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Fluvial Models in Coal and Hydrocarbon Exploration: Abstract
Channel and levee deposits are important components of fluvial-deltaic sequences and are economic factors in the exploration and exploitation of oil and gas in the Tertiary deposits of the Gulf Coast and of coal in the Carboniferous of the Appalachians.
In the transitional zone between lower and upper delta plain sequences of the Tertiary deposits, infrequent, laterally migrating, meandering channels developed. Fine-grained point bar deposits accumulated in single-storied sequences within these channels. Associated with these deposits are brackish to marine shales and siltstones with good source quality organic matter, and because of this, these channels become reservoir targets.
However, producing hydrocarbons from fine-grained reservoirs can be difficult. Within the point bar sequences individual sandstone beds may be separated and sealed by thin shale beds. Selected multiple perforations must be made for the individual sandstone lenses or much of the hydrocarbons in the reservoir will be left untapped.
In the Carboniferous, channels that occurred directly over a coal often scoured downard onto the coal reducing its thickness and, in some instances cut it out entirely. The sandstones of channel deposits that rest directly on coals can provide excellent roof rock in mines, but when slump blocks that accumulate most abundantly on the “cut bank” side of channels are encountered, severe roof problems develop.
Levee deposits can cause splits in coal seams that reduce coal thickness below minable minimums and increase the percent rejects above tolerable limits. Where extensively rooted levees occur directly over a minable coal, severe roof problems are encountered.
Because of their effect on economic parameters of hydrocarbons, channel and levee deposits must be considered during the exploration phase with respect to drill hole spacing in order to delineate these features. In addition, these deposits must be taken into account during the exploitation phase to provide the maximum development of reservoir potential for oil and gas and during the mine planning and development for coal because of potential roof problems they may cause.
Acknowledgments and Associated Footnotes
1 Department of Geology, University of South Carolina, Columbia, South Carolina 29208
2 The Superior Oil Company, 700 Saratoga Building, New Orleans, Louisiana 70112
Copyright © 2009 by the Canadian Society of Petroleum Geologists