Oil Migration and Accumulation Mechanisms for Heavy Oils in North Steep Slope of Dongying Depression, Eastern China
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摘要: 东营凹陷北部陡坡带的王庄—宁海地区发现了大量稠油, 但原油的成因及其成藏机理仍不甚了解.在以往原油成因与油源调查基础上, 利用非烃含氮化合物及包裹体均一化温度对该区进行油气运移方向与相对距离、成藏时间与期次的分析.结果表明, 东营凹陷北部带原油具有由南而北的运移分馏效应, 反映北部陡坡带原油来自南部的利津洼陷; 王庄—宁海地区原油总体具有由东而西的运移分馏效应, 其东、西两侧各有一主要油气注气点.王庄—宁海原油烃类与非烃组成与分布特征揭示该区油气具有混合聚集特征.包裹体测试反映王庄—宁海地区油藏主要为晚期成藏, 距今小于5Ma; 而靠近生油中心地带包裹体具有早期成藏的记录(± 36Ma).Abstract: A large amount of heavy oils are discovered in the north steep slope (NSS) of the Dongying depression, the Bohai Bay basin, Eastern China, but the mechanism of oil accumulation for this oil pools is still not well understood. Based on detail investigation of the composition for the oils and their source rocks, pyrrolic nitrocompounds and fluid inclusions have been analyzed to trace the process of oil migration and accumulation in the Wangzhuang-Ninghai region. The results show that apparent migration effects of nitrogen compounds within the oils from south to north, indicate the oils in the north steep slope originated mainly from the Lijing sag in the Dongying depression. Obviously, migration effects from east to west observed in the Wangzhuang-Ninghai area indicate two main charging points respectively in the eastern and western areas. Composition of alkanes and non-alkanes and their distribution as well as pyrrolic nitrogen compounds show the origin of mixing of the oils. Alkanes with slight and/or no biodegradation and 25-norhopanes with strong biodegradation are observed in same oils, which indicates possibly multiple oil charging periods and/or redistribution of the oils due to tectonic movement. Two periods of oil formation and accumulation have been identified as evidenced from fluid inclusions. Oil pools in the Wangzhuang-Ninghai region were formed within 5 (?) Ma before present. The oils generated in nearly 36 (?) Ma ago as evidenced from inclusions in reservoir near the Lijing sag. A number of faults, several unconformities and a series of well developed fans with coarse sands and conglomerate in the NSS are taken as favored migration pathways for hydrocarbon in the study (area).
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Key words:
- heavy oil /
- nitrogen compounds /
- fluid inclusion /
- oil migration /
- north steep slope
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表 1 部分原油主要含氮化合物运移指标
Table 1. Migration parameters of nitrogen compounds in the oils of the north steep slope in Dongying depression
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Chen, J. Y., Liu, C. Y., Zhang, S. L., et al., 1997. Composition of the biomarkers in crude oils is the reflection of pool-formation history. Earth Science—Journal ofChina University of Geosciences, 22 (6): 97-102 (in Chinese with English abstract). Chen, M., 1995. Response of pyrrolic and phenolic compounds to petroleum migration and in-reservoir processes[Dissertation]. University of Newcastle, U.K. . Li, M., Larter, S.R., 1993. Interactions of organic nitrogen species with mineral, water and organic networks: Implications to petroleum geochemistry. Paper presented at the 205th American Chemical Society Meeting(Denver), Division of Geochemistry, American Chemical Society, Abstract Paper, 89. Li, M., Larter, S. R., Stoddart, D., et al., 1992. Practical liquid chromatographic separation schemes for pyrrolic and pyridinic nitrogen aromatic heterocycle fractions from crude oils suitable for rapid characterisation of geochemical samples. Analytical Chemistry, 64: 1337-1344. doi: 10.1021/ac00037a007 Li, M., Larter, S.R., Stoddart, D., et al., 1995. Fractionation of pyrrolic nitrogen compounds in petroleum during migration: Derivation of migration-related geochemical parameters. In: Cubit, J.M., England, W.A., eds., The Geochemistry of Reservoirs. Geol. Soc. Spec. Publ., 86: 103-123. Li, S.M., 1999. Nonhydrocarbons geochemistry: Isolation, distribution and application of NSO compounds. Geological Publishing House, Beijing, 74-86(in China). Li, S. M., Wang, T. G., Zhang, A. Y., et al., 1999. Characteristics of pyrrolic compound in crude oils and its significane. Acta Sedimentologic Sinica, 17 (2): 312-317 (in Chinese with English abstract). Li, S. M., Pang, X. Q., Li, M. W., et al., 2002. Characteristics of pyrrolic nitrogen compounds and their geochemical significance in oils and rocks of Bamianhe oilfield, eastern China. Geochimila, 31 (1): 1-7 (in Chinese with English abstract). Li, S. M., Wang, T. G., Zhang, A. Y., 2000. Effect of maturity on pyrrolic nitrogen compounds. Scientia Geologica Sinica, 9 (2): 227-236. Snyder, L. R., Buell, B. E., 1968. Nitrogen and oxygen compound types in petroleum: A general separation scheme. Analytical Chemistry, 40: 1295-1302. doi: 10.1021/ac60264a004 Wang, T. G., Li, S. M., Zhang A. Y., et al., 2000. Application of pyrrolic compound in oil-gas migration at Lunnan oil- field. Acta Geologica Sinica, 74 (1): 85-92 (in Chinese with English abstract). Zhu, Y. M., Fu, J. M., Sheng, G. Y., et al., 1997. Geochemical significance of pyrrolic nitrogen compounds in the oils of Tarim basin. Chinese Science Bulletin, 42 (23): 2528-2531 (inChinese). doi: 10.1360/csb1997-42-23-2528 陈建渝, 刘从印, 张树林, 等, 1997. 原油中生物标志物的组成是成藏史的反映. 地球科学———中国地质大学学报, 22 (6): 97-102. https://www.cnki.com.cn/Article/CJFDTOTAL-DQKX801.021.htm 李素梅, 1999. 非烃(吡咯类、酚类) 地球化学研究: 方法、分布特征与应用. 北京: 地质出版社, 74-86. 李素梅, 王铁冠, 张爱云, 等, 1999. 原油中吡咯类化合物的地球化学特征及其意义. 沉积学报, 17 (2): 312-317. doi: 10.3969/j.issn.1000-0550.1999.02.025 李素梅, 庞雄庞, 黎茂稳, 等, 2002. 低熟油、烃源岩中含氮化合物分布规律及其地球化学意义. 地球化学, 31 (1): 1-7. https://www.cnki.com.cn/Article/CJFDTOTAL-DQHX200201000.htm 王铁冠, 李素梅, 张爱云, 等, 2000. 应用含氮化合物探讨轮南油田油气运移. 地质学报, 74 (1): 85-92. https://www.cnki.com.cn/Article/CJFDTOTAL-DZXE200001010.htm 朱扬明, 傅家谟, 盛国英, 等, 1997. 塔里木盆地不同成因原油吡咯氮化合物的地球化学意义. 科学通报, 42 (23): 2528-2531. doi: 10.3321/j.issn:0023-074X.1997.23.015