Sedimentation and hydrocarbon accumulation of deep-water fan fed by large canyon in passive continental margin: a case of Congo fan in West Africa

doi:10.3969/j.issn.1672-7703.2018.06.007

Abstract

Abstract: Deep-water fan fed by large canyon in passive continental margin is a typical type of deep-water fan. Deep understanding of the sedimentary and hydrocarbon accumulation characteristics is of significance for other deep-water fans of the same type in the world. Analysis of survey data indicates that the Quaternary Congo fan is superimposed by dissected northern, southern and axial fans, and each fan has a variety of turbidite systems. In the east-west direction, the fan is dominated by marine progradation and the depocenter of the channel systems in the fan migrated about 100km. In the south-north direction, the fan migrated from north and south to center, so the turbidite system migrated counterclockwise in the northern fan, clockwise in the southern fan, and from SE to NW in the axial fan. The architectural elements are mainly composed of channel levee and frontal lobe, which present a branch-leaf network. Allogenic factors such as source system, climate and salt rock deformation, control the fan development. Further analysis shows that the ancient Congo fan has similar sedimentary characteristics with the Quaternary Congo fan. The Congo fan has good hydrocarbon accumulation conditions based on statistical analysis. The source rock is the Cenomanian-Maastrichtian marine shale; the reservoir is composed of the Oligocene-Miocene channel or complex sandstone; and the hydrocarbon is blocked locally by the shale interlayer and accumulates in the stratigraphic-structural and stratigraphic traps. At present stage, exploration is suggested on the incised channels on the shelf margin and net crevasse channels in the upper fan on the canyon edge.

Key words: passive continental margin, West Africa, deep-water fan, channel levee, Congo fan, Zaire canyon

CLC Number:

Qin Yanqun, Ba Dan, Xu Hailong, Liang Yingbo, Yang Zi, Liang Xu, Wang Xinglong. Sedimentation and hydrocarbon accumulation of deep-water fan fed by large canyon in passive continental margin: a case of Congo fan in West Africa[J]. China Petroleum Exploration, 2018, 23(6): 59-68.

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