Geological Setting of Small County

Small County is located in the central United States with a small farming community and a county seat of Smallville. Oil production from a number of small fields is second only to agriculture as a source of income. The surface geology of Small County consists of Cretaceous sandstones and shales.

Small County Surface Geology

Exploration drilling searches for oil in the subsurface in the Quivira Dolomite (Permian), Westport Limestone (Pennsylvanian), Morn Sandstone (Pennsylvanian), and Sawyer Sandstone (Cambrian).

Small County Stratigraphic Column

In every well you drill, you can expect to see the entire stratigraphic sequence shown above, except perhaps the Morn and Sawyer Sandstones. These sandstones were deposited in channels incised into the underlying formations (the Ordovician Dolomite or the Precambrian) and may or may not be encountered in a particular well. You should also be aware that the Francisco and Possum Trot Shales, shown in black above, are "hot" shales, meaning they have a relatively high content of radioactive isotopes and therefore higher gamma ray readings (around 160 API units) than the other shales in the sequence (120-130 API units). Otherwise they are indistinguishable from the shales that alternate with the dolomites and limestones in the overlying intervals.