In recent years, the Nanpu Sag in the Bohai Bay Basin in eastern China has experienced great discoveries in exploration, and has become a sag most rich in oil and gas in the basin. However, the early evaluation believed that the source rocks were of low quality. Based on numerous samplings and analyses, this paper finds that Es34 (the fourth sub-section of the third member of the Paleogene Shahejie Formation) is a high-quality hydrocarbon source rock, its TOC is above 5%. The thickness of high-quality hydrocarbon source rocks is 100 m and that of effective hydrocarbon source rocks about 250 m. The main buried depth of hydrocarbon source rocks is more than 3500 m, vitrinite reflectance (Ro) is more than 0.8%. The amorphous body and algae are an important source of organic matter in the hydrocarbon source rocks. The rocks are enriched with layers of clay and fine-grained calcite, which are the result of seasonal water stratification. The organic layer formed by algae breaking out and settlement is the main source of the organic-rich mudstone layer in Es34 in the Nanpu Sag. The biomarkers in Es34 reveal that the Es34 oil shale has a higher content of 4-methyl steranes, which is significantly different from that in other source rocks. In addition, a detailed comparison of biomarkers and isotopes in the Es34 oil shale and oil suggests that the oil in the Nanpu Sag comes mainly from the Es34 source rock, which is an object of future exploration.
1. Zhao, W. Z., Zhang, G.Y., Wang, H. J. New achievements of petroleum geology theory and its significances on expanding oil and gas exploration field. Acta Petrolei Sin., 2005, 26(1), 1–7 (in Chinese with English abstract).
2. Zhou, H. M., Dong, Y. X., Xie, Z. A. Precise Exploration of Fault-Depression Basin – Practice and Understanding of Precise Exploration of Napu Depression, Bohai Bay Basin. Petroleum Industry Press, Beijing, 2004 (in Chinese).
3. Zhou, C. N. Geological theory and exploration technology for lithostratigraphic hydrocarbon reservoirs. Petroleum Exploration and Development, 2007, 34(2), 2–5 (in Chinese with English abstract).
4. Jin, Q., Wang, R., Zhu, G. Y., Zeng, Y., Rong, Q. H. The lacustrine Liangjialou fan in the Dongying depression, eastern China: deep-water reservoir sandstones in a non-marine rift basin. J. Petrol. Geol., 2005, 28(4), 397–412.
http://dx.doi.org/10.1111/j.1747-5457.2005.tb00090.x
5. Zhu, G. Y., Zhang, S. C., Liu, K. Y., Yang, H. J., Zhang, B., Su, J., Zhang, Y. G. A well-preserved 250 million-year-old oil accumulation in the Tarim Basin, western China: Implications for hydrocarbon exploration in old and deep basins. Mar. Petrol. Geol., http://dx.doi.org/10.1016/ j.marpetgeo.2012.12.001.
6. Zhu, G. Y., Zhang, S. C., Su, J., Huang, H. P., Yang, H. J., Gu, L. J., Zhang, B., Zhu, Y. F. The occurrence of ultra-deep heavy oils in the Tabei Uplift of the Tarim Basin, NW China. Org. Geochem., 2012, 52, 88–102.
http://dx.doi.org/10.1016/j.orggeochem.2012.08.012
7. Zhu, G. Y., Jiang, N. H., Su, J., Yang, H. J., Hu, J. F., Cui, J. Distribution and implication of adamantane in crude oils in Lunnan area, Tarim basin in China. Energ. Explor. Exploit., 2012, 30(6), 957–970.
http://dx.doi.org/10.1260/0144-5987.30.6.957
8. Zhu, G. Y., Cui, J., Su, J., Yang, H. J., Zhang, B., Hu, J. F., Zhu, Y. F. Accumulation and Reformation of Silurian Reservoir in the Northern Tarim Basin. Acta Geol. Sin-Engl., 2012, 86(1), 209–225.
9. Zhu, G. Y., Zhang, S. C., Huang, H. P., Liang, Y. B., Meng, S. C., Li, Y. G. Gas genetic type and origin of hydrogen sulfide in the Zhongba gas field of the western Sichuan Basin, China. Appl. Geochem., 2011, 26(7), 1261–1273.
http://dx.doi.org/10.1016/j.apgeochem.2011.04.016
10. Bertrand, P., Lallier-Verges, E., Boussafir, M. Enhancement of accumulation and anoxic degradation of organic matter controlled by cyclic productivity: a model. Org. Geochem., 1994, 22(3–5), 511–520.
http://dx.doi.org/10.1016/0146-6380(94)90123-6
11. Derenne, S., Largeau, C., Brukner-Wein, A., Hetenyi, M., Bardoux, G., Mariotti, A., Origin of variations in organic matter abundance and composition in a lithologically homogeneous maar-type oil shale deposit (Gérce, Pliocene, Hungary). Org. Geochem., 2000, 31(9), 787–798.
http://dx.doi.org/10.1016/S0146-6380(00)00093-0
12. Carroll, A. R., Bohacs, K. M. Stratigraphic classification of ancient lakes: balancing tectonic and climatic controls. Geology, 1999, 27(2), 99–102.
http://dx.doi.org/10.1130/0091-7613(1999)027<0099:SCOALB>2.3.CO;2
13. Carroll, A. R., Bohacs, K. M. Lake-type controls on petroleum source rock potential in nonmarine basin. Am. Assoc. Petr. Geol. B., 2001, 85(6), 1033–1053.
14. Jin, Q., McCabe, P. J., Genetic features of petroleum systems in rift basins of eastern China. Mar. Petrol. Geol., 1998, 15(4), 343–358.
http://dx.doi.org/10.1016/S0264-8172(98)00017-8
15. Zhu, G. Y., Jin, Q. Study on source rock heterogeneity – a case of Nu-38 well in Dongying depression. Acta Petrolei Sin., 2002, 23(5), 34–39 (in Chinese with English abstract).
16. Zhu, G. Y., Jin, Q. Geochemical characteristics of two sets of excellent source rocks in Dongying depression. Acta Sedimentologica Sinica, 2003, 21(3), 506–512 (in Chinese with English abstract).
17. Zhu, G. Y, Jin, Q., Zhang, S. C., Dai, J. X., Zhang, L. Y., Li, J., Distribution characteristics of effective source rocks and their control on hydrocarbon accumulation: a case study from the Dongying Sag, Eastern China. Acta Geol. Sin-Engl., 2004, 78(6), 1275–1288.
18. Zhu, G. Y., Gu, L. J., Su, J., Dai, J. X., Ding, W. L., Zhang, J. C., Song, L. C. Sedimentary association of alternated mudstones and tight sandstones in China’s oil and gas bearing basins and its natural gas accumulation. J. Asian Earth Sci., 2012, 50, 88–104.
http://dx.doi.org/10.1016/j.jseaes.2012.01.008
19. Li, S. M., Pang, X. Q., Wan, Z. H., Mixed oil distribution and source rock discrimination of the Nanpu depression, Bohaibay basin. Earth Science (Journal of China University of Geosciences), 2011, 36(6), 1064–1072 (in Chinese with English abstract).
20. Gang, W. Z., Wu, Y., Gao, G., Ma, Q., Pang, X. Q., Geochemical features and geologic significances of source rocks in Nanpu Sag, Bohai Bay Basin. Petroleum Geology & Experiment, 2012, 34(1), 57–61 (in Chinese with English abstract).
21. Wang, Z. J., Ma, Q., Zhao, Z. X., Xia, J. S., Zhang, Y. C., Liu, Y. C., Wang, J. W. Natural gas origin and gas accumulation model for deep volcanic rocks in Nanpu Sag, Bohai Bay Basin. Acta Petrolei Sin., 2012, 33(5), 772–780 (in Chinese with English abstract).
22. Zhang, C. M., Liu, X. F. The boundary faults and basin-formation mechanism of Nanpu Sag. Acta Petrolei Sin., 2012, 33(4), 581–587 (in Chinese with English abstract).
23. Zhu, G. Y., Zhang, S. C., Wang, Y. J., Wang, Z. J., Zheng, H. J., Xiong, Y., Dong, Y. X., Wang, X. D., Zhang, B. High quality source rocks and hydrocarbon accumulation in Nanpu Sag, Bohai Bay basin, China. Acta Geol. Sin., 2011, 85(1), 97–113.
24. Liu, Y. H., Liu, X. Evaluation methods for petroleum resource of Nanpu Sag in Bohai Bay Basin. Acta Petrolei Sin., 2005, 26(suppl.), 58–63 (in Chinese with English abstract).
25. Zheng, H. J., Dong, Y. X., Zhu, G. Y., Wang, X. D., Xiong, Y. High-quality source rocks in Nanpu Sag. Petroleum Exploration and Development, 2007, 34(4), 385–450 (in Chinese with English abstract).
26. Zhu, G. Y., Zhang, S. C., Dai, J. X., Liang, Y. B., Jin, Q., Zhang, L. Y. Accumulation periods of hydrocarbon and its distribution in Dongying Sag, Jiyang Depression, Eastern China. In: Petroleum Geochemistry and Exploration in the Afro-Asian Region (Liang, D. G., Wang, D. R., Li, Z. X., eds.). Taylor & Francis Group, Balkema, 2008, 47–58.
27. Zhu, G. Y., Zhang, S. C., Jin, Q., Dai, J. X., Zhang, L. Y., Li, J. Origin of the Neogene shallow gas accumulations in the Jiyang superdepression, Bohai bay basin. Org. Geochem., 2005, 36, 1650–1663.
http://dx.doi.org/10.1016/j.orggeochem.2005.08.009
28. Robbins, L. L., Blackwelder, P. L. Biochemical and ultrastructural evidence for the origin of whitings: A biologically induced calcium carbonate precipitation mechanism. Geology, 1992, 20(5), 464–468.
http://dx.doi.org/10.1130/0091-7613(1992)020<0464:BAUEFT>2.3.CO;2
29. Kelts, K., Hsu, K. J. Freshwater carbonate sedimentation. In: Lakes: Chemistry, geology, physics (Lerman, A., ed.). Springer-Verlag, Berlin, 1978, 295–320.
30. Dean, W. E. The carbon cycle and biogeochemical dynamics in lake sediments. J. Paleolimnol., 1999, 21, 375–393.
http://dx.doi.org/10.1023/A:1008066118210
31. Chen, J. A., Wan, G. J., Chen, Z. L., Huang, R. G. Chemical elements in sediments of Lake Erhai and palaeoclimate evolution. Geochimica, 1999, 28, 562–570 (in Chinese with English abstract).
32. Kilham, P. Mechanisms controlling the chemical composition of lakes and rivers: data from Africa. Limnol. Oceanogr., 1990, 35(1), 80–83.
http://dx.doi.org/10.4319/lo.1990.35.1.0080
33. Deng, H. W., Qian, K. The genetic types and association evolution of deep lacustrine faces mudstones. Acta Sedimentologica Sinica, 1990, 8(3), 1–21 (in Chinese with English abstract).
34. Zheng, H. J., Dong, Y. X., Wang, X. D., Zhang, S. C., Zhang, D. J., Zhu, G. Y., Xiong, Y., Yu, H. D. The generation and characteristics of source rocks in Nanpu oil-rich Depression, Bohai Bay Basin. Natural Gas Geoscience, 2007, 18(1), 78–83 (in Chinese with English abstract).
