LAWYER, GARY1 and ALAN P. BYRNES2
1Consultant, St. George, UT
2Kansas Geological Survey, Lawrence, KS
Abstract: Removed Overburden and Maturation Analysis of the Arkoma Basin and Ouachita Foldbelt, Oklahoma and Arkansas
Removed overburden analysis and calculations of thermal maturity, using burial and thermal history reconstruction, were performed for 115 wells across the Arkoma Basin and Frontal Ouachita Foldbelt. Results indicate that maturity in this region can be explained using models that are largely controlled by depth of burial and paleo-geothermal gradients similar to present-day gradients. Increasing maturation from west to east across the basin can be explained by increasing Atokan and Desmoinesian strata overburden and subsequent Mesozoic and Cenozoic surface erosion and does not appear to be due to Mesozoic intrusions or hydrothermal fluid migration. Removed overburden increases from 5,000 ft on the north flank of the basin to 15,000 ft along the southern basin axis. As much as 25,000 to 40,000 ft have been removed from the core of the Ouachita Foldbelt. Analysis indicates that most of the basin is over-mature for oil production from intervals below the Spiro Sandstone except to the north and northwest on the Oklahoma Platform. Except for the basal Arbuckle Group, all formations were immature prior to burial by northeastward prograding depocenters of Mississippian- and Morrowan-age sediments in the Ouachita Foldbelt of Oklahoma and by the Atokan- and Desmoinesian-age sediments over most of the Arkoma Basin. In most areas, strata entered the oil generation window during or immediately after Atokan deposition. In most areas, these same strata entered the dry gas window with 1 to 10 million years after onset of oil generation. Producing gas appear to have been emplaced as oil, cracked to gas, and trapped during this brief time period.
AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas