Abstract

The Arkoma Basin, located in southeast Oklahoma and west-central Arkansas, is a Pennsylvanian basin which produces dry gas exclusively, primarily from stratigraphic traps in Atokan and Morrowan Sandstones.

Structurally, the basin contains three distinct units: (1) a shallow shelf with normal faulting only, (2) an intermediate shelf, characterized by normal and growth faulting and (3) a deep basin, characterized by growth and reverse faulting.

The growth faulting influenced Middle Atokan sedimentation, causing the deposition of additional section throughout the Middle Atokan. During the Morrowan and Atokan, a series of delta systems developed across the shelf of the basin, sourced mainly from the north and east. However, during the Middle Atokan, the delta systems were restricted to the shallow and intermediate shelf. Six distinct deltaic sequences were deposited during the Middle Atokan; the Alma, Lower Alma, Carpenter 'B', Morris, Tackett, and Areci. They are all variable in lateral extent, thickness, and depocenter location, but all have a north to northeast source and broad distribution along the shelf. The Alma has a much wider extent than the others as the deep basin had filled by the end of the Middle Atokan, allowing the delta system to spread southwest. Post-Pennsylvanian erosion has removed the upper distributary portion of the above systems.

All of the Middle Atokan Sandstones produce gas from stratigraphic traps within distributary mouth bars, barrier bars, and delta front sheet sands.