sym和V_asym峰发生蓝移;当n大于10时,V_sym和V_asym峰不再发生蓝移,说明第一水化层外的水分子没有与La离子发生反应。     

采空区对CO2置换开采海域天然气水合物置换效果影响的实验研究

为揭示固体开采形成的采空区对CO₂置换开采天然气水合物置换效果的影响,开展了含采空区储层与完整储层的CO₂/N₂置换开采不同天然气水合物饱和度对比实验研究。结果表明:对于水合物饱和度分别为30%和45%的试样,含采空区储层较完整储层的CH₄置换率分别提高了5.5%和9%,单位体积CO₂封存量分别提高了26.5%和39.8%。采空区的存在提高了置换介质与天然气水合物的摩尔比率,从而提供了更高的置换驱动力;且在较高水合物饱和度试样中采空区还会提高置换介质的扩散作用,导致含采空区储层的置换效果好于完整储层。因此,在固体开采后进一步进行CO₂置换开采,可以提高置换开采效率,同时有助于碳封存与地层稳定,是一种潜在的海域天然气水合物安全、绿色开采模式。     

Fly ash and slag cement slurry containing microencapsulated phase change materials: Characterization and application

Based on the low hydration heat and temperature rise requirements of cement slurry used in natural gas hydrate layer, two novel microencapsulated phase change materials (MPCM‐1 and MPCM‐2) with different melting point were designed and synthesized; then, the heat evolution of cement slurry was controlled by MPCM‐1 and MPCM‐2 through physical means; the decomposition of hydrates was avoided. Before synthesizing MPCM‐1 and MPCM‐2, the micromorphology, particle size, and distribution of paraffin wax emulsion were studied. Then, the MPCM‐1 and MPCM‐2 containing paraffin wax with urea formaldehyde resin shell was synthesized by in situ polymerization, and the chemical structure and performances were investigated. The melting point of MPCM‐1 and MPCM‐1 is 23.09°C and 35.85°C; the phase change enthalpy is 97.49 and 85.69 J/g. The MPCM‐1 and MPCM‐2 were added into cement slurry, and the controlling effects on heat evolution were studied. As a result, it was found that the hydration heat and temperature rise of cement slurry were successfully reduced by using MCPM‐1 and MPCM‐2. Simultaneously, the investigations of fly ash and slag cement slurry were accomplished. Moreover, the fly ash and slag cement slurry containing microencapsulated phase change materials was prepared. It was shown that the 24 and 48‐hour hydration heat were reduced by 1.10 × 10⁵ and 10.5 × 10⁵ J, respectively.