Frio formation

The Frio formation, in Texas, receives more hazardous waste by volume through deep-well injection than any other geologic formation in the U.S. The average salinity of this formation is about twice that of seawater (72,185 mg/L TDS), but individual samples range from a low of 10,528 mg/L TDS (barely above the salinity cutoff for potential USDWs) to a high of more than 118,000 mg/L TDS. Data from sites in Illinois and North Carolina indicate the presence of very saline water (around 20,000 mg/L TDS, but still less saline than seawater). 

The pH of formation waters in the Frio formation varies widely from moderately acidic (5.7) to moderately alkaline (8.2), with nearly neutral averages (6.8). The pH of formation waters from other injection sites tends to be more alkaline, ranging from slightly alkaline (Belle Glade, Florida, pH 7.5) and moderately alkaline (Wilmington, North Carolina, pH 8.6), to very alkaline (Marshall, Illinois, pH 7.1 to 10.7). 

Doughty C., Pruess K., et al. Capacity investigation of brine-bearing sands of the Frio-formation for geological sequestration of C02. In Proceedings of First National Conference on Carbon Sequestration. 2001 U.S. Department of Energy. 

KharakaY.K., Cole D.R., et al. Gas-water-rock interactions in Frio formation follow-ing C02 injection implication for the storage of greenhouse gase in sedimentary basins. 2006 Geology 34 577-580. 

Lindquist S.J. (1977) Secondary porosity development and subsequent reduction, overpressured Frio Formation Sandstone (Oligocene), South Texas. Trans.-Gulf Coast Assoc. Geol. Socs. 27, 99-107. 

Lundegard P.D., Land L.S. and Galloway W.E. (1984) Problem of secondary porosity Frio Formation (Oligocene), Texas Gulf Coast. Geology 12, 399-402. 

Land L. S. and Fisher R. S. (1987) Wilcox sandstone diagenesis, Texas Gulf Coast a regional isotopic comparison with the Frio Formation. In Diagenesis of Sedimentary Sequences, Geological Society of America Special Pubh-cation 36 (ed. 1. D. Marshall). Geological Society of America, Boulder, CO, pp. 219-235. 

Macpherson G. L. (1992) Regional variation in formation water chemistry major and minor elements, Frio Formation fluids, Texas. Am. Assoc. Petrol. Geol Bull 76, 740-757. 

Figure 3 Dissolution is a surface-reaction controlled process throughout late diagenesis (a) dissolution of an epidote grain from the subsurface Plio-Pleistocene sequence offshore Louisiana SEM image and (b) Ca-plagioclase, Frio Formation, Oligocene, South Texas, SEM image ((a) is reproduced by permission of SEPM (Society for Sedimentary Geology) from J. Sedim.

Figure 6 Patchy calcite (c) replacing detrital feldspar (now albite, ab) in sbale. Similar microscale distributions of replacement phases are observed widely in sandstones and sbales. Frio Formation, Oligocene, South Texas. Backscattered electron image.

Figure 7 Replacement driven by force-of-crystal-Uzation is characterized by authigenic phases that develop euhedral faces that are not plausibly constmed as crystal growth within pore spaces (a) sphalerite replaces albitized detrital feldspar and adjacent portions of clay-rich matrix, Frio Formation, Oligocene, South Texas and (b) siderite crystal (s) attacks a detrital K-feldspar (K) in sandstone, Breathitt Formation, Pennsylvanian, eastern Kentucky.

The difficulties imposed by clay coatings on quartz nucleation probably explain why there are few reports of quartz cementation in shales. The oxygen in quartz silt is isotopically heavy (8 0 = 19%o) compared to sand-size quartz (5 0 = 14%o) (Blatt, 1987) suggesting that a substantial component of relatively low-temperature quartz resides in shales. The application of cathodoluminescence microscopy to shales has been quite limited. In Frio Formation shales of south Texas no convincing quartz cement is observed across a range of depths in which quartz cementation becomes important in associated... 

Freed R. L. (1982) Clay mineralogy and depositional history of the Frio Formation in two geopressured wells, Brazoria County, Texas. Gulf Coast Assoc. Geol. Soc. Transac. 32, 459-463. 

Land L. S. and Milliken K. L. (1981) Feldspar diagenesis in the Frio Formation, Brazoria County, Texas Gulf Coast. 

Lynch F. L. and Land L. S. (1996) Diagenesis of calcite cement in Frio Formation sandstones and its relationship to formation water chemistry. J. Sedim. Res. A66, 439-446. 

Milliken K. L. (1992) Chemical behavior of detrital feldspars in mudrocks versus sandstones, Frio Formation (Oligocene), South Texas. J. Sedim. Petrol. 62, 790-801. 

Sullivan K. B. and McBride E. F. (1991) Diagenesis of sandstones at shale contacts and diagenetic heterogeneity, Frio Formation, Texas. Am. Assoc. Petrol. Geologists Bull. 75, 121-138. 

Kaiser, W.R. (1984) Predicting reservoir quality and diagenetic history in the Frio Formation (Oligocene) of Texas. In Clastic Diagenesis (Ed. McDonald, D.A. Surdam, R.C.). Mem. Am. Ass. petrol. Geol., Tulsa, 37, 195-216. 

Lynch, F. (1997) Mineralogy of Frio Formation shales and the stoichiometry of the smectite to illite reaction— the most important reaction in sedimentary diagenesis. Clays Clay Miner., 45, 618-631. 

Milliken, K.L., McBride, E.F. Land, L.S. (1989) Numerical assessment of dissolution versus replacement in the subsurface destruction of detrital feldspars, Oligocene Frio Formation, South Texas. J. sediment. Petrol., 59, 740-757. 

Land, L.S. (1995) Na-Ca-Cl saline formation waters, Frio Formation (Oligocene), south Texas, USA products of diagenesis. Geochim. Cosmochim. Acta, 59,2163-2174. 

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