Formation
A named, mappable layer of rock with consistent characteristics — like the Wolfcamp or Bakken — often the producing interval listed on a drilling permit.
A formation is a distinct, mappable body of rock that geologists name and trace across a region because it shares a consistent rock type, or lithology, that sets it apart from the layers above and below. Familiar oil and gas examples include the Wolfcamp, Bakken, Marcellus, and Eagle Ford. The formation a well targets is usually written right on its drilling permit and on production filings.
For a mineral owner, the formation matters because your tract can have value at more than one depth. A lease may cover all formations, or a depth severance can split who owns the shallow rock versus the deep rock. Knowing which formation an operator is drilling tells you which of your rights are actually being developed.
Formations are geologic layers, not legal tracts — they cut across property lines and county boundaries. The same named formation can be a prolific producer in one part of a basin and barren a few miles away.