| [[file:M91FG177.JPG|thumb|300px|{{figure number|6}}Upward-decreasing permeability profile in a point bar sandstone in the Peoria field, Colorado (from Chapin and Mayer<ref name=Chapinandmayer_1991>Chapin, M. A., and D. F. Mayer, 1991, [http://archives.datapages.com/data/sepm_sp/csp3/Constructing_a_Three-DimensionalOp.htm Constructing a three-dimensional rock property model of fluvial sandstones in the Peoria field, Colorado], in A. D. Miall and N. Tyler, eds., The three dimensional facies architecture of terrigenous clastic sediments and its implication for hydrocarbon discovery and recovery: SEPM Concepts in Sedimentology and Paleontology 3, p. 160–171.</ref>). Reprinted with permission from, and © by, the SEPM (Society for Sedimentary Geology).]] | | [[file:M91FG177.JPG|thumb|300px|{{figure number|6}}Upward-decreasing permeability profile in a point bar sandstone in the Peoria field, Colorado (from Chapin and Mayer<ref name=Chapinandmayer_1991>Chapin, M. A., and D. F. Mayer, 1991, [http://archives.datapages.com/data/sepm_sp/csp3/Constructing_a_Three-DimensionalOp.htm Constructing a three-dimensional rock property model of fluvial sandstones in the Peoria field, Colorado], in A. D. Miall and N. Tyler, eds., The three dimensional facies architecture of terrigenous clastic sediments and its implication for hydrocarbon discovery and recovery: SEPM Concepts in Sedimentology and Paleontology 3, p. 160–171.</ref>). Reprinted with permission from, and © by, the SEPM (Society for Sedimentary Geology).]] |
− | Fining-upward profiles are typical for point bars; the permeability declines upward with decreasing grain size ([[:file:M91FG177.JPG|Figure 6]]). The decrease in permeability commonly occurs in a step-like fashion rather than showing a gradual upward decrease. | + | Fining-upward profiles are typical for point bars; the permeability declines upward with decreasing [[grain size]] ([[:file:M91FG177.JPG|Figure 6]]). The decrease in permeability commonly occurs in a step-like fashion rather than showing a gradual upward decrease. |
| Upward-decreasing permeability profiles are unfavorable to efficient sweep. Water will flood through the high-permeability basal part of the point bar leaving the uppermost section unswept ([[:file:M91FG176.JPG|Figure 5b]]). | | Upward-decreasing permeability profiles are unfavorable to efficient sweep. Water will flood through the high-permeability basal part of the point bar leaving the uppermost section unswept ([[:file:M91FG176.JPG|Figure 5b]]). |