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The Moenkopi Formation contains estimates of over 1 billion bbl of oil in the northwestern part of the Paradox basin in Emery, Garfield, and Wayne Counties, Utah. The Moenkopi is comprised of four members. The basal unit, the Black Dragon Member, is the most variable member in thickness as a result of infilling topographic relief of the post-Permian topography. The upper three units--the Sinbad, Torrey, and Moody Canyon Members, in ascending order--are principally marine deposits that thicken to the west. The distribution of the underlying Permian units appears to have controlled, in part, the deposition of the Black Dragon Member, with perhaps the Paradox evaporites of Pennsylvanian age adding to the control of the deposition. The Emery uplift did not influence depositio of the Moenkopi, and had ceased influencing deposition of units by the time the Permian White Rim was deposited.
The origin of the oils in the Moenkopi Formation is still open to debate. The writer believes that due to the presence of a high percentage of marine rocks, the tight and discontinuous nature of the reservoir rocks, and the character of the oils from the Moenkopi, the source rocks for the oils in the Moenkopi are contained within the Moenkopi Formation. Generation of hydrocarbons occurred in the areas near the accumulations with limited migration distances being necessary.
By combining surface and subsurface data on the underlying Permian units, the Moenkopi Formation, and the overlying Upper Triassic Chinle Formation, a more complete stratigraphic and depositional framework for the Moenkopi Formation is possible. The result is a better understanding of the surface accumulations and a better exploration strategy for subsurface accumulations.
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