Paleogeomorphologic Reconstruction, Evolution, and Sedimentary System Control on Wenchang Formation in Enping 12 Sub-sag, Eastern Pearl River Estuary Basin

doi:10.19657/j.geoscience.1000-8527.2020.036

Abstract

Abstract:

Lacustrine sedimentation of the Enping 12 sub-sag was developed in the Paleocene Wenchang Formation.The lacustrine-facies sediments were substantially modified by a combination of tectonism and magmatism, which severely hampers source rock identification and hydrocarbon exploration. Based on paleogeomorphologic reconstruction with trend extrapolation, the relation between paleogeomorphologic evolution and sedimentary depression of the Enping 12 sub-sag is revealed. The results indicate that: (1) The Enping 12 sub-sag is a typical half-graben in the Wenchang Formation that was intensely denudated. The main denudation occurred in the braided river delta deposits and shore-shallow lacustrine deposits in the lacustrine basin gentle slope zone. (2) The fan bodies are located in the steep slope zone.Based on this study, well A was drilled and oil-bearing sequence was discovered, which confirms that Enping 12 sub-sag is a potential deep lacustrine hydrocarbon source. It also demonstrates the reliability and importance of paleogeomorphic reconstruction in studying sedimentary infill of modified depressions, and provides insight on estimating hydrocarbon resource potential for strongly modified depressions in the eastern Pearl River Estuary basin.

Key words: Pearl River Estuary Basin, Wenchang Formation, reconstruction, Enping 12 sub-sag

CLC Number:

LUO Ze, YAN Zhenghe, XIE Mingying, LIANG Jie, WU Jing. Paleogeomorphologic Reconstruction, Evolution, and Sedimentary System Control on Wenchang Formation in Enping 12 Sub-sag, Eastern Pearl River Estuary Basin[J]. Geoscience, 2020, 34(04): 710-717.

Figures/Tables 7

Fig.1 Location of Enping 12 sub-sag and tectonic division of Enping sag[1]

Fig.2 Types of stratigraphic erosion and reconstruction methods in Enping 12 sub-sag(Lower Wenchang Formation)

Fig.3 Palaeogeomorphology of Wenchang Formation in Enping 12 sub-sag

Fig.4 Seismic facies for vertical source direction of No.1(a), No.2(b) and No.3(c) valleys and along source direction of No.3 valley (location of profiles seeing Fig.3)

Fig.5 Relationship between seismic reflection structure and sedimentary response of Wenchang Formation in Enping 12 sub-sag(locations of profiles seeing Fig.1)

Fig.6 Sedimentary distribution of the lower and upper Wenchang Formation in Enping 12 sub-sag

Fig.7 Geochemical characteristics of hydrocarbon extracted from sidewall cores of Enping Formation in well A

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