3-D seismic identification and characterization of ancient channel morphology

Abstract

It is easy to identify ancient fluvial morphologic types by the outcrop, log and core data. However, the horizontal distribution and geometry of the channels can only be identified and predicted by relying on the 3-D seismic data. The 3-D seismic horizon slices, especially, can play an important role in the sandstone prediction of meandering rivers, distributary channels and low-sinuosity channels. Every microfacies unit, including main channels, such as sinuous or branching channels, levee, crevasse channels, ligule crevasse splay and floodplain etc. can be identified. Braided channel sandstones are planar tabular lateral-connected sandbodies and the distribution of thick main channel belts can only be identified from 3-D seismic data. As the braided sandstones are ubiquitous, their occurrence and distribution do not need to be predicted. Generally, the coal velocity is so low that it can create a strong amplitude reflection in coal strata. It consequently conceals the amplitude respondence to anastomosing channel sandstone which could be identified from 3-D seismic inversion data sometimes. Case studies of mud-rich low-sinuosity rivers identified with 3-D seismic data indicate that the scales and width-to-thickness ratio of such sandbodies are small, laterally unconnected, and generally occurred on distant or further parts of an alluvial fan under dry climate conditions. Sometimes extraction of seismic attributes of every reflection event along horizons is expected to maximize expression of the spatial evolutions of ancient channels.

Keywords

sandbody identification / morphologic river type / 3-D seismic explanation / low-sinuosity channel

References

[1] Brown A. R.. Interpretation of Three-Dimensional Seismic Data. AAPG Mem., 1999, 42: 97-188.

[2] Galloway W. E., Hobday D. K.. Terrigenous Clastic Depositional Systems—Application to Petroleum, Coal, and Uranium Exploration, 1983, New York: Springer-Verlag 45-68.

[3] He F. Q., Zhai X. X., Yu R. L., . Deposition and Genetic Analysis of Carboniferous Kalashayi Formation in Tahe Oilfield. Oil and Gas Geology, 2004, 25(3): 258-262.

[4] McPherson J. G., Shanmngan G., Moiola R. J.. Fan-Deltas and Braided Deltas. Geol. Soc. Amer. Bull., 1987, 99: 331-340.

[5] Miall A. D.. A Review of the Braided-River Depositional Environment. Earth-Science Review, 1977, 13(1): 1-62.

[6] Pu R. H.. Preliminary Research on Investigating Relative Thickness of the Sand Body at the Bottom of Sangonghe Formation Using Seismic Amplitude Information. Geophysical Prospecting for Petroleum, 1994, 33(2): 66-74.

[7] Pu R. H.. The Typical Seismic Facies in Tahe Oilield. Oil Geophysics Prospecting, 2007, 42(3): 308-314.

[8] Pu R. H., Mei Z. C., Tang Z. H.. Seismic Facies Analysis of Xishanyao Formation in Eastern Junggar Basin. Petroleum Exploration and Development, 1993, 20: 57-60.

[9] Pu R. H., Mei Z. C., Tang Z. H.. Seismic Facies of Jurassic in Eastern Junggar, Xinjiang, China. Oil & Gas Geology, 1994, 15(3): 241-247.

[10] Pu R. H., Mei Z. C., Tang Z. H.. Division of Seismic Sequences and Interpretation on Sequence Stratigraphy of Shishugou Group, Cainan Area, Junggar Basin, Xinjiang, China. Earth Science—Journal of China University of Geosciences, 1994, 19(6): 769-777.

[11] Reynolds A. D.. Dimensions of Paralic Sandstone Bodies. AAPG, 1999, 83(3): 211-229.

[12] Wang S. J., Ren M. D.. A New Classification of Fluvial Rivers according to Channel Platform and Sediment Characteristics. Acta Sedimentologica Sinica, 1999, 17(2): 240-246.

[13] Wright V. P., Marriott S. B.. The Sequence Stratigraphy of Fluvial Depositional Systems: The Role of Floodplain Sediment Storage. Sedimentary Geology, 1993, 86(3–4): 203-210.

[14] Zhong H. L., Pu R. H., Han Q.. Braided River-Braided Delta Deposition of Sand Set Chang 10 of Yanchang Formation in LYD Area of Ordos Basin, North China. Science Journal of Northwest University Online, 2006, 4(1): 1-6.