Genetic mechanism of pyrolytically desorbed hydrocarbon
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摘要: 在油气化探技术研究中,热释烃测试数据具有烯烃含量比同碳数烷烃高、异构烷烃含量比同碳数正构烷烃高的反常特征,且这种特征随着热释温度的升高而更加明显。然而油气源及地表样品中的酸解烃、顶空间轻烃、游离烃、水溶烃都不具有这样的特征。有学者从不同角度对热释烃的反常特征加以解释,但都没有考虑样品所含有机质在真空和加热状态下会不会裂解、重排而生成烯烃的问题。依据3个地区地表土壤样品热释温度实验,根据其热释烃与有机碳相关性研究,并分别结合树叶有机质、土壤有机质热生烃实验结果,推断土壤样品中的热释烃成因机理为化学吸附轻烃的解吸叠加有机质的热裂解。热释温度160 ℃以下的热释烃主要为化学吸附轻烃的解吸,而热释温度160 ℃以上的热释烃主要为土壤中的有机质在真空条件下的热裂解。地热田的热作用可以促进围岩中有机质成烃,在一定程度上使有机质含量降低、轻烃含量增加,可据此进一步研究热释烃的地热指示意义。Abstract: In the geochemical exploration for oil and gas, the test data of pyrolytically desorbed hydrocarbons have the abnormal characteristics that the relative content of olefins is higher than that of alkanes with the same carbon number, and the relative content of isoparaffins is higher than that of normal alkanes with the same carbon number, and this feature becomes more obvious with the increase of temperature of pyrolytical desorption. On the other hand, the acid hydrolyzed hydrocarbons, headspace light hydrocarbons, free hydrocarbons, and water-soluble hydrocarbons in oil and gas sources and surface samples do not have such feature. The abnormal characteristics of pyrolytically desorbed hydrocarbons have been previously explained from different aspects, but whether the organic matters contained in the samples will crack and rearrange to generate olefins under vacuum and heating conditions has not been considered. Some experiments of pyrolytical desorption temperature of surface soil samples from three regions were carried out. The correlation between pyrolytically desorbed hydrocarbons and organic carbon was discussed. Combined with the pyrolytical desorption experiments of organic matter in leaf and soil, it was inferred that the pyrolytically desorbed hydrocarbons in soil samples mainly came from the desorption of chemically adsorbed light hydrocarbons (below 160℃) and the thermal cracking of organic matter (above 160℃). The thermal action of geothermal field can promote the hydrocarbon generation of organic matter in surrounding rocks, and to a certain extent, reduce the content of organic matter and increase the content of light hydrocarbons, which can be used for further study of geothermal indicating significances of pyrolytically desorbed hydrocarbons.
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Key words:
- pyrolytically desorbed hydrocarbons /
- genetic mechanism /
- olefins /
- organic matter /
- thermal cracking
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表 1 四川盆地新场气田上方土壤样品热释温度实验结果
Table 1. Pyrolytical desorption experiment results at different temperatures of soil samples above Xinchang gas field, Sichuan Basin
μL/kg 样号 热释温度/℃ 甲烷 乙烷 乙烯 丙烷 丙烯 异丁烷 正丁烷 异戊烷 正戊烷 B01 120 0.78 0.04 0.34 0.05 0.29 0.00 0.01 0.00 - 140 1.09 0.07 0.70 0.14 0.92 0.02 0.03 0.00 0.01 160 1.89 0.08 0.91 0.30 1.59 0.12 0.04 0.04 0.04 180 3.51 0.21 3.05 0.67 6.13 1.51 0.18 0.77 0.15 B02 120 1.02 0.05 0.41 0.07 0.41 0.01 0.03 0.00 0.01 140 1.68 0.12 1.27 0.27 1.92 0.04 0.06 0.03 0.05 160 2.96 0.14 2.31 0.60 4.35 0.34 0.12 0.20 0.15 180 5.30 0.30 5.51 1.02 10.87 1.65 0.23 0.85 0.22 B03 120 1.19 0.03 0.20 0.03 0.14 0.01 0.01 - - 140 0.95 0.04 0.49 0.09 0.64 0.01 0.02 - - 160 1.21 0.04 0.74 0.13 1.28 0.05 0.03 0.01 0.01 180 2.39 0.10 1.45 0.26 3.77 0.30 0.05 0.13 0.03 B04 120 0.71 0.02 0.22 0.03 0.15 0.00 0.01 - - 140 1.30 0.05 0.55 0.11 0.65 0.01 0.02 - - 160 1.69 0.07 0.93 0.22 1.53 0.07 0.04 0.02 0.03 180 3.55 0.22 3.05 0.53 6.80 0.63 0.13 0.29 0.09 B05 120 0.82 0.03 0.27 0.04 0.23 - - - - 140 1.43 0.06 0.65 0.12 1.03 0.02 0.02 - - 160 2.48 0.09 1.28 0.29 2.57 0.18 0.06 0.05 0.03 180 3.75 0.13 2.10 0.36 5.08 0.56 0.08 0.24 0.05 表 2 渤海湾盆地济阳坳陷垛石桥地区土壤样品热释烃温度实验结果
Table 2. Pyrolytical desorption experiment results at different temperatures of soil samples from Duoshiqiao area, Jiyang Depression, Bohai Bay Basin
μL/kg 样号 热释温度/℃ 甲烷 乙烷 乙烯 丙烷 丙烯 异丁烷 正丁烷 异戊烷 正戊烷 A160 160 1.88 0.17 2.10 0.32 0.77 0.43 0.06 0.06 - 180 9.04 0.56 6.63 1.57 4.58 6.59 0.30 2.71 0.01 200 22.99 1.38 18.24 3.69 23.52 16.02 0.95 8.00 0.63 A162 160 0.70 0.04 0.64 0.07 0.39 0.06 0.01 - - 180 2.55 0.21 2.25 0.19 2.14 0.59 0.06 0.43 - 200 10.98 0.29 5.53 0.43 3.60 1.17 0.09 2.10 - A164 160 2.32 0.17 2.35 0.54 0.41 0.52 0.05 0.07 - 180 8.90 0.60 7.04 1.69 3.15 4.00 0.30 1.27 0.42 200 20.45 1.09 11.64 2.45 7.54 6.76 0.44 1.54 0.12 A166 160 7.05 0.34 3.76 0.68 1.21 0.81 0.04 0.10 - 180 19.93 1.19 14.9 3.25 15.11 9.43 0.61 3.24 0.38 200 39.89 2.07 20.86 4.49 23.26 15.3 0.68 3.25 0.16 A168 160 1.32 0.09 1.99 0.29 1.02 0.48 0.06 0.14 0.01 180 5.62 0.23 3.63 0.60 3.15 2.39 0.15 1.03 0.11 200 15.86 0.56 8.46 1.18 9.08 4.64 0.28 1.44 0.14 表 3 同一样品不同温度下热释烃实验[10]
Table 3. Pyrolytical desorption experiment results of the same sample at different temperatures
μL/kg 热释温度/℃ 甲烷 乙烷 乙烯 丙烷 丙烯 异丁烷 正丁烷 异戊烷 正戊烷 150 1.39 0.03 0.21 0.09 0.23 0.42 0.03 0.12 0.07 200 3.20 0.12 2.98 0.20 3.01 0.07 0.03 0.01 - 250 10.57 0.27 15.28 0.50 14.72 0.98 0.19 0.01 0.09 290 164.70 1.93 357.29 2.01 110.72 3.95 1.50 2.70 0.30 320 780.93 20.95 1 938.70 14.08 607.85 9.98 6.01 3.96 1.29 表 4 总有机碳含量与热释烃相关系数
Table 4. Correlations between TOC and pyrolytically desorbed hydrocarbons
样品来源 甲烷 乙烷 乙烯 丙烷 丙烯 异丁烷 正丁烷 异戊烷 正戊烷 四川新场气田 0.17 0.27 0.77 0.60 0.79 0.64 0.69 0.60 0.55 青海木里 0.51 0.28 0.5 0.51 0.48 0.50 0.33 0.47 0.34 南黄海海域 0.67 0.76 0.74 0.75 0.55 0.61 0.66 0.55 0.53 表 5 碳酸盐、硅酸盐与烃类指标相关系数[12]
Table 5. Correlation between carbonate, silicate and hydrocarbon indexes
烃类 ΔC CaO Fe2O3 MnO MgO Al2O3 SiO2 有机碳 酸解烃甲烷 0.61 0.67 0.11 0.21 0.26 -0.14 -0.20 0.11 酸解烃重烃 0.38 0.74 0.48 0.57 0.03 -0.33 -0.39 0.10 热释烃甲烷 -0.12 0.18 0.54 0.22 -0.49 -0.61 -0.71 0.72 热释烃重烃 0.02 0.22 0.41 0.12 -0.40 -0.53 -0.64 0.71 表 6 腐烂樟树叶的热释烃量
Table 6. Pyrolytically desorbed hydrocarbons from decayed camphor leaves
μL/kg 热释温度/℃ 甲烷 乙烷 乙烯 丙烷 丙烯 异丁烷 正丁烷 反-2-丁烯 1-丁烯 异丁烯 顺-2-丁烯 异戊烷 正戊烷 80 6.40 0.66 3.00 0.55 1.14 0.03 0.13 - 0.04 0.42 - 0.05 0.25 100 22.16 2.44 10.20 2.41 4.74 0.08 0.46 0.06 0.17 1.88 0.07 0.16 1.31 120 67.65 8.28 35.29 8.26 14.90 0.29 0.93 0.13 0.43 5.94 0.15 0.30 1.76 140 140.67 12.61 90.38 12.95 28.79 0.60 1.14 0.17 0.63 10.75 0.25 0.27 1.72 160 324.35 27.51 187.87 27.24 65.53 1.62 2.81 0.76 2.14 31.47 0.91 0.69 4.88 180 728.62 49.52 317.47 57.53 185.97 5.79 10.85 5.56 13.68 148.71 6.39 3.40 20.17 表 7 干樟树叶的热释烃量
Table 7. Pyrolytically desorbed hydrocarbons from dried camphor leaves
μL/kg 热释温度/℃ 甲烷 乙烷 乙烯 丙烷 丙烯 异丁烷 正丁烷 反-2-丁烯 1-丁烯 异丁烯 顺-2-丁烯 异戊烷 正戊烷 80 26.64 4.11 7.76 1.10 1.04 0.24 0.21 - 0.07 1.00 - - 0.86 100 48.57 8.40 19.24 3.98 2.39 0.39 0.64 0.02 0.15 2.47 0.02 0.06 3.74 120 198.49 39.32 81.21 17.97 10.10 1.26 1.45 0.07 0.29 12.35 0.03 0.02 4.85 140 451.42 73.29 182.91 57.96 35.12 3.69 4.58 0.53 1.25 81.15 0.62 0.22 15.98 160 874.27 132.85 301.19 76.67 57.20 8.46 11.35 2.46 3.63 427.34 2.27 0.86 41.81 180 1647.09 229.09 529.94 198.21 122.18 13.58 26.60 10.20 10.59 1 179.96 9.96 1.64 122.39 表 8 土壤样品经不同酸解、热释处理后的热释烃含量
Table 8. Desorbed hydrocarbon contents of soil samples after acidolysis and pyrolysis treatments
μL/kg 样号 处理方式 甲烷 乙烷 乙烯 丙烷 丙烯 异丁烷 正丁烷 异戊烷 正戊烷 22 直接热释T0 25.0 0.5 8.1 1.0 11.0 3.8 0.6 1.5 0.2 有机碳热释T1 25.3 0.6 9.6 1.2 12.5 7.3 1.0 4.1 0.8 23 直接热释T0 78.5 4.3 17.2 12.7 40.7 27.1 3.3 11.2 2.0 有机碳热释T1 70.0 9.2 18.5 22.8 53.7 54.0 8.4 27.4 4.6 24 直接热释T0 48.8 2.2 10.3 4.2 19.1 5.1 0.8 1.2 - 有机碳热释T1 34.4 3.1 10.9 6.2 23.4 13.5 1.7 3.2 0.3 25 直接热释T0 33.0 2.2 10.6 7.7 19.7 15.2 2.8 4.8 0.6 有机碳热释T1 31.3 1.5 9.8 4.1 14.0 7.7 2.4 2.6 1.5 -
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