ABSTRACT

Sumatra Field is far larger than the average Tyler (Pennsylvanian) field, and the sheer quantity and density of well control provides a great deal of information about the geometry of Tyler sand bodies that can be applied to other fields and prospects.

Tyler sands normally have a "shoe-string" geometry typical of Pennsylvanian sands in the Mid-Continent region. Most Tyler sands are approximately 1/4 mi (0.4 km) wide [one spacing unit of 40 ac (16 ha)], and 1-3 mi (1.6-4.8 km) long. They are elongated mostly parallel to the isopach lines in the Tyler channel system, most commonly near the thickest portion of the channel. The excellent marker beds of the underlying Heath (Mississippian) Formation and deep erosional cutting of the Tyler into Heath [up to 300 ft (91 m)] allow easy mapping of most of the channel system. However, marker beds within the Tyler are subtle to absent, except in the sand-poor highest section; thus correlation within the Tyler is more difficult.

Sumatra Field owes its immense size to two major episodes of faulting. Normal faulting down-dropped the Sumatra area relative to the block to the north during the time of deposition for the Heath and Tyler Formations. Stratigraphic members of the Heath Formation dearly thicken on the Sumatra block, and source quality may also improve. More importantly, faulting focused Tyler sand deposition on the down-thrown half-graben. Much later, Laramide reverse faulting inverted the fault blocks, creating a large anticline containing the thick sand and source rock beds.