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Once it has been determined that a meandering fluvial model is applicable to a formation, paleohydrologic reconstructions can be applied to downhole measurements to derive sand body widths. The nonmarine part of the Mesaverde Formation in the east-central part of the Piceance Creek basin of northwestern Colorado was deposited in a predominantly meandering fluvial
system. This interpretation is based on the presence of lateral accretion beds and multi-story sand bodies in outcrops along the Grand Hogback. It is supported by fining-upward trends in cores and gamma ray logs from the wells of the U.S. Department of Energy's Multi-Well Experiment being conducted near Rifle, Colorado.
Paleochannel depths, recognized from the heights of fining-upward trends in cores, can be converted to channel widths using Leeder's 1973 formula. The resulting channel widths are used to calculate meander belt amplitudes (sandstone body widths) from relationships derived from Leopold and Wolman's 1960 empirical data.
These numbers can be compared with sandstone body widths derived by two other methods. (1) Point-bar dimensions measured in outcrops can be used to calculate channel widths, which are then converted to meander-belt amplitudes as described above. (2) The MWX-2 well is offset from MWX-1 by 135 ft (41 m) at the surface, allowing for positive well-to-well correlation of sandstones. The percentage of sandstones which are penetrated by both wells is used as a probability to derive an average sand body width.
These last two methods give compatible results. The first method described, however, predicts comparatively narrow widths, suggesting that channel depths derived from fining-upward sequences in cores are not fully representative of ancient channel depths due to incomplete preservation. A preservation potential factor may be added to Leeder's formula for working with ancient sediments, so that the formula gives comparable results to the other two methods.
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