Wellman field, Terry County, Texas

The Wellman field produces from a limestone reef in the lower part of the Wolfcamp series of the Permian. This Wolfcamp reef was deposited upon a local feature of the extensive Pennsylvanian reef trend known as the Horseshoe atoll. Considerable structural relief is present in beds younger than the Wolfcamp reef limestone; however, beds older than the Pennsylvanian reef limestone are flat. Evidence is presented to show that the structure found above the Wolfcamp reef is not related to this reef, but directly to the Pennsylvanian reef. The difference in effect of the two reefs on the structural attitude of the younger rocks is found in the magnitude of contemporaneous deposition of the flank sedimentary rocks.