In a 3-D seismic survey, we acquired data over an 8-mi2 section of Cut Bank field, located on the west flank of Sweetgrass Arch in Glacier County, Montana. The main objective of the study was to improve the results of an ongoing waterflood program. The targeted reservoirs were an alluvial braided-stream system having a gross sand thickness of 20 to 25 ft. These reservoirs were deposited as incised-valley systems that are now at a depth of approximately 3,000 ft.

Because specific-capacity data are useful for estimating transmissivity, they should be used whenever possible in hydrogeologic studies. Including specific-capacity data will increase the number of transmissivity estimates in aquifers, sometimes dramatically, allowing more accurate statistical and spatial descriptions of transmissivity and hydraulic conductivity. Three main approaches are used in estimating transmissivity from specific capacity data: analytical, empirical, and geostatistical.

This report presents a statistical analysis of outcrop-permeability data for quantifying spatial patterns of petrophysical heterogeneity in carbonates that are difficult or impossible to observe in the subsurface. In the study, workers made permeability measurements using plug samples and mechanical field permeameters (MFP) from Permian and Cretaceous shallow-water platform carbonate outcrops in West Texas and New Mexico. The report includes a detailed discussion of factors affecting the accuracy of the measurements and the portability of resulting spatial statistics to subsurface studies.