Frio Formation, Texas Gulf Coast

General Setting

The Gulf Coast is an attractive target for CO₂ sequestration because of the coincidence of emitters (industrial and power-generation facilities) and potential sinks in a thick young wedge of sand-rich sediment. Gulf Coast sandstones are also extensively used for underground injection of chemical and other wastes (Kreitler and others, 1988). During the Tertiary Period, wedges of sediments shed from the rising mountains of the western U.S. and Mexico were deposited in coastal-plain and offshore environments. Sand-rich facies include river-channel, delta-mouth-bar, barrier, slope-channel, and fan environments. Growth faulting resulting from loading of clays by sand created accommodation for accumulation of exceptionally thick sands. Episodes of relative sea-level rise flooded the area and caused widespread accumulation of clay. Complex interactions among sea level, coastal process, and sediment supply have led to complexity within this thick sedimentary unit.

Information Search and Selection

The number of possible sinks along the Gulf coast is a challenge for this project because the total sand volume and the diversity of potential targets are very large. We selected two units, the upper Frio and the Oakville-Lagarto, as examples of good targets. As is true of other basins in this study, a number of formations are potential targets in the area; Wilcox, Claiborne, and Jackson Groups beneath the Frio contain numerous suitable targets in the updip (western and northern parts of the Gulf Coast basin), and Pliocene and Pleistocene units may be thick enough to be considered near the coast. Nomenclature is a barrier to understanding the options in target selection. Because of the areal extent of the depositional basin, complex depositional environments, and stratigraphic complexities resulting from growth faulting, definition of stratigraphic units is complex and controversial. We have followed the stratigraphy of Galloway and others (1982), which includes the Texas Catahoula, Frio, and Vicksburg as part of one major genetic unit. We incorporated four large volumes of information about the Frio at regional and field scales; the challenge was to extract suitable and reasonably consistent basin-scale information. In this highly heterogeneous and complex formation, field-specific information is required as a follow-up to this regional-scale study.

Comments on Geologic Parameters

1. Depth:	10. Fluid Residence Time:
2. Permeability/Hydraulic Conductivity:	11. Flow Direction:
3. Formation Thickness:	12. CO2 Solubility Brine	12a. Temperature:
4. Net Sand Thickness:		12b. Pressure:
5. Percent Shale:		12c. Salinity:
6. Continuity:	13. Rock/Water Reaction:
7. Top Seal Thickness:	14. Porosity:
8. Continuity of Top Seal:	15. Water Chemistry:
9. Hydrocarbon Production:	16. Rock Mineralogy:

References

Capuano, R. M., 1993, Evidence of fluid flow in microfractures in geopressured shales: American Association of Petroleum Geologists Bulletin, v. 77, no. 8, p. 1303–1314.

Galloway, W. E., Ewing, T. E., Garrett, C. M., Tyler, Noel, and Bebout, D. G., 1983, Atlas of major Texas oil reservoirs: The University of Texas at Austin, Bureau of Economic Geology, 139 p.

Galloway, W. H., Hobday, D. K., and Magara, Kinji, 1982, Frio Formation of the Texas Gulf Coast Basin—depositional systems, structural framework, hydrocarbon origin, migration, distribution, and exploration potential: The University of Texas at Austin, Bureau of Economic Geology Report of Investigations No. 122, 78 p.

Harrison, W. J., and Summa, L. L., 1991, Paleohydrology of the Gulf of Mexico basin: American Journal of Science, v. 291 p. 109–176.

Holtz, M. H., 1997, Oil atlas database of major Texas reservoirs: The University of Texas at Austin, Bureau of Economic Geology, Internal Report.

Knox, P. R., Holtz, M. H., McRae, L. E., Hentz, T. F., Paine, J. G., White, W. G., and Chang, C.-Y., 1996, Revitalizing a mature oil play: strategies for finding and producing unrecovered oil in Frio fluvial-deltaic sandstone reservoirs of South Texas: The University of Texas at Austin, Bureau of Economic Geology, final report prepared for U.S. Department of Energy, Bartlesville Project Office, under contract no. DE-FC22-93BC14959, 178 p.

Kreitler, C. W., Akhter, M. S., Donnelly, A. C. A, and Wood, W. T., 1988, Hydrology of formations for deep-well injection, Texas Gulf Coast: The University of Texas at Austin, Bureau of Economic Geology, unpublished contract report, 204 p.

Kreitler, C. W., and Richter, B. C., 1986, Hydrochemical characterization of the saline aquifers of the Texas Gulf Coast used for disposal of industrial waste: The University of Texas at Austin, Bureau of Economic Geology, unpublished contract report, 164 p.

Land, L. S., and Macpherson, G. L., 1992, Origin of saline formation waters, Cenozoic section, Gulf of Mexico sedimentary basin: American Association of Petroleum Geologists Bulletin v. 76, p. 1344–1362.

Loucks, R. G., Dodge, M. M., and Galloway, W. E., 1984, Regional controls on diagenesis and reservoir quality in lower Tertiary sandstones along the lower Texas Gulf Coast, in McDonald, D. A., and Surdam, R. C., eds., Clastic diagenesis: American Association of Petroleum Geologists Memoir 37, p. 15–46.

Macpherson, G. L., 1992, Regional variation in formation water chemistry; major and minor elements, Frio Formation fluids, Texas: American Association of Petroleum Geologists Bulletin, v. 76, no. 5, p. 740–757.

Morton, R. A., and Land, L. S., 1987, Regional variations in formation water chemistry, Frio Formation (Oligocene), Texas Gulf Coast: American Association of Petroleum Geologists Bulletin, v. 71, no. 2, p. 191–206.

National Imagery and Mapping Agency, 2000, Digital terrain elevation data (DTED Level 0), http:/www.gisdatadept.com.

Prepared by S. Hovorka.