Major Low-Permeability-Sandstone Gas Reservoirs in the Continental United States

This report summarizes geologic, engineering, and production information on 24 low-permeability, gas-bearing sandstone reservoirs in 13 basins in the United States. The information compiled in this report comes from publicly available sources: Gas Research Institute and Department of Energy project reports, applications by gas producers to state regulatory agencies for tight formation designation, and published literature. The formations included in this volume were selected because they contain abundant natural gas resources or because detailed information is known about them that is applicable to other, similar formations. Assessment of these sandstone reservoirs indicates that geological controls play a critical role in gas producibility and that many of these reservoirs share a number of key geological attributes.As it does in conventional oil and gas fields, reservoir genesis clearly influences gas accumulation and recovery in tight gas fields. The major tight gas sandstone reservoirs surveyed herein were deposited in 10 barrier/strandplain and 7 deltaic depositional systems. Four fluvial, three shelf, and one slope and basin, and fan-delta depositional system make up the remainder. Production characteristics of low-permeability gas reservoirs are, however, in large part controlled by the diagenesis of the sediment. In these 24 formations, authigenic quartz and clays have the greatest effect on reducing permeability, quartz by occluding intergranular pores and clays by increasing water saturation because of their high surface-to-volume ratio. Calcite cement destroys porosity and permeability in particular beds or layers in some formations, but its distribution is not as uniform or widespread as that of quartz cement.Natural fractures are common features of tight gas sandstones, but because most are vertical extension fractures that are easily missed by vertical cores, detailed information on natural fracture attributes is rarely available. Fractures can enhance production, and in some formations they need to be taken into account in drilling, completion, and stimulation design. Information on stress directions and stress contrasts in low-permeability sandstone reservoirs is also important for designing engineering operations in these rocks. Available data on natural fractures, stress directions, and stress-magnitude contrasts are summarized for each formation.Twenty-one of the 24 low-permeability formations discussed in this volume have produced 22.3 Tcf of gas through 1988; this figure does not include production from the '*Clinton"-Medina and Berea Sandstones in the Appalachian Basin or the Davis sandstone in the Fort Worth Basin. Estimated ultimate recovery from existing wells in the 21 formations for which compiled production data are available is 47.1 Tcf.
Shriley P. Dutton
Sigrid J. Clift
Douglas S. Hamilton
H. Scott Hamlin
Tucker F. Hentz
William E. Howard
M. Saleem Akhter
Stephen E. Laubach

Dutton, S. P., Clift, S. J., Hamilton, D. S., Hamlin, H. S., Hentz, T. F., Howard, W. E., Akhter, M. S., and Laubach, S. E., 1993, Major Low-Permeability-Sandstone Gas Reservoirs in the Continental United States: The University of Texas at Austin, Bureau of Economic Geology, Report of Investigations No. 211, 221 p.

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The University of Texas at Austin, Bureau of Economic Geology
Report of Investigation