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