Petroleum Charge to the Mill Creek Syncline and Adjacent Areas, Southern Oklahoma
A. A. Brown
Consultant, Richardson, TX
Woodford-generated oil is produced from fields in the Mill Creek Syncline, north of the Arbuckle Uplift, yet none of the preserved Woodford source rock in the syncline is thermally mature. The burial and tectonic history of the Ardmore Basin and Arbuckle Uplift were analyzed to understand where this oil came from.
Geohistory models of the deep Ardmore Basin demonstrate that Woodford oil generation initiated during Early Desmoinesian, reached peak oil window by middle Desmoinesian, and entered the gas generation zone during Late Pennsylvanian. An estimated 40 billion barrels of oil were generated from the Woodford Formation in the central and eastern Ardmore Basin.
Uplift of the Arbuckle Anticline and related structures initiated
during Late Desmoinesian, after initiation of Woodford oil generation
in the Ardmore Basin. Ardmore Basin oil generated before uplift
could migrate to the Mill Creek Syncline by updip, stratal migration
.
After Late Desmoinesian deformation, the
migration
pathway
was
destroyed, and north-migrating oil seeped to the surface south of the
uplifts. Woodford oil charge to the Mill Creek Syncline could only
have occurred during the Desmoinesian. Stratigraphic evidence supports
this timing. The Buckhorn asphalt is actually a sea-floor oil seep
of Early Middle Desmoinesian age, demonstrating petroleum
migration
at this time. Major asphalt deposits are truncated by Late Virgilian
strata, indicating charge prior to late Virgilian. Asphalt deposits
form a
migration
chain documenting south to north
migration
.
Almost all Woodford-sourced oil accumulations in Southern Oklahoma
date from the Pennsylvanian or Early Permian. Although
Woodford shale over much of the western Ardmore Basin is now in
the oil window, generation and migration
since the Pennsylvanian
has been negligible due to absence of renewed burial. Characteristics
of older accumulations include large seepage anomalies, incomplete
fill due to longer duration of leakage, and thick residual saturation
zones which make identification of productive zones more difficult.
AAPG Search and Discovery Article #90905©2001 AAPG Southwest Section Meeting, Dallas, Texas