Oil & Gas Geology ›› 2023, Vol. 44 ›› Issue (3): 565-583.doi: 10.11743/ogg20230304

• Petroleum Geology • Previous Articles     Next Articles

Source-to-sink system and hydrocarbon source rock prediction of underexplored areas in rifted lacustrine basins: A case study on northern lows in Zhu Ⅰ Depression, Pearl River Mouth Basin

Hao LIU1(), Changgui XU2, Yangdong GAO3, Heming LIN3, Xinwei QIU3, Yongtao JU4, Xudong WANG3, Lei LI5, Jun MENG1, Xiaoming QUE3   

  1. 1.China University of Geosciences (Beijing),Beijing 100083,China
    2.China National Offshore Oil Corporation,Beijing 100010,China
    3.China National Offshore Corporation-Shenzhen Branch,Shenzhen,Guangdong 518054,China
    4.North China University of Science and Technology,Tangshan,Hebei 063210,China
    5.Xi’an Shiyou University,Xi’an,Shaanxi 710065,China
  • Received:2023-02-09 Revised:2023-04-16 Online:2023-06-01 Published:2023-06-05

Abstract:

Hydrocarbon source rock is one of the key factors controlling oil/gas accumulation in petroliferous system of a sedimentary basin. Focusing on the challenges facing hydrocarbon source rock prediction in basins or lows with relatively low exploration maturity, sparsely distributed drilling wells and insufficient source rock index, we take the underexplored areas in northern Zhu Ⅰ Depression in the Pearl River Mouth Basin (PRMB) as an example to systematically analyze the source-to-sink system and predict source rocks from the perspectives of “searching for lake (deep-to-semi-deep lake)”, “recognizing mudstones (deep-to-semi-deep lacustrine mudstones)”, and “identifying hydrocarbon (hydrocarbon source rock prediction and evaluation)”. First, the original basin features and location of the paleo-lacustrine basin are illustrated by restoring multi-stage tectono-palaeogeomorphology to “find the lake”; and the deep-to-semi-deep lake is identified in the underexplored area together with preliminary selection of potential lows with well-developed hydrocarbon source rocks in combination with analyses including “identifying the lacustrine basin boundary by seismic progradational reflection, determining the scope of the deep-to-semi-deep lake by slope break system, illustrating paleo-environment characters by biochemical index, and defining the lacustrine basin scale by tectonic intensity”. The results indicate that five lows formed during the Wenchang depositional period, and five lows formed during the depositional period of the lower Enping Formation have the potential of developing deep-to-semi-deep lacustrine mudstones. Second, the reconstruction of source-to-sink system and the geological analysis of deep-to-semi-deep lacustrine mudstone development are conducted through analyses of paleo-provenance, paleo-environment and depositional systems, as well as tectono-palaeogeomorphology features; various configuration elements simulation results of the source-to-sink system show that basins characterized by medium sediment supply intensity, fine-grained source materials, high lake level, large accommodation space and under-equal or equal compensation are favorable for the deposition of mud-rich lacustrine facies. Finally, based on data of exploratory wells encountering high-quality hydrocarbon source rocks in mature exploration areas, we analyze four types of deep-to-semi-deep seismic facies and their geologic backgrounds corresponding to hydrocarbon source rock intervals, establish the “hydrocarbon source rock facies (seismic facies of hydrocarbon source rocks)” of the mature exploration areas. Coupled with the systematic summary of hydrocarbon-enrichment factors in main hydrocarbon-rich lows of the Zhu Ⅰ Depression, we assess and rank the high-quality hydrocarbon source rocks in the underexplored areas with multiple factors and from multi-dimensional points of view. The research results also indicate that the first-order potentially hydrocarbon-rich lows include LF22, HF33, and HZ24 (with the lower and upper Wenchang Formation as source rocks), as well as the LF7 and HF10 (with the lower Wenchang Formation as source rocks); the second-order potentially hydrocarbon-rich ones are HZ5 and HZ11 (with the lower Enping Formation as source rocks), with the hydrocarbon source rock prediction and evaluation results of some lows having been testified in practical exploration.

Key words: seismic facies of source rocks, source rock prediction, underexplored area, source-to-sink system, Paleogene, Pearl River Mouth Basin (PRMB)

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