Petrophysics of Medina and Tuscarora Sandstones and Integration with the Tectonic-Stratigraphic Framework, Appalachian Basin, U.S.A.
Castle, James W. 1 and Byrnes, Alan P. 2
1Clemson University, Department of Geological Sciences, Clemson, South Carolina
2Kansas Geological Survey, Lawrence, Kansas
Petrophysical properties were determined for six facies in Medina and Tuscarora sandstones of the Appalachian basin: fluvial, estuarine, upper shoreface, lower shoreface, tidal channel, and tidal flat. Fluvial sandstones have the highest permeability for a given porosity and exhibit a wide range of porosity (2-18%) and permeability (0.002-450 md). With a transition-zone thickness of only 3-20 feet, fluvial sandstones with permeability greater than 5 md have irreducible water saturation (Siw) less than 20%. Upper shoreface sandstones exhibit good reservoir properties with high porosity (10-21%), high permeability (3-250 md), and low Siw (<20%). The other sandstone facies have lower porosity, lower permeability, thicker transition zones, and higher Siw.
The most favorable reservoir petrophysical properties and the best estimated production from the Lower Silurian sandstones are associated with fluvial and upper shoreface facies of incised-valley fills, which we interpret to have formed predominantly in areas of structural recesses that evolved from promontories along the collisional margin associated with the Taconic orogeny. Although the total thickness of sandstone may not be as great in these areas, reservoir quality is better than in adjacent structural salients, which is attributed to higher energy depositional processes and shallower maximum burial depth in the recesses than in the salients.